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Java™ Programmi ivCopyright 2007 Sun Mi

....................... Preface-xvi

...................................Preface-xvii

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...................................Preface-xxii

..................................Preface-xxiii

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ng Languagecrosystems, Inc. All Rights Reserved. Sun Services, Revision G.1

Course Contents

About This Course ..............................................................Course Goals ..........................................................................................Course Overview ..................................................................................Course Map ............................................................................................Topics Not Covered ..............................................................................How Prepared Are You? ......................................................................Introductions .........................................................................................How to Use the Icons ............................................................................Typographical Conventions and Symbols .......................................

Getting Started ....................................................................Objectives ...............................................................................................Relevance ................................................................................................What Is the Java™ Technology? .........................................................Primary Goals of the Java Technology ..............................................The Java Virtual Machine ....................................................................Garbage Collection ...............................................................................The Java Runtime Environment ..........................................................Operation of the JRE With a Just-In-Time (JIT) Compiler ..............JVM™ Tasks ..........................................................................................The Class Loader ...................................................................................The Bytecode Verifier ...........................................................................A Simple Java Application ...................................................................The TestGreeting Application .........................................................The Greeting Class ..............................................................................Compiling and Running the TestGreeting Program ....................

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Sun Educational Services

Programming Languageht 2007 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision G.1

Compile-Time Errors ............................................................................Runtime Errors ......................................................................................Java Technology Runtime Environment ...........................................

Object-Oriented Programming ...........................................Objectives ...............................................................................................Relevance ................................................................................................Software Engineering ...........................................................................The Analysis and Design Phase ..........................................................Abstraction .............................................................................................Classes as Blueprints for Objects ........................................................Declaring Java Technology Classes ....................................................Declaring Attributes .............................................................................Declaring Methods ................................................................................Accessing Object Members ..................................................................Information Hiding ...............................................................................Encapsulation ........................................................................................Declaring Constructors ........................................................................The Default Constructor ......................................................................Source File Layout ................................................................................Software Packages ................................................................................The package Statement ........................................................................The import Statement ..........................................................................Directory Layout and Packages ..........................................................Development .........................................................................................Compiling Using the -d Option .........................................................Terminology Recap ...............................................................................Using the Java Technology API Documentation ..............................Java Technology API Documentation ...............................................

Java™ viCopyrig

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.................................................. 3-5................................................... 3-6.................................................. 3-9................................................ 3-10................................................ 3-11................................................ 3-12................................................ 3-13................................................ 3-14................................................ 3-15................................................ 3-17................................................ 3-19................................................ 3-20................................................ 3-21................................................ 3-22................................................ 3-23................................................ 3-24................................................ 3-25................................................ 3-26................................................ 3-27................................................ 3-32................................................ 3-36

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Identifiers, Keywords, and Types ......................................Objectives ...............................................................................................Relevance ................................................................................................Comments ..............................................................................................Semicolons, Blocks, and White Space ...............................................Identifiers ...............................................................................................Java Programming Language Keywords ..........................................Primitive Types .....................................................................................Logical – boolean .................................................................................Textual – char .......................................................................................Textual – String ...................................................................................Integral – byte, short, int, and long ...............................................Floating Point – float and double ....................................................Variables, Declarations, and Assignments ........................................Java Reference Types ............................................................................Constructing and Initializing Objects ................................................Memory Allocation and Layout ..........................................................Explicit Attribute Initialization ...........................................................Executing the Constructor ...................................................................Assigning a Variable .............................................................................Assigning References ............................................................................Pass-by-Value ........................................................................................The this Reference ...............................................................................Java Programming Language Coding Conventions ........................

Expressions and Flow Control ..........................................Objectives ...............................................................................................Relevance ................................................................................................Variables and Scope ..............................................................................Variable Scope Example .......................................................................

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Variable Initialization ...........................................................................Initialization Before Use Principle ......................................................Operator Precedence ............................................................................Logical Operators ..................................................................................Bitwise Logical Operators ....................................................................Right-Shift Operators >> and >>> .......................................................Left-Shift Operator << ..........................................................................Shift Operator Examples ......................................................................String Concatenation With + ...............................................................Casting ....................................................................................................Promotion and Casting of Expressions .............................................Simple if, else Statements ..............................................................Complex if, else Statements ..........................................................Switch Statements .................................................................................Looping Statements ..............................................................................Special Loop Flow Control ..................................................................The break Statement ............................................................................The continue Statement .....................................................................Using break Statements with Labels .................................................Using continue Statements with Labels ..........................................

Arrays ...................................................................................Objectives ...............................................................................................Relevance ................................................................................................Declaring Arrays ...................................................................................Creating Arrays .....................................................................................Creating Reference Arrays ...................................................................Initializing Arrays .................................................................................Multidimensional Arrays .....................................................................Array Bounds ........................................................................................

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Using the Enhanced for Loop ............................................................Array Resizing .......................................................................................Copying Arrays .....................................................................................

Class Design ........................................................................Objectives ...............................................................................................Relevance ................................................................................................Subclassing .............................................................................................Single Inheritance ..................................................................................Access Control .......................................................................................Overriding Methods .............................................................................Overridden Methods Cannot Be Less Accessible .............................Invoking Overridden Methods ...........................................................Polymorphism .......................................................................................Virtual Method Invocation ..................................................................Heterogeneous Collections ..................................................................Polymorphic Arguments .....................................................................The instanceof Operator ...................................................................Casting Objects ......................................................................................Overloading Methods ..........................................................................Methods Using Variable Arguments .................................................Overloading Constructors ...................................................................Constructors Are Not Inherited ..........................................................Invoking Parent Class Constructors ...................................................Constructing and Initializing Objects: A Slight Reprise ..................Constructor and Initialization Examples ...........................................The Object Class ..................................................................................The equals Method ..............................................................................An equals Example .............................................................................The toString Method .........................................................................

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Wrapper Classes ...................................................................................Autoboxing of Primitive Types ...........................................................

Advanced Class Features ..................................................Objectives ...............................................................................................Relevance ................................................................................................The static Keyword ...........................................................................Class Attributes .....................................................................................Class Methods .......................................................................................Static Initializers ....................................................................................The final Keyword .............................................................................Final Variables .......................................................................................Blank Final Variables ............................................................................Old-Style Enumerated Type Idiom ....................................................The New Enumerated Type ................................................................Advanced Enumerated Types .............................................................Static Imports .........................................................................................Abstract Classes ....................................................................................The Solution ...........................................................................................Interfaces ................................................................................................The Flyer Example ................................................................................Multiple Interface Example .................................................................Uses of Interfaces ..................................................................................

Exceptions and Assertions ................................................Objectives ...............................................................................................Relevance ................................................................................................Exceptions and Assertions ..................................................................Exceptions ..............................................................................................Exception Example ...............................................................................

Java™ xCopyrig

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The try-catch Statement ...................................................................Call Stack Mechanism ..........................................................................The finally Clause .............................................................................Exception Categories ............................................................................Common Exceptions .............................................................................The Handle or Declare Rule ................................................................Method Overriding and Exceptions ...................................................Creating Your Own Exceptions ..........................................................Handling a User-Defined Exception ..................................................Assertions ...............................................................................................Recommended Uses of Assertions .....................................................Internal Invariants .................................................................................Control Flow Invariants .......................................................................Postconditions and Class Invariants .................................................Controlling Runtime Evaluation of Assertions ................................

Collections and Generics Framework ...............................Objectives ...............................................................................................The Collections API ..............................................................................A List Example ....................................................................................The Map Interface ...................................................................................The Map Interface API ...........................................................................A Map Example ......................................................................................Legacy Collection Classes ....................................................................Ordering Collections ............................................................................The Comparable Interface ...................................................................Example of the Comparable Interface ...............................................The Comparator Interface ...................................................................Example of the Comparator Interface ..............................................Generics .................................................................................................

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Generic Set Example ............................................................................Generic Map Example ..........................................................................Generics: Examining Type Parameters ..............................................Wild Card Type Parameters ................................................................The Type-Safety Guarantee .................................................................The Invariance Challenge ....................................................................The Covariance Response ....................................................................Generics: Refactoring Existing Non-Generic Code ..........................Iterators ...................................................................................................Generic Iterator Interfaces ...................................................................The Enhanced for Loop ......................................................................

I/O Fundamentals ................................................................Objectives ...............................................................................................Command-Line Arguments ................................................................System Properties ..................................................................................The Properties Class .........................................................................I/O Stream Fundamentals ...................................................................Fundamental Stream Classes ..............................................................Data Within Streams .............................................................................The InputStream Methods .................................................................The OutputStream Methods ...............................................................The Reader Methods ............................................................................The Writer Methods ............................................................................Node Streams .........................................................................................A Simple Example .................................................................................Buffered Streams ...................................................................................I/O Stream Chaining ...........................................................................Processing Streams ...............................................................................The InputStream Class Hierarchy ....................................................

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The OutputStream Class Hierarchy ..................................................The ObjectInputStream and The ObjectOutputStream ClassesThe SerializeDate Class ...................................................................The DeSerializeDate Class ..............................................................The Reader Class Hierarchy ...............................................................The Writer Class Hierarchy ...............................................................

Console I/O and File I/O ......................................................Objectives ...............................................................................................Console I/O ...........................................................................................Writing to Standard Output ................................................................Reading From Standard Input ............................................................Simple Formatted Output ....................................................................Simple Formatted Input .......................................................................Files and File I/O ..................................................................................Creating a New File Object ...............................................................The File Tests and Utilities ................................................................File Stream I/O ......................................................................................File Input Example ................................................................................Printing a File .........................................................................................File Output Example .............................................................................

Building Java GUIs Using the Swing API .........................Objectives ...............................................................................................What Are the Java Foundation Classes (JFC)? ..................................What Is Swing? ......................................................................................Swing Architecture ...............................................................................Swing Packages .....................................................................................Examining the Composition of a Java Technology GUI .................Swing Containers ..................................................................................

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Top-Level Containers ...........................................................................Swing Components ...............................................................................Swing Component Hierarchy .............................................................Text Components ..................................................................................Swing Component Properties .............................................................Common Component Properties ........................................................Component-Specific Properties ..........................................................Layout Managers ..................................................................................The BorderLayout Manager .............................................................BorderLayout Example .......................................................................The FlowLayout Manager ..................................................................FlowLayout Example ...........................................................................The BoxLayout Manager .....................................................................The CardLayout Manager ...................................................................GridLayout Example ...........................................................................The GridBagLayout Manager ............................................................GUI Construction ..................................................................................Programmatic Construction ................................................................Key Methods ..........................................................................................

Handling GUI-Generated Events ........................................Objectives ...............................................................................................What Is an Event? .................................................................................Delegation Model ..................................................................................A Listener Example ...............................................................................Event Categories ...................................................................................Method Categories and Interfaces ......................................................Complex Example .................................................................................Multiple Listeners .................................................................................Event Adapters ......................................................................................

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Event Handling Using Inner Classes ................................................Event Handling Using Anonymous Classes ....................................

GUI-Based Applications .....................................................Objectives ...............................................................................................Relevance ................................................................................................How to Create a Menu .........................................................................Creating a JMenuBar .............................................................................Creating a JMenu ...................................................................................Creating a JMenuItem ..........................................................................Creating a JCheckBoxMenuItem .........................................................Controlling Visual Aspects ..................................................................

Threads ................................................................................Objectives ...............................................................................................Relevance ................................................................................................Threads ...................................................................................................Creating the Thread ..............................................................................Starting the Thread ...............................................................................Thread Scheduling ................................................................................Thread Scheduling Example ...............................................................Terminating a Thread ...........................................................................Basic Control of Threads ......................................................................The join Method ..................................................................................Other Ways to Create Threads ............................................................Selecting a Way to Create Threads .....................................................Using the synchronized Keyword ...................................................The Object Lock Flag ............................................................................Releasing the Lock Flag ........................................................................Using synchronized – Putting It Together ......................................

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Thread State Diagram With Synchronization ...................................Deadlock .................................................................................................Thread Interaction – wait and notify ..............................................Thread Interaction .................................................................................Thread State Diagram With wait and notify ................................Monitor Model for Synchronization ..................................................The Producer Class ..............................................................................The Consumer Class ..............................................................................The SyncStack Class ............................................................................The pop Method ....................................................................................The push Method ..................................................................................The SyncTest Class ..............................................................................The SyncTest Class ..............................................................................

Networking ...........................................................................Objectives ...............................................................................................Relevance ................................................................................................Networking ............................................................................................Networking With Java Technology ....................................................Java Networking Model .......................................................................Minimal TCP/IP Server .......................................................................Minimal TCP/IP Client ........................................................................

Sun

Java™ Programmi


ng Language

Preface

About This Course

Java™ Preface, slide xvii of xxviiCopyrig

Th d skills to:

hat leverage theuage, such asrphismrom the

ressionsructs

sing exception


Programming Languageht Copyright 2007 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision G.1

Course Goals

is course provides you with knowledge an

• Create Java™ technology applications tobject-oriented features of the Java langencapsulation, inheritance, and polymo

• Execute a Java technology application fcommand-line

• Use Java technology data types and exp• Use Java technology flow control const• Use arrays and other data collections• Implement error-handling techniques u

handling

Java™ Preface, slide xviii of xxviiCopyrig

nterface (GUI)ents: panels,s

nality to read

rotocol/ommunicates



Course Goals

• Create an event-driven graphical user iby using Java technology GUI componbuttons, labels, text fields, and text area

• Implement input/output (I/O) functiofrom and write to data and text files

• Create multithreaded programs• Create a simple Transmission Control P

Internet Protocol (TCP/IP) client that cthrough sockets

Java™ Preface, slide xix of xxviiCopyrig

Th

nguage to the Java



Course Overview

is course describes the following areas:

• The syntax of the Java programming la• Object-oriented concepts as they apply

programming language• GUI programming• Multithreading• Networking


Course Map

The Java Programming Language Basics

More Object-Oriented Programming

Exceptions, Collections, and I/O

Developing Graphical User Interfaces

Advanced Java Programming

Getting StartedObject-Oriented

Programming

Identifiers,

Keywords, and

Types

Arrays

Class DesignAdvanced

Class Features

Collections and

Console I/O and

File I/O

GUI Event

Handling

GUI-Based

Applications

I/O

Threads Networking

Expressions

and Flow Control

Exceptions

and Assertions Generics Framework Fundamentals

Java™ Programming Language About This Course, xx of xxviiCopyright Copyright 2007 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision G.1

Java™ Preface, slide xxi of xxviiCopyrig

overed inlysis and Design

red in SL-110: Language



Topics Not Covered

• Object-oriented analysis and design – COO-226: Object-Oriented Application AnaUsing UML

• General programming concepts – CoveFundamentals of the Java™ Programming

Java™ Preface, slide xxii of xxviiCopyrig

Bef completedSL g Language, orhav

or C++t editorser, such as



How Prepared Are You?

ore attending this course, you should have-110: Fundamentals of the Java™ Programmin

e:

• Created and compiled programs with C• Created and edited text files using a tex• Used a World Wide Web (WWW) brow

Netscape Navigator™

Java™ Preface, slide xxiii of xxviiCopyrig

in this course



Introductions

• Name• Company affiliation• Title, function, and job responsibility• Experience related to topics presented • Reasons for enrolling in this course• Expectations for this course

Java™ Preface, slide xxiv of xxviiCopyrig

?



How to Use the Icons

Additional resources

Discussion

Note

Caution

Visual Aid

!

Java™ Preface, slide xxv of xxviiCopyrig

T ymbols

ands, files,mmingtput.d numbers thating code that is

and command-a real name or

esent variablesudent as part of



ypographical Conventions and S

• Courier is used for the names of commdirectories, programming code, prograconstructs, and on-screen computer ou

• Courier bold is used for characters anyou type, and for each line of programmreferenced in a textual description.

• Courier italics is used for variablesline place holders that are replaced withvalue.

• Courier italics bold is used to reprwhose values are to be entered by the stan activity.

Java™ Preface, slide xxvi of xxviiCopyrig

T ymbols

w words or



ypographical Conventions and S

• Palatino italics is used for book titles, neterms, or words that are emphasized.

Java™ Preface, slide xxvii of xxviiCopyrig

Jav e followingadd

ethods, and

es unless an.rations,e.g System

soft Windows



Additional Conventions

a programming language examples use thitional conventions:

• Courier is used for the class names, mkeywords.

• Methods are not followed by parenthesformal or actual parameter list is show

• Line breaks occur where there are sepaconjunctions, or white space in the cod

• If a command on the Solaris™ Operatin(Solaris OS) is different from the Microplatform, both commands are shown.

Sun

Java™ Programmi


ng Language

Module 1

Getting Started

Java™ Module 1, slide 2 of 23Copyrig

ologyechnology

l Machine

a platform that

ne” and “JVM”platform.



Objectives

• Describe the key features of Java techn• Write, compile, and run a simple Java t

application• Describe the function of the Java Virtua

(JVM™)• Define garbage collection• List the three tasks performed by the Jav

handle code security

NOTE: The terms “Java Virtual Machimean a Virtual Machine for the Java™


mplete programs for

g language? improve on



Relevance

• Is the Java programming language a colanguage or is it useful only for writingthe Web?

• Why do you need another programmin• How does the Java technology platform

other language platforms?


gy?

d applications.



What Is the Java™ Technolo

• Java technology is:• A programming language• A development environment• An application environment• A deployment environment

• It is similar in syntax to C++.• It is used for developing both applets an


ology

uages

and clear coder:



Primary Goals of the Java Techn

• Provides an easy-to-use language by:• Avoiding many pitfalls of other lang• Being object-oriented• Enabling users to create streamlined

• Provides an interpreted environment fo• Improved speed of development• Code portability


ology

ead of activitye time they are

ally duringate sources




• Enables users to run more than one thr• Loads classes dynamically; that is, at th

actually needed• Supports changing programs dynamic

runtime by loading classes from dispar• Furnishes better security


ology

Th

1.




e following features fulfill these goals:

• The Java Virtual Machine (JVM™)1

• Garbage collection• The Java Runtime Environment (JRE)• JVM tool interface

The terms "Java Virtual Machine" and "JVM" mean a Virtual Machine for the Java platform


ons

revelopment tool



The Java Virtual Machine

• Provides hardware platform specificati• Reads compiled byte codes that are

platform-independent• Is implemented as software or hardwa• Is implemented in a Java technology de

or a Web browser


JVM

[CPU])




provides definitions for the:

• Instruction set (central processing unit • Register set• Class file format• Stack• Garbage-collected heap• Memory area• Fatal error reporting• High-precision timing support


hen the code is

y Suncompliant class

environments.




• The majority of type checking is done wcompiled.

• Implementation of the JVM approved bMicrosystems must be able to run any file.

• The JVM executes on multiple operating


ded should be

rogrammer’s

des alocation.aracteristics:ger needed

plementations



Garbage Collection

• Allocated memory that is no longer needeallocated.

• In other languages, deallocation is the presponsibility.

• The Java programming language provisystem-level thread to track memory al

• Garbage collection has the following ch• Checks for and frees memory no lon• Is done automatically• Can vary dramatically across JVM im


ent

Th s follows:

ser

deer

ter

e

are

e



The Java Runtime Environm

e Java application environment performs aCompile

TestGreeting.java

TestGreeting.class

Load from

Clasload

Bytecoverifi

Interpre

Runtim

Hardw

Runtim

javac

java

hard disk,network,or othersource


O In-Time

e

codeenerator

JIT



peration of the JRE With a Just-(JIT) Compiler

Compile

TestGreeting.java

TestGreeting.class

Classloader

Bytecodeverifier

Interpreter

Runtime

Hardwar

Runtime

javac

java

g

Load fromhard disk,network,or othersource


Th



JVM™ Tasks

e JVM performs three main tasks:

• Loads code• Verifies code• Executes code


ution of a

in separate



The Class Loader

• Loads all classes necessary for the execprogram

• Maintains classes of the local file systemnamespaces

• Prevents spoofing


En

ion.rity.flows or

code are

sion of integers



The Bytecode Verifier

sures that:

• The code adheres to the JVM specificat• The code does not violate system integ• The code causes no operand stack over

underflows.• The parameter types for all operational

correct.• No illegal data conversions (the conver

to pointers) have occurred.


Th

123456789

Th

12345



A Simple Java Application

e TestGreeting.java Application

//// Sample "Hello World" application//public class TestGreeting{public static void main (String[] args) {

Greeting hello = new Greeting(); hello.greet(); }}

e Greeting.java Class

public class Greeting {public void greet() {

System.out.println(“hi”); }}


ion



The TestGreetingApplicat

• Comment lines• Class declaration• The main method• Method body




The GreetingClass

• Class declaration• The greet method


C reeting

atically.ing command:

rrors.



ompiling and Running the TestGProgram

• Compile TestGreeting.java:javac TestGreeting.java

• The Greeting.java is compiled autom• Run the application by using the follow

java TestGreeting

• Locate common compile and runtime e


symbolang.String)ream

estGreetingd



Compile-Time Errors

• javac: Command not found

• Greeting.java:4: cannot resolvesymbol : method printl (java.llocation: class java.io.PrintStSystem.out.printl("hi");

^

• TestGreet.java:4: Public class Tmust be defined in a file calle"TestGreeting.java".


in



Runtime Errors

• Can’t find class TestGreeting

• Exception in thread "main"java.lang.NoSuchMethodError: ma


nment



Java Technology Runtime Enviro

Com

pile

TestGreeting.java

TestGreeting.class

Run

time

Greeting.class

Greeting.java

JVM

UNIX® DOS JavaOS™

JVMJVM

javac

java

Also compiles

Also loads

Can run on multiple platforms

Sun

Java™ Programmi

ming


ng Language

Module 2

Object-Oriented Program


ncapsulation,

ogy application

onstructor, and

public assulation

ogramming



Objectives

• Define modeling concepts: abstraction, eand packages

• Discuss why you can reuse Java technolcode

• Define class, member, attribute, method, cpackage

• Use the access modifiers private andappropriate for the guidelines of encap

• Invoke a method on a particular object• Use the Java technology application pr

interface (API) online documentation


e analysis and

and code reuse?ing language

language?



Relevance

• What is your understanding of softwardesign?

• What is your understanding of design• What features does the Java programm

possess that make it an object-oriented• Define the term object-oriented.


0s–Up)

oft Windows

penLook

JDBC™

Java



Software Engineering

Machine Code (Late 1940s–Up)

High-Level Languages (1950s–Up) Operating Systems (196

Libraries / Functional APIs (1960s–Early 1980s)

Object-Oriented Languages (1980s–Up)

Toolkits / Frameworks / Object APIs (1990s–Up)

Fortran LISP C UNIX MicrosMacOS

NASTRAN X-Windows

COBOL

TCP/IP ISAM O

SELF Smalltalk Common Lisp Object System Eiffel

AWT / J.F.C./Swing Jini™ JavaBeans™Java 2 SDK

C++

OS/360


se

ds to do:tors and

t:ractionsstemimplify the



The Analysis and Design Pha

• Analysis describes what the system neeModeling the real-world, including acactivities, objects, and behaviors

• Design describes how the system does i• Modeling the relationships and inte

between objects and actors in the sy• Finding useful abstractions to help s

problem or solution


e used in many

tes and

of objects thats can be usedbehavior



Abstraction

• Functions – Write an algorithm once to bsituations

• Objects – Group a related set of attribubehaviors into a class

• Frameworks and APIs – Large groups support a complex activity; Frameworkas is or be modified to extend the basic


ects

s a device fromructed.n object:object includes.each object

e key features:



Classes as Blueprints for Obj

• In manufacturing, a blueprint describewhich many physical devices are const

• In software, a class is a description of a• A class describes the data that each • A class describes the behaviors that

exhibits.• In Java technology, classes support thre

of object-oriented programming (OOP)• Encapsulation• Inheritance• Polymorphism


sses



Declaring Java Technology Cla

• Basic syntax of a Java class:<modifier>* class <class_name> {

<attribute_declaration>*<constructor_declaration>*<method_declaration>*

}

• Example:1 public class Vehicle {2 private double maxLoad;3 public void setMaxLoad(double value) {4 maxLoad = value;5 }6 }


e>];



Declaring Attributes

• Basic syntax of an attribute:<modifier>* <type> <name> [ = <initial_valu

• Examples:1 public class Foo {2 private int x;3 private float y = 10000.0F;4 private String name = "Bates Motel";5 }


t>* ) {



Declaring Methods

• Basic syntax of a method:<modifier>* <return_type> <name> ( <argumen

<statement>*}

• Examples:1 public class Dog {2 private int weight;3 public int getWeight() {4 return weight;5 }6 public void setWeight(int newWeight) {7 if ( newWeight > 0 ) {8 weight = newWeight;9 }10 }11 }


s

r>

ncluding

s public



Accessing Object Member

• The dot notation is: <object>.<membe• This is used to access object members, i

attributes and methods.• Examples of dot notation are:

d.setWeight(42);d.weight = 42; // only permissible if weight i


Th

+

+

+

t access to to a MyDate

ound



Information Hiding

e problem:

MyDate

day : int

month : int

year : int

Client code has direcinternal data (d refersobject):

d.day = 32;// invalid day

d.month = 2; d.day = 30;// plausible but wrong

d.day = d.day + 1;// no check for wrap ar


Th setters andnal data:

false

e if wrap around

+

+

+

+

+

+

-d

-m

-y



Information Hiding

e solution:Client code must usegetters to access inter

MyDate d = new MyDate();

d.setDay(32);// invalid day, returns

d.setMonth(2);d.setDay(30);// plausible but wrong,// setDay returns false

d.setDay(d.getDay() + 1);// this will return fals// needs to occur

setDay(int) : boolean

setYear(int) : boolean

setMonth(int) : boolean

getDay() : int

getMonth() : int

getYear() : int

MyDate

ay : int

onth : int

ear : int

Verify days in month


lasscess data



Encapsulation

• Hides the implementation details of a c• Forces the user to use an interface to ac• Makes the code more maintainable

+setDay(int) : boolean

+setYear(int) : boolean

+setMonth(int) : boolean

+getDay() : int

+getMonth() : int

+getYear() : int

MyDate

-date : long

-isDayValid(int) : boolean




Declaring Constructors

• Basic syntax of a constructor:[<modifier>] <class_name> ( <argument>* ) {<statement>*

}

• Example:1 public class Dog {23 private int weight;45 public Dog() {6 weight = 42;7 }8 }


in every class.ructors, thecally:umentstyinstances withnstructor.



The Default Constructor

• There is always at least one constructor• If the writer does not supply any const

default constructor is present automati• The default constructor takes no arg• The default constructor body is emp

• The default enables you to create objectnew Xxx()without having to write a co


ort.java file

{...}



Source File Layout

• Basic syntax of a Java source file is:[<package_declaration>]<import_declaration>*<class_declaration>+

• For example, the VehicleCapacityRepis:1 package shipping.reports;23 import shipping.domain.*;4 import java.util.List;5 import java.io.*;67 public class VehicleCapacityReport {8 private List vehicles;9 public void generateReport(Writer output)10 }


ystems.ackages.

icle

RiverBarge



Software Packages

• Packages help manage large software s• Packages can contain classes and sub-p

Veh

Truck

Company Owns 0..*

shipping

domaingui

reports


is:

eginning of the

ce file. is placed into

d separated by



The packageStatement

• Basic syntax of the package statement package <top_pkg_name>[.<sub_pkg_name>]*;

• Examples of the statement are:package shipping.gui.reportscreens;

• Specify the package declaration at the bsource file.

• Only one package declaration per sour• If no package is declared, then the class

the default package.• Package names must be hierarchical an

dots.


:name>;

g:

ses



The importStatement

• Basic syntax of the import statement isimport <pkg_name>[.<sub_pkg_name>]*.<class_ORimport <pkg_name>[.<sub_pkg_name>]*.*;

• Examples of the statement are:import java.util.List;import java.io.*;import shipping.gui.reportscreens.*;

• The import statement does the followin• Precedes all class declarations• Tells the compiler where to find clas


es

containing the

packages.

.class



Directory Layout and Packag

• Packages are stored in the directory treepackage name.

• An example is the shipping applicationshipping/

domain/

gui/

reports/

Vehicle.classRiverBarge.classTruck.class

VehicleCapacityReport

Company.class


J



DevelopmentavaProjects/

ShippingPrj/

src/

docs/

shipping/

domain/gui/reports/

classes/

shipping/

domain/gui/reports/


on



Compiling Using the -dOpti

cd JavaProjects/ShippingPrj/srcjavac -d ../classes shipping/domain/*.java


run-time object

;iable, and data

bject;roceduresed to initialize

b-packages



Terminology Recap

• Class – The source-code blueprint for a• Object – An instance of a class;

also known as instance• Attribute – A data element of an object

also known as data member, instance varfield

• Method – A behavioral element of an oalso known as algorithm, function, and p

• Constructor – A method-like construct ua new object

• Package – A grouping of classes and su


PI

HTML) files

s hyperlinks tot package.rarchy, avariables, a list



Using the Java Technology ADocumentation

• A set of Hypertext Markup Language (provides information about the API.

• A frame describes a package and containinformation describing each class in tha

• A class document includes the class hiedescription of the class, a list of memberof constructors, and so on.


Java Technology APIDocumentation

Java™ Programming Language Module 2, slide 26 of 26Copyright Copyright 2007 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision G.1

Sun

Java™ Programmi

Id Types


ng Language

Module 3

entifiers, Keywords, and


identifiers

xtual typeseference variable



Objectives

• Use comments in a source program• Distinguish between valid and invalid • Recognize Java technology keywords• List the eight primitive types• Define literal values for numeric and te• Define the terms primitive variable and r


variableiables of class



Objectives

• Declare variables of class type• Construct an object using new• Describe default initialization• Describe the significance of a reference• State the consequences of assigning var

type


n variableswith object



Relevance

• Do you know the primitive Java types?• Can you describe the difference betwee

holding primitive values as compared references?


Th ava technologypro

// c

/* c* o*/

/** * */



Comments

e three permissible styles of comment in a Jgram are:

omment on one line

omment on oner more lines

documentation commentcan also span one or more lines


Space

terminated by

nd by opening



Semicolons, Blocks, and White

• A statement is one or more lines of codea semicolon (;):totals = a + b + c

+ d + e + f;

• A block is a collection of statements bouand closing braces:{ x = y + 1; y = x + 1;}


Space




• A class definition uses a special block:public class MyDate { private int day; private int month; private int year;}

• You can nest block statements.while ( i < large ) {a = a + i;// nested blockif ( a == max ) {b = b + a;a = 0;

}i = i + 1;

}


Space

in a Java




• Any amount of white space is permittedprogram.For example:{int x;x=23*54;}

is equivalent to:{int x;

x = 23 * 54;}


Ide

methodcore (_), or

m length



Identifiers

ntifiers have the following characteristics:

• Are names given to a variable, class, or• Can start with a Unicode letter, unders

dollar sign ($)• Are case-sensitive and have no maximu• Examples:

identifieruserNameuser_name_sys_var1$change


ywords

Re e

abs switch

ass synchronized

boo this

bre d throw

byt throws

cas transient

cat try

cha void

cla volatile

con while



Java Programming Language Ke

served literal words: null, true, and fals

tract continue for new

ert default goto package

lean do if private

ak double implements protecte

e else import public

e enum instanceof return

ch extends int short

r final interface static

ss finally long strictfp

st float native super


Th t primitivetyp



Primitive Types

e Java programming language defines eighes:

• Logical – boolean• Textual – char• Integral – byte, short, int, and long

• Floating – double and float


Th acteristics:

, true and

type and assigns



Logical – boolean

e boolean primitive has the following char

• The boolean data type has two literalsfalse.

• For example, the statement:boolean truth = true;

declares the variable truth as booleanit a value of true.


Th characteristics:

quotes (’ ’)

is replaced with

letter phi [Φ].



Textual – char

e textual char primitive has the following

• Represents a 16-bit Unicode character• Must have its literal enclosed in single • Uses the following notations:

'a' The letter a

'\t' The tab character

'\u????' A specific Unicode character, ????, exactly four hexadecimal digits .For example, ’\u03A6’ is the Greek


Th aracteristics:

s (" ")



Textual – String

e textual String type has the following ch

• Is not a primitive data type; it is a class• Has its literal enclosed in double quote

"The quick brown fox jumps over the lazy dog."

• Can be used as follows:String greeting = "Good Morning !! \n";String errorMessage = "Record Not Found !";


long

Th aracteristics:

mal, octal, or

ng.

e.

al value.



Integral – byte, short, int, and

e integral primitives have the following ch

• Integral primates use three forms: Decihexadecimal

• Literals have a default type of int.

• Literals with the suffix L or l are of type lo

2 The decimal form for the integer 2.

077 The leading 0 indicates an octal valu

0xBAAC The leading 0x indicates a hexadecim


long

ranges:



Integral – byte, short, int, and

• Integral data types have the following

Integer Length Name or Type Range

8 bits byte -27 to 27-1

16 bits short -215 to 215 -1

32 bits int -231 to 231 -1

64 bits long -263 to 263 -1


uble

Th ngcha

ecimal point or

ouble)

dant D



Floating Point – floatand do

e floating point primitives have the followiracteristics:

• Floating-point literal includes either a done of the following:• E or e (add exponential value)• F or f (float)• D or d (double)

3.14 A simple floating-point value (a d

6.02E23 A large floating-point value

2.718F A simple float size value

123.4E+306D A large double value with redun


uble

owing sizes:



Floating Point – floatand do

• Literals have a default type of double.• Floating-point data types have the foll

Float Length Name or Type

32 bits float

64 bits double


Variables, Declarations, andAssignments

1 public class Assign {2 public static void main (String args []) {3 // declare integer variables4 int x, y;5 // declare and assign floating point6 float z = 3.414f;7 // declare and assign double8 double w = 3.1415;9 // declare and assign boolean10 boolean truth = true;11 // declare character variable12 char c;13 // declare String variable14 String str;15 // declare and assign String variable16 String str1 = "bye";17 // assign value to char variable18 c = 'A';19 // assign value to String variable20 str = "Hi out there!";21 // assign values to int variables22 x = 6;23 y = 1000;24 }25 }



pes all others

n object.

r) { ... }



Java Reference Types

• In Java technology, beyond primitive tyare reference types.

• A reference variable contains a handle to a• For example:

1 public class MyDate {2 private int day = 1;3 private int month = 1;4 private int year = 2000;5 public MyDate(int day, int month, int yea6 public String toString() { ... }7 }

1 public class TestMyDate {2 public static void main(String[] args) {3 MyDate today = new MyDate(22, 7, 1964);4 }5 }


jects

ing actions:

rformed.

the new

o a variable.



Constructing and Initializing Ob

• Calling new Xyz() performs the followa. Memory is allocated for the object.b. Explicit attribute initialization is pec. A constructor is executed.d. The object reference is returned by

operator.• The reference to the object is assigned t• An example is:

MyDate my_birth = new MyDate(22, 7, 1964);


ut

a reference:

for MyDate:



Memory Allocation and Layo

• A declaration allocates storage only forMyDate my_birth = new MyDate(22, 7, 1964);

• Use the new operator to allocate space MyDate my_birth = new MyDate(22, 7, 1964);

my_birth ????

my_birth ????

day

month

year

0

0

0


n

ttribute



Explicit Attribute Initializatio

• Initialize the attributes as follows:MyDate my_birth = new MyDate(22, 7, 1964);

• The default values are taken from the adeclaration in the class.

my_birth ????

day

month

year

1

1

2000


llows:

r, the first



Executing the Constructor

• Execute the matching constructor as foMyDate my_birth = new MyDate(22, 7, 1964);

• In the case of an overloaded constructoconstructor can call another.

my_birth ????

day

month

year

22

7

1964


eference



Assigning a Variable

• Assign the newly created object to the rvariable as follows:MyDate my_birth = new MyDate(22, 7, 1964);

my_birth 0x01abcdef

day

month

year

22

7

1964


nt to two



Assigning References

• Two variables refer to a single object:1 int x = 7;2 int y = x;3 MyDate s = new MyDate(22, 7, 1964);4 MyDate t = s;

• Reassignment makes two variables poiobjects:5 t = new MyDate(22, 12, 1964);

x 7

y 7

s 0x01234567

t 0x01234567

22 7 1964

x 7

y 7

s 0x01234567

t 0x12345678

22 7 1964

22 12 1964


ogramminglue. argument to areference to the

d in the callede is never



Pass-by-Value

• In a single virtual machine, the Java prlanguage only passes arguments by va

• When an object instance is passed as anmethod, the value of the argument is aobject.

• The contents of the object can be changemethod, but the original object referencchanged.


123456789101112



Pass-by-Value

public class PassTest {

// Methods to change the current values public static void changeInt(int value) { value = 55; } public static void changeObjectRef(MyDate ref) { ref = new MyDate(1, 1, 2000); } public static void changeObjectAttr(MyDate ref){ ref.setDay(4); }


1314151617181920212223

Th



Pass-by-Value

public static void main(String args[]) { MyDate date; int val;

// Assign the int val = 11; // Try to change it changeInt(val); // What is the current value? System.out.println("Int value is: " + val);

e result of this output is:

Int value is: 11


24252627282930

Th



Pass-by-Value

// Assign the date date = new MyDate(22, 7, 1964); // Try to change it changeObjectRef(date); // What is the current value?

System.out.println("MyDate: " + date);


MyDate: 22-7-1964


3132333435363738

Th



Pass-by-Value

// Now change the day attribute // through the object reference changeObjectAttr(date); // What is the current value?

System.out.println("MyDate: " + date);}

}


MyDate: 4-7-1964


He

variables and

er to another



The thisReference

re are a few uses of the this keyword:

• To resolve ambiguity between instanceparameters

• To pass the current object as a parametmethod or constructor


123456789101112131415



The thisReference

public class MyDate { private int day = 1; private int month = 1; private int year = 2000;

public MyDate(int day, int month, int year) { this.day = day; this.month = month; this.year = year; } public MyDate(MyDate date) { this.day = date.day; this.month = date.month; this.year = date.year; }


1617181920212223242526



The thisReference

public MyDate addDays(int moreDays) { MyDate newDate = new MyDate(this); newDate.day = newDate.day + moreDays; // Not Yet Implemented: wrap around code... return newDate; }public String toString() {

return "" + day + "-" + month + "-" + year; }}


12345678



The thisReference

public class TestMyDate { public static void main(String[] args) { MyDate my_birth = new MyDate(22, 7, 1964); MyDate the_next_week = my_birth.addDays(7);

System.out.println(the_next_week); }}


oding



Java Programming Language CConventions

• Packages:com.example.domain;

• Classes, interfaces, and enum types:SavingsAccount

• Methods:getAccount()

• Variables:currentCustomer

• Constants:HEAD_COUNT


oding

on.

ss members.



Java Programming Language CConventions

• Control structures:if ( condition ) {statement1;

} else {statement2;

}

• Spacing:• Use one statement per line.• Use two or four spaces for indentati

• Comments:• Use // to comment inline code.• Use /** documentation */ for cla

Sun

Java™ Programmi

ontrol


ng Language

Module 4

Expressions and Flow C


variablesablesence before

are operatorsssignments of



Objectives

• Distinguish between instance and local• Describe how to initialize instance vari• Identify and correct a Possible refer

assignment compiler error• Recognize, describe, and use Java softw• Distinguish between legal and illegal a

primitive types


requirements

d required casts

structions andnue as flow



Objectives

• Identify boolean expressions and theirin control constructs

• Recognize assignment compatibility anin fundamental types

• Use if, switch, for, while, and do conthe labelled forms of break and conticontrol structures in a program


ogrammers?th the same

ed in otherguages use to



Relevance

• What types of variables are useful to pr• Can multiple classes have variables wi

name and, if so, what is their scope?• What types of control structures are us

languages? What methods do these lancontrol flow?


Lo

od and arek variableshod is executedd

Va :

ation.atically.



Variables and Scope

cal variables are:

• Variables that are defined inside a methcalled local, automatic, temporary, or stac

• Variables that are created when the metare destroyed when the method is exite

riable initialization comprises the following

• Local variables require explicit initializ• Instance variables are initialized autom


pub p

p

} p

}}

pubp

}}

Heap Memory

ScopeExample

i 1

ck



Variable Scope Examplelic class ScopeExample {rivate int i=1;

ublic void firstMethod() { int i=4, j=5;

this.i = i + j; secondMethod(7);

ublic void secondMethod(int i) {int j=8; this.i = i + j;

lic class TestScoping {ublic static void main(String[] args) {ScopeExample scope = new ScopeExample();

scope.firstMethod();

main

firstMethod

i

j

secondMethod

i

j

this

this

scope

4

5

7

8

Execution Sta




Variable Initialization

Variable Value

byte 0

short 0

int 0

long 0L

float 0.0F

double 0.0D

char '\u0000'

boolean false

All reference types null


iple

Th ave beenini

javaTest en initialized 1 er

345678910 ation11



Initialization Before Use Princ

e compiler will verify that local variables htialized before used.

c TestInitBeforeUse.javaInitBeforeUse.java:10: variable y might not have bez = y + x; // Possible use before initialization ^ror

public void doComputation() { int x = (int)(Math.random() * 100); int y; int z; if (x > 50) { y = 9; } z = y + x; // Possible use before initializ }


Op ssociative++ to L* to R+ to R<< to R< to R== to R& to R^ to R| to R&& to R|| to R<b to L= * to L



Operator Precedence

erators A-- + unary - unary ~ ! (<data_type>) R/ % L- L>> >>> L> <= >= instanceof L!= L

LLLLL

oolean_expr> ? <expr1> : <expr2> R= /= %= += -= <<= >>= >>>= &= ^= |= R


e:

:



Logical Operators

• The boolean operators are:! – NOT & – AND| – OR ^ – XOR

• The short-circuit boolean operators ar&& – AND || – OR

• You can use these operators as followsMyDate d = reservation.getDepartureDate();if ( (d != null) && (d.day > 31) {// do something with d

}


0 1

1 1

0 1

0 1

1 1

1 1



Bitwise Logical Operators

• The integer bitwise operators are:~ – Complement & – AND^ – XOR | – OR

• Byte-sized examples include:

0 0 01 1 1 1 1

1 1 10 0 0 0 0

~

0 0 01 1 1

0 0 01 1 1

0 0 0 0 1 1

&

0 0 01 1 1

0 0 01 1 1|

0 01 1 1 1

0 0 0 01 1 1 1

0 0 01 1 1 1 1

0 0 0 00 11 1

^


>>>

rator:

ft.rator:. shift.



Right-Shift Operators >>and

• Arithmetic or signed right shift (>>) ope• Examples are:

128 >> 1 returns 128/21 = 64256 >> 4 returns 256/24 = 16-256 >> 4 returns -256/24 = -16

• The sign bit is copied during the shi• Logical or unsigned right-shift (>>>) ope

• This operator is used for bit patterns• The sign bit is not copied during the


s:



Left-Shift Operator <<

• Left-shift (<<) operator works as follow128 << 1 returns 128 * 21 = 25616 << 2 returns 16 * 22 = 64


0 10 0 1 1

1 1

0

00

11

1111

0

00

13

-13

135

-135

13

-13

1111 00011 1

1 1001

0 0111 0000 0

10 1 10

0 0111 0000 0

1111 00011 1

0 00 0 0

0 00 0 0



Shift Operator Examples

1

1

0

0

00 0 000 0 000 0 000 0 0

11 1 1 11 1 111 1 1 11 1 1 11 1 1

00 0 01357 =

-1357 =

57 >> 5 =

57 >> 5 =

7 >>> 5 =

7 >>> 5 =

57 << 5 =

57 << 5 =

11 1 1 111 1 1 11 1 1 11 1 1

1111 00011 1 1 11 1 111 1 11 1 1

000 0 000 0 000 0 000 0 0

0 0111 0000 0 000 0 000 0 000 0

0 00 0 0

11 1 11

000 0 000 0 000 0 000 0 00 00 0 0

11 1 1 111 1 1 11 1 1 11 1 10 00 0 0


+

.bjects



String Concatenation With

• The + operator works as follows:• Performs String concatenation• Produces a new String:

String salutation = "Dr.";String name = "Pete" + " " + "Seymour";String title = salutation + " " + name;

• One argument must be a String object• Non-strings are converted to String o

automatically.


nment, theent with a cast. requires an

a cast

a cast

ger literal



Casting

• If information might be lost in an assigprogrammer must confirm the assignm

• The assignment between long and intexplicit cast.long bigValue = 99L;int squashed = bigValue; // Wrong, needsint squashed = (int) bigValue; // OK

int squashed = 99L; // Wrong, needsint squashed = (int) 99L; // OK, but...int squashed = 99; // default inte


ssions

o a longer form

e variable type bits) as the

l

egal



Promotion and Casting of Expre

• Variables are promoted automatically t(such as int to long).

• Expression is assignment-compatible if this at least as large (the same number ofexpression type.long bigval = 6; // 6 is an int type, OKint smallval = 99L; // 99L is a long, illega

double z = 12.414F; // 12.414F is float, OKfloat z1 = 12.414; // 12.414 is double, ill


ts

Th

if <

Ex

if (Sy

or

if (Sy

}



Simple if, elseStatemen

e if statement syntax:

( <boolean_expression> )statement_or_block>

ample:

x < 10 )stem.out.println("Are you finished yet?");

(recommended):

x < 10 ) {stem.out.println("Are you finished yet?");


nts

Th

if <

els<

Ex

if (Sy

} elSy

}



Complex if, elseStateme

e if-else statement syntax:

( <boolean_expression> )statement_or_block>estatement_or_block>

ample:

x < 10 ) {stem.out.println("Are you finished yet?");se {stem.out.println("Keep working...");


nts

Th

if <

els<

Ex

int sif (Sy ;

} elSy

} elSy

}



Complex if, elseStateme

e if-else-if statement syntax:

( <boolean_expression> )statement_or_block>e if ( <boolean_expression> )statement_or_block>

ample:

count = getCount(); // a method defined in the clascount < 0) {stem.out.println("Error: count value is negative.")se if (count > getMaxCount()) {stem.out.println("Error: count value is too big.");se {stem.out.println("There will be " + count +

" people for lunch today.");


Th

swic

c

d

}



Switch Statements

e switch statement syntax:

tch ( <expression> ) {ase <constant1>:<statement_or_block>*[break;]

ase <constant2>:<statement_or_block>*[break;]

efault:<statement_or_block>*[break;]


A s

switca

ca

de

}



Switch Statements

witch statement example:

ch ( carModel ) {se DELUXE:addAirConditioning();addRadio();addWheels();addEngine();break;se STANDARD:addRadio();addWheels();addEngine();break;fault:addWheels();addEngine();


Th vious example:

switca

ca

de

}

Wi falls througheac



Switch Statements

is switch statement is equivalent to the pre

ch ( carModel ) {se DELUXE:addAirConditioning();se STANDARD:addRadio();fault:addWheels();addEngine();

thout the break statements, the execution h subsequent case clause.


Th

for<

Ex

for Sy

or

for Sy

}



Looping Statements

e for loop:

( <init_expr>; <test_expr>; <alter_expr> )statement_or_block>

ample:

( int i = 0; i < 10; i++ )stem.out.println(i + " squared is " + (i*i));

(recommended):

( int i = 0; i < 10; i++ ) {stem.out.println(i + " squared is " + (i*i));


Th

whi<

Ex

int whilSyi+

}



Looping Statements

e while loop:

le ( <test_expr> )statement_or_block>

ample:

i = 0;e ( i < 10 ) {stem.out.println(i + " squared is " + (i*i));+;


Th

do<

whi

Ex

intdo {Syi+

} wh



Looping Statements

e do/while loop:

statement_or_block>le ( <test_expr> );

ample:

i = 0;

stem.out.println(i + " squared is " + (i*i));+;ile ( i < 10 );


l

dand, where



Special Loop Flow Contro

• The break [<label>]; command• The continue [<label>]; comman• The <label> : <statement> comm

<statement> should be a loop


1234567



The breakStatement

do {statement;if ( condition ) {break;

}statement;

} while ( test_expr );


1234567



The continueStatement

do {statement;if ( condition ) {continue;

}statement;



abels

123456789101112



Using breakStatements with L

outer:do {statement1;do {statement2;if ( condition ) {break outer;

}statement3;

} while ( test_expr );statement4;



U Labels

123456789101112



sing continueStatements with

test:do {statement1;do {statement2;if ( condition ) {continue test;

}statement3;

} while ( test_expr );statement4;


Sun

Java™ Programmi


ng Language

Module 5

Arrays


class, or array

nitializedf an arrayn array

ne array to



Objectives

• Declare and create arrays of primitive, types

• Explain why elements of an array are i• Explain how to initialize the elements o• Determine the number of elements in a• Create a multidimensional array• Write code to copy array values from o

another


Wh



Relevance

at is the purpose of an array?


es:

new.



Declaring Arrays

• Group data objects of the same type.• Declare arrays of primitive or class typ

char s[];Point p[];

char[] s;Point[] p;

• Create space for a reference.• An array is an object; it is created with


Us .

For

12345678910



Creating Arrays

e the new keyword to create an array object

example, a primitive (char) array:

public char[] createArray() {char[] s;

s = new char[26];for ( int i=0; i<26; i++ ) {s[i] = (char) (’A’ + i);

}

return s;}


C imitives

ory



reating an Array of Character Pr

main

createArray s

this

char[]

A

Execution Stack

Heap Mem

B

C

D

Z


An

12345678910



Creating Reference Arrays

other example, an object array:

public Point[] createArray() {Point[] p;

p = new Point[10];for ( int i=0; i<10; i++ ) {p[i] = new Point(i, i+1);

}

return p;}


C imitives

nt

0

1

Point

x

y

1

2

int

2

3



reating an Array of Character PrWith PointObjects

main

createArray p

this

Point[]

Execution Stack

Heap Memory

Poi

x

y

Po

x

y


Strnamnamnamnam

{

MyDdatdatdatdat

{, 7, 1964), 1, 2000),, 12, 1964)



Initializing Arrays

• Initialize an array element.• Create an array with initial values.ing[] names;es = new String[3];es[0] = "Georgianna";es[1] = "Jen";es[2] = "Simon";

String[] names = "Georgianna","Jen","Simon"

};

ate[] dates;es = new MyDate[3];es[0] = new MyDate(22, 7, 1964);es[1] = new MyDate(1, 1, 2000);es[2] = new MyDate(22, 12, 1964);

MyDate[] dates = new MyDate(22new MyDate(1,new MyDate(22

};


Ar

int[twoDtwoD

int[



Multidimensional Arrays

rays of arrays:

][] twoDim = new int[4][];im[0] = new int[5];im[1] = new int[5];

][] twoDim = new int[][4]; // illegal


h:



Multidimensional Arrays

• Non-rectangular arrays of arrays:twoDim[0] = new int[2];twoDim[1] = new int[4];twoDim[2] = new int[6];twoDim[3] = new int[8];

• Array of four arrays of five integers eacint[][] twoDim = new int[4][5];


All

publfo

}}



Array Bounds

array subscripts begin at 0:

ic void printElements(int[] list) {r (int i = 0; i < list.length; i++) {System.out.println(list[i]);


op

Jav rsion 5.0int over arrays:

publfo

}}

Th in list do.



Using the Enhanced forLo

a 2 Platform, Standard Edition (J2SE™) veroduced an enhanced for loop for iterating

ic void printElements(int[] list) {r ( int element : list ) {System.out.println(element);

e for loop can be read as for each element


e to refer to an



Array Resizing

• You cannot resize an array.• You can use the same reference variabl

entirely new array, such as:int[] myArray = new int[6];myArray = new int[10];


Th rays is:

123456789 h);



Copying Arrays

e System.arraycopy() method to copy ar

//original arrayint[] myArray = { 1, 2, 3, 4, 5, 6 };

// new larger arrayint[] hold = { 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 };

// copy all of the myArray array to the hold// array, starting with the 0th indexSystem.arraycopy(myArray, 0, hold, 0, myArray.lengt

Sun

Java™ Programmi


ng Language

Module 6

Class Design


ding, overriding,

nd the default

d method

on and



Objectives

• Define inheritance, polymorphism, overloaand virtual method invocation

• Use the access modifiers protected a(package-friendly)

• Describe the concepts of constructor anoverloading

• Describe the complete object constructiinitialization operation


Ho pport objectinh



Relevance

w does the Java programming language sueritance?


Th

";

ls() {...}



Subclassing

e Employee class is shown here.

public class Employee { public String name = " public double salary; public Date birthDate;

public String getDetai}

Employee

+name : String = ""

+salary : double

+birthDate : Date

+getDetails() : String


Th

";

nt;

ls() {...}



Subclassing

e Manager class is shown here.

public class Manager { public String name = " public double salary; public Date birthDate; public String departme


Manager

+name : String = ""

+salary : double

+birthDate : Date

+department : String



C Manager

";

ls() {...}

ends Employee {nt;



lass Diagrams for EmployeeandUsing Inheritance

public class Employee { public String name = " public double salary; public Date birthDate;


public class Manager ext public String departme}

Manager

+department : String

Employee

+name : String = ""

+salary : double

+birthDate : Date



ss, it is called

le inheritance

s>] {



Single Inheritance

• When a class inherits from only one clasingle inheritance.

• Interfaces provide the benefits of multipwithout drawbacks.

• Syntax of a Java class is as follows:<modifier> class <name> [extends <superclas<declaration>*

}


cretary



Single Inheritance

Manager

+department : String = ""

Employee

+name : String = ""

+salary : double

+birthDate : Date

Director

+carAllowance : double

Engineer Se


+increaseAllowance()


Ac s are listed here.

Mo ass Universe

pri

def

pro

pub Yes



Access Control

cess modifiers on class member declaration

difier Same Class Same Package Subcl

vate Yes

ault Yes Yes

tected Yes Yes Yes

lic Yes Yes Yes


ed from a

fferent but with the

1.



Overriding Methods

• A subclass can modify behavior inheritparent class.

• A subclass can create a method with difunctionality than the parent’s methodsame:• Name• Return type1

• Argument list

In J2SE version 5, the return type can be a subclass of the overridden return type.


12345678910

123456789



Overriding Methods

public class Employee {protected String name;protected double salary;protected Date birthDate;

public String getDetails() {return “Name: “ + name + “\n” +

“Salary: “ + salary;}

}

public class Manager extends Employee {protected String department;

public String getDetails() {return “Name: “ + name + “\n” +

“Salary: “ + salary + "\n" +“Manager of: “ + department;

}}


Less

123

123

12345678



Overridden Methods Cannot BeAccessible

public class Parent {public void doSomething() {}

}

public class Child extends Parent {private void doSomething() {} // illegal

}

public class UseBoth {public void doOtherThing() {Parent p1 = new Parent();Parent p2 = new Child();p1.doSomething();p2.doSomething();

}}


ds

A s ethod using thesup

refer to its

the members ofthods.the superclass;



Invoking Overridden Metho

ubclass method may invoke a superclass mer keyword:

• The keyword super is used in a class tosuperclass.

• The keyword super is used to refer tosuperclass, both data attributes and me

• Behavior invoked does not have to be init can be further up in the hierarchy.


ds

123456789

123456789



Invoking Overridden Metho

public class Employee {private String name;private double salary;private Date birthDate;

public String getDetails() {return "Name: " + name + "\nSalary: " + salary;

}}

public class Manager extends Employee {private String department;

public String getDetails() {// call parent methodreturn super.getDetails()

+ “\nDepartment: " + department;}

}


y differentas access to

of different



Polymorphism

• Polymorphism is the ability to have manforms; for example, the Manager class hmethods from Employee class.

• An object has only one form.• A reference variable can refer to objects

forms.


Empl

// e.de// t// e



Polymorphism

oyee e = new Manager(); // legal

illegal attempt to assign Manager attributepartment = "Sales";he variable is declared as an Employee type,ven though the Manager object has that attribute


d as follows:

vocations have

of the declared has a method

based on theManager classtails method.



Virtual Method Invocation

• Virtual method invocation is performeEmployee e = new Manager();e.getDetails();

• Compile-time type and runtime type inthe following characteristics:• The method name must be a member

variable type; in this case Employeecalled getDetails.

• The method implementation used isruntime object’s type; in this case thehas an implementation of the getDe


s

ss type areple:

ss types aremple:



Heterogeneous Collection

• Collections of objects with the same clacalled homogeneous collections. For examMyDate[] dates = new MyDate[2];dates[0] = new MyDate(22, 12, 1964);dates[1] = new MyDate(22, 7, 1964);

• Collections of objects with different clacalled heterogeneous collections. For exaEmployee [] staff = new Employee[1024];staff[0] = new Manager();staff[1] = new Employee();staff[2] = new Engineer();


Bec ing is valid:

publpu

}}

// MTaxSManTaxR



Polymorphic Arguments

ause a Manager is an Employee, the follow

ic class TaxService {blic TaxRate findTaxRate(Employee e) {// calculate the employee’s tax rate

eanwhile, elsewhere in the application classervice taxSvc = new TaxService();ager m = new Manager();ate t = taxSvc.findTaxRate(m);


r

publpublpubl----

publif

}

}

}}



The instanceofOperato

ic class Employee extends Objectic class Manager extends Employeeic class Engineer extends Employee------------------------------------

ic void doSomething(Employee e) { ( e instanceof Manager ) {// Process a Managerelse if ( e instanceof Engineer ) {// Process an Engineerelse {// Process any other type of Employee


”



Casting Objects

public void doSomething(Employee e) {if ( e instanceof Manager ) {Manager m = (Manager) e;System.out.println(“This is the manager of

+ m.getDepartment());}// rest of operation

}


bject.y casting.wing

ne implicitly.s and checked

when runtime



Casting Objects

• Use instanceof to test the type of an o• Restore full functionality of an object b• Check for proper casting using the follo

guidelines:• Casts upward in the hierarchy are do• Downward casts must be to a subclas

by the compiler.• The object type is checked at runtime

errors can occur.




Overloading Methods

• Use overloading as follows:public void println(int i)public void println(float f)public void println(String s)

• Argument lists must differ.• Return types can be different.


ents

it multiple

array. For

););



Methods Using Variable Argum

• Methods using variable arguments permnumber of arguments in methods.For example:public class Statistics {public float average(int... nums) {int sum = 0;for ( int x : nums ) {sum += x;

}return ((float) sum) / nums.length;

}}

• The vararg parameter is treated as an example:float gradePointAverage = stats.average(4, 3, 4float averageAge = stats.average(24, 32, 27, 18


verloaded.

e DoB)

irst line of a



Overloading Constructors

• As with methods, constructors can be oAn example is:public Employee(String name, double salary, Datpublic Employee(String name, double salary)public Employee(String name, Date DoB)

• Argument lists must differ.• You can use the this reference at the f

constructor to call another constructor.


12 0;34567 DoB) {8910111213141516171819



Overloading Constructors

public class Employee { private static final double BASE_SALARY = 15000.0 private String name; private double salary; private Date birthDate;

public Employee(String name, double salary, Date this.name = name; this.salary = salary; this.birthDate = DoB; }public Employee(String name, double salary) {

this(name, salary, null); } public Employee(String name, Date DoB) { this(name, BASE_SALARY, DoB); }// more Employee code...

}


ed

iables from the

ctor from the

ors.



Constructors Are Not Inherit

• A subclass inherits all methods and varsuperclass (parent class).

• A subclass does not inherit the construsuperclass.

• Two ways to include a constructor are:• Use the default constructor.• Write one or more explicit construct


ctors

st place a call tor.or by theper.structor, thenper() that callshich could be

s, but does noten a compiler



Invoking Parent Class Constru

• To invoke a parent constructor, you musuper in the first line of the constructo

• You can call a specific parent constructarguments that you use in the call to su

• If no this or super call is used in a conthe compiler adds an implicit call to suthe parent no argument constructor (wthe default constructor).If the parent class defines constructorprovide a no-argument constructor, therror message is issued.


ctors

1234 dept) {56789101112 s: no super()13141516



Invoking Parent Class Constru

public class Manager extends Employee {private String department;

public Manager(String name, double salary, Stringsuper(name, salary);department = dept;

}public Manager(String name, String dept) {super(name);department = dept;

}public Manager(String dept) { // This code faildepartment = dept;

}//more Manager code...

}


ects: A

Me occurs.

Ins s recursively:

then skip to

t super call,

initializers.ructor.



Constructing and Initializing ObjSlight Reprise

mory is allocated and default initialization

tance variable initialization uses these step

1. Bind constructor parameters.2. If explicit this(), call recursively, and

Step 5.3. Call recursively the implicit or explici

except for Object.4. Execute the explicit instance variable5. Execute the body of the current const


Constructor and InitializationExamples

1 public class Object {2 public Object() {}3 }

1 public class Employee extends Object {2 private String name;3 private double salary = 15000.00;4 private Date birthDate;56 public Employee(String n, Date DoB) {7 // implicit super();8 name = n;9 birthDate = DoB;10 }11 public Employee(String n) {12 this(n, null);13 }14 }

1 public class Manager extends Employee {2 private String department;34 public Manager(String n, String d) {5 super(n);6 department = d;7 }8 }



mples

0 Ba 0.0. values (0 or null)

1 Ca 1. les" 1. 1. ", DoB=null or Object



Constructor and Initialization Exa

sic initialization1 Allocate memory for the complete Manager object2 Initialize all instance variables to their defaultll constructor: Manager("Joe Smith", "Sales")1 Bind constructor parameters: n="Joe Smith", d="Sa2 No explicit this() call3 Call super(n) for Employee(String)1.3.1 Bind constructor parameters: n="Joe Smith"1.3.2 Call this(n, null) for Employee(String, Date) 1.3.2.1 Bind constructor parameters: n="Joe Smith 1.3.2.2 No explicit this() call 1.3.2.3 Call super() for Object() 1.3.2.3.1 No binding necessary 1.3.2.3.2 No this() call 1.3.2.3.3 No super() call (Object is the root) 1.3.2.3.4 No explicit variable initialization f 1.3.2.3.5 No method body to call


mples

alary=15000.00; ; 1. 1.



Constructor and Initialization Exa

1.3.2.4 Initialize explicit Employee variables: s 1.3.2.5 Execute body: name="Joe Smith"; date=null1.3.3 - 1.3.4 Steps skipped1.3.5 Execute body: No body in Employee(String)4 No explicit initializers for Manager5 Execute body: department="Sales"


s in Java.ause implies



The ObjectClass

• The Object class is the root of all classe• A class declaration with no extends cl

extends Object. For example:public class Employee { ...}

is equivalent to:public class Employee extends Object { ...}

• Two important methods are:• equals

• toString


rences arehe same object).ts are equal but

als method

ethod touality.emethod if you



The equalsMethod

• The == operator determines if two refeidentical to each other (that is, refer to t

• The equalsmethod determines if objecnot necessarily identical.

• The Object implementation of the equuses the == operator.

• User classes can override the equals mimplement a domain-specific test for eq

• Note: You should override thehashCodoverride the equals method.


12345678910



An equalsExample

public class MyDate { private int day; private int month; private int year;

public MyDate(int day, int month, int year) { this.day = day; this.month = month; this.year = year; }


1112131415161718192021222324252627



An equalsExample

public boolean equals(Object o) {boolean result = false;if ( (o != null) && (o instanceof MyDate) ) {MyDate d = (MyDate) o;if ( (day == d.day) && (month == d.month)

&& (year == d.year) ) {result = true;

}}return result;

}

public int hashCode() {return (day ^ month ^ year);

}}


1234567 e2");89 date2");10111213 ;1415 e2");16



An equalsExample

class TestEquals {public static void main(String[] args) {

MyDate date1 = new MyDate(14, 3, 1976); MyDate date2 = new MyDate(14, 3, 1976);

if ( date1 == date2 ) { System.out.println("date1 is identical to dat } else { System.out.println("date1 is not identical to }

if ( date1.equals(date2) ) { System.out.println("date1 is equal to date2") } else { System.out.println("date1 is not equal to dat }


171819202122 e2");2324 date2");252627

Th

datedateset date



An equalsExample

System.out.println("set date2 = date1;"); date2 = date1;

if ( date1 == date2 ) { System.out.println("date1 is identical to dat } else { System.out.println("date1 is not identical to } }}

is example generates the following output:

1 is not identical to date21 is equal to date2date2 = date1;1 is identical to date2


Th acteristics:

ing.ation.ation about a

c method to



The toStringMethod

e toString method has the following char

• This method converts an object to a Str• Use this method during string concaten• Override this method to provide inform

user-defined object in readable format.• Use the wrapper class’s toString stati

convert primitive types to a String.


Lo



Wrapper Classes

ok at primitive data elements as objects.

Primitive Data Type Wrapper Class

boolean Boolean

byte Byte

char Character

short Short

int Integer

long Long

float Float

double Double


An

int Inte oxingint

Oth

int int



Wrapper Classes

example of a wrapper class is:

pInt = 420;ger wInt = new Integer(pInt); // this is called bp2 = wInt.intValue(); // this is called unboxing

er methods are:

x = Integer.valueOf(str).intValue();x = Integer.parseInt(str);


es

Au

ject equivalent

xingg

n dealing with

metic

ng



Autoboxing of Primitive Typ

toboxing has the following description:

• Conversion of primitive types to the ob• Wrapper classes not always needed• Example:

int pInt = 420;Integer wInt = pInt; // this is called autoboint p2 = wInt; // this is called autounboxin

• Language feature used most often whecollections

• Wrapped primitives also usable in arithexpressions

• Performance loss when using autoboxi

Sun

Java™ Programmi

res


ng Language

Module 7

Advanced Class Featu


itializersbles



Objectives

• Create static variables, methods, and in• Create final classes, methods, and varia• Create and use enumerated types• Use the static import statement• Create abstract classes and methods• Create and use an interface


by all instances

om being



Relevance

• How can you create a constant?• How can you declare data that is shared

of a given class?• How can you keep a class or method fr

subclassed or overridden?


ier on variables,

bute or methodather than any

ass members,



The staticKeyword

• Thestatickeyword is used as a modifmethods, and nested classes.

• The static keyword declares the attriis associated with the class as a whole rparticular instance of that class.

• Thus static members are often called clsuch as class attributes or class methods.


Cla s of a class:

282930313233343536



Class Attributes

ss attributes are shared among all instance

public class Count {private int serialNumber;public static int counter = 0;

public Count() {counter++;serialNumber = counter;

}}

c1 : Count

Count

serialNumber=1

-serialNumber : int

+counter : int = 0

c2 : Count

serialNumber=2

«instanceOf»«instanceOf»


If t

12345678

it c out an instance:

12345



Class Attributes

he static member is public:

public class Count1 {private int serialNumber;public static int counter = 0;

public Count1() { counter++; serialNumber = counter; }}

an be accessed from outside the class with

public class OtherClass { public void incrementNumber() {

Count1.counter++; }}


You

12345678910111213



Class Methods

can create static methods:

public class Count2 { private int serialNumber; private static int counter = 0;

public static int getTotalCount() { return counter; }

public Count2() {counter++;

serialNumber = counter; }}


You instance of thecla

123456789

Th

NumbNumb



Class Methods

can invoke static methods without anyss to which it belongs:

public class TestCounter { public static void main(String[] args) { System.out.println("Number of counter is " + Count2.getTotalCount()); Count2 counter = new Count2(); System.out.println("Number of counter is " + Count2.getTotalCount()); }}

e output of the TestCounter program is:

er of counter is 0er of counter is 1


Sta es:

12345678



Class Methods

tic methods cannot access instance variabl

public class Count3 { private int serialNumber; private static int counter = 0;

public static int getSerialNumber() { return serialNumber; // COMPILER ERROR! }}


that does not

hen the class is

ze static (class)



Static Initializers

• A class can contain code in a static blockexist within a method body.

• Static block code executes once only, wloaded.

• Usually, a static block is used to initialiattributes.


1234 ter").intValue();56

123 );45

Th is:

javacoun



Static Initializers

public class Count4 { public static int counter;static {

counter = Integer.getInteger("myApp.Count4.coun}

}

public class TestStaticInit { public static void main(String[] args) { System.out.println("counter = "+ Count4.counter }}

e output of the TestStaticInit program

-DmyApp.Count4.counter=47 TestStaticInitter = 47


, but thatthe declaration;

t be set in every

be set in the



The finalKeyword

• You cannot subclass a final class.• You cannot override a final method.• A final variable is a constant.• You can set a final variable once only

assignment can occur independently ofthis is called a blank final variable.• A blank final instance attribute mus

constructor.• A blank final method variable must

method body before being used.


Co

publpr 3.2;..

}



Final Variables

nstants are static final variables.

ic class Bank {ivate static final double DEFAULT_INTEREST_RATE = . // more declarations


12345678910111213141516171819



Blank Final Variables

public class Customer {

private final long customerID;

public Customer() {customerID = createID();

}

public long getID() {return customerID;

}

private long createID() {return ... // generate new ID

}

// more declarations

}


iom

En gramming.1234567891011121314151617



Old-Style Enumerated Type Id

umerated types are a common idiom in pro0

package cards.domain;

public class PlayingCard {

// pseudo enumerated type public static final int SUIT_SPADES = 0; public static final int SUIT_HEARTS = 1; public static final int SUIT_CLUBS = 2; public static final int SUIT_DIAMONDS = 3;

private int suit; private int rank;

public PlayingCard(int suit, int rank) { this.suit = suit; this.rank = rank; }


m

2223242526272829303132333435363738394041



Old-Style Enumerated Type Idio

public String getSuitName() { String name = ““; switch ( suit ) { case SUIT_SPADES: name = “Spades”; break; case SUIT_HEARTS: name = “Hearts”; break; case SUIT_CLUBS: name = “Clubs”; break; case SUIT_DIAMONDS: name = “Diamonds”; break; default: System.err.println(“Invalid suit.”); } return name; }


m

Old

12345678910 ()11 ;1213 .1415 ()16 ;1718



Old-Style Enumerated Type Idio

-style idiom is not type-safe:

package cards.tests;

import cards.domain.PlayingCard;

public class TestPlayingCard { public static void main(String[] args) {

PlayingCard card1 = new PlayingCard(PlayingCard.SUIT_SPADES, 2); System.out.println(“card1 is the “ + card1.getRank + “ of “ + card1.getSuitName())

// You can create a playing card with a bogus suit PlayingCard card2 = new PlayingCard(47, 2); System.out.println(“card2 is the “ + card2.getRank + “ of “ + card2.getSuitName()) }}


iom

Th lems:



Old-Style Enumerated Type Id

is enumerated type idiom has several prob

• Not type-safe• No namespace• Brittle character• Uninformative printed values


e

No es:

123456789



The New Enumerated Typ

w you can create type-safe enumerated typ


public enum Suit { SPADES, HEARTS, CLUBS, DIAMONDS}


e

Us

123456789101112131415




ing enumerated types is easy:


public class PlayingCard {

private Suit suit; private int rank;

public PlayingCard(Suit suit, int rank) { this.suit = suit; this.rank = rank; }

public Suit getSuit() { return suit; }


161718192021222324252627282930313233343536



The New Enumerated Type

public String getSuitName() { String name = ““; switch ( suit ) { case SPADES: name = “Spades”; break; case HEARTS: name = “Hearts”; break; case CLUBS: name = “Clubs”; break; case DIAMONDS: name = “Diamonds”; break; default: // No need for error checking as the Suit // enum is finite. } return name; }


e

En

1234567891011 ank()12 ());1314151617




umerated types are type-safe:


import cards.domain.PlayingCard;import cards.domain.Suit;


PlayingCard card1 = new PlayingCard(Suit.SPADES, 2); System.out.println(“card1 is the “ + card1.getR + “ of “ + card1.getSuitName

// PlayingCard card2 = new PlayingCard(47, 2); // This will not compile. }}


es

En thods:123456789101112131415161718



Advanced Enumerated Typ

umerated types can have attributes and mepackage cards.domain;

public enum Suit { SPADES (“Spades”), HEARTS (“Hearts”), CLUBS (“Clubs”), DIAMONDS (“Diamonds”);

private final String name;

private Suit(String name) { this.name = name; }

public String getName() { return name; }}


es

Pu ssible:

1234567891011 ank()12 etName());1314 , 2);151617



Advanced Enumerated Typ

blic methods on enumerated types are acce


import cards.domain.PlayingCard;import cards.domain.Suit;


PlayingCard card1 = new PlayingCard(Suit.SPADES, 2); System.out.println(“card1 is the “ + card1.getR + “ of “ + card1.getSuit().g

// NewPlayingCard card2 = new NewPlayingCard(47 // This will not compile. }}


ers from a class:er_name>;

idually or

nstants:;



Static Imports

• A static import imports the static membimport static <pkg_list>.<class_name>.<membORimport static <pkg_list>.<class_name>.*;

• A static import imports members indivcollectively:import static cards.domain.Suit.SPADES;ORimport static cards.domain.Suit.*;

• There is no need to qualify the static coPlayingCard card1 = new PlayingCard(SPADES, 2)

• Use this feature sparingly.


An

12345678910 ank()11 etName());1213 , 2);141516



Static Imports

example of a static import is:


import cards.domain.PlayingCard;import static cards.domain.Suit.*;


PlayingCard card1 = new PlayingCard(SPADES, 2); System.out.println(“card1 is the “ + card1.getR + “ of “ + card1.getSuit().g

// NewPlayingCard card2 = new NewPlayingCard(47 // This will not compile. }}


Th this:

hicle

RiverBarge



Abstract Classes

e design of the Shipping system looks like

Ve

Truck

Companyfleet

0..*

shipping

domainShippingMain «Uses»

FuelNeedsReport «Uses»

reports


Fle

12345 s6789101112 ;131415



Abstract Classes

et initialization code is shown here:

public class ShippingMain {public static void main(String[] args) {Company c = new Company();

// populate the company with a fleet of vehiclec.addVehicle( new Truck(10000.0) );c.addVehicle( new Truck(15000.0) );c.addVehicle( new RiverBarge(500000.0) );c.addVehicle( new Truck(9500.0) );c.addVehicle( new RiverBarge(750000.0) );

FuelNeedsReport report = new FuelNeedsReport(c)report.generateText(System.out);

}}


12345678910111213 + ) {1415



Abstract Classes

public class FuelNeedsReport {private Company company;

public FuelNeedsReport(Company company) {this.company = company;

}

public void generateText(PrintStream output) {Vehicle1 v;double fuel;double total_fuel = 0.0;

for ( int i = 0; i < company.getFleetSize(); i+v = company.getVehicle(i);


1617 fficency();1819 eeds "20212223 uel + " liters.");2425



Abstract Classes

// Calculate the fuel needed for this tripfuel = v.calcTripDistance() / v.calcFuelE

output.println("Vehicle " + v.getName() + " n+ fuel + " liters of fuel.");

total_fuel += fuel;}output.println("Total fuel needs is " + total_f

}}


An hich the fullim by the concretesub

e

() : double

: double

: double)



The Solution

abstract class models a class of objects in wplementation is not known but is suppliedclasses.

RiverBarg

Vehicle

+calcFuelEfficiency() : double

+calcTripDistance() : double

Truck

+calcFuelEfficiency() : double

+calcTripDistance() : double

+Truck(maxLoad : double)

{abstract}

«constructors»

«methods»

+calcFuelEfficiency

+calcTripDistance()

+RiverBarge(maxLoad

«constructors»

«methods»


Th

1234

Th n:

1234 a given load */567 ay */89



The Solution

e declaration of the Vehicle class is:

public abstract class Vehicle {public abstract double calcFuelEfficiency();public abstract double calcTripDistance();

}

e Truck class must create an implementatio

public class Truck extends Vehicle {public Truck(double maxLoad) {...}

public double calcFuelEfficiency() { /* calculate the fuel consumption of a truck at } public double calcTripDistance() { /* calculate the distance of this trip on highw }}


Lik nim

1234 ge */567 e river-ways */89



The Solution

ewise, the RiverBarge class must create aplementation:

public class RiverBarge extends Vehicle {public RiverBarge(double maxLoad) {...}

public double calcFuelEfficiency() { /* calculate the fuel efficiency of a river bar } public double calcTripDistance() { /* calculate the distance of this trip along th }}


lient code and.such a contractentation.

the same

interfaces.

s>]face>]* ] {



Interfaces

• A public interface is a contract between cthe class that implements that interface

• A Java interface is a formal declaration ofin which all methods contain no implem

• Many unrelated classes can implementinterface.

• A class can implement many unrelated• Syntax of a Java class is as follows:

<modifier> class <name> [extends <superclas[implements <interface> [,<inter

<member_declaration>*}


publpupupu

}



The Flyer Example

ic interface Flyer {blic void takeOff();blic void land();blic void fly();

+takeOff()

+land()

+fly()

«interface»

Flyer

+takeOff()

+land()

+fly()

Airplane


publpu

}pu

}pu

}}



The Flyer Example

ic class Airplane implements Flyer {blic void takeOff() {// accelerate until lift-off// raise landing gear

blic void land() {// lower landing gear// decelerate and lower flaps until touch-down// apply brakes

blic void fly() {// keep those engines running


)

an

ding()

et()



The Flyer Example

+takeOff()

+land()

+fly()

«interface»

Flyer

+takeOff()

+land()

+fly()

Airplane

+takeOff()

+land()

+fly()

Bird

+takeOff(

+land()

+fly()

Superm

+buildNest()

+layEggs()

+leapBuil

+stopBull


Kryptonian

eOff()

d()

()

perman

pBuilding()

pBullet()

()



The Flyer Example

Vehicle

Animal

+eat()

+takeOff()

+land()

+fly()

«interface»

Flyer

+takeOff()

+land()

+fly()

Airplane

+takeOff()

+land()

+fly()

Bird

+tak

+lan

+fly

Su

+buildNest()

+layEggs()

+lea

+sto

+eat() +eat


publpu */ }pu */ }pu */ }pu */ }pu */ }pu */ }

}



The Flyer Example

ic class Bird extends Animal implements Flyer {blic void takeOff() { /* take-off implementationblic void land() { /* landing implementationblic void fly() { /* fly implementationblic void buildNest() { /* nest building behaviorblic void layEggs() { /* egg laying behaviorblic void eat() { /* override eating behavior


Kryptonian

takeOff()

land()

fly()

Superman

leapBuilding()

stopBullet()

eat()



The Flyer Example

Vehicle

Animal

+eat()

+takeOff()

+land()

+fly()

«interface»

Flyer

+takeOff()

+land()

+fly()

Airplane

+takeOff()

+land()

+fly()

Bird

+

+

+

+buildNest()

+layEggs()

+

+

+eat() +

HelicopterSeaPlane


publpu

}

pr

}}



The Flyer Example

ic class Airport {blic static void main(String[] args) {Airport metropolisAirport = new Airport();Helicopter copter = new Helicopter();SeaPlane sPlane = new SeaPlane();

metropolisAirport.givePermissionToLand(copter);metropolisAirport.givePermissionToLand(sPlane);

ivate void givePermissionToLand(Flyer f) {f.land();


keOff()

nd()

y()

interface»

Flyer

ff()

)

lane

Helicopter



Multiple Interface Example

+ta

+la

+fl

«

+takeO

+land(

+fly()

Airp

+dock()

+cruise()

«interface»

Sailer

SeaPlane

+dock()

+cruise()

Vehicle

RiverBarge

+dock()

+cruise()


publpu

}

pr

}}



Multiple Interface Example

ic class Harbor {blic static void main(String[] args) {Harbor bostonHarbor = new Harbor();RiverBarge barge = new RiverBarge();SeaPlane sPlane = new SeaPlane();

bostonHarbor.givePermissionToDock(barge);bostonHarbor.givePermissionToDock(sPlane);

ivate void givePermissionToDock(Sailer s) {s.dock();


Int

sses are

interfacee classed classes

laring a class



Uses of Interfaces

erface uses include the following:

• Declaring methods that one or more claexpected to implement

• Determining an object’s programming without revealing the actual body of th

• Capturing similarities between unrelatwithout forcing a class relationship

• Simulating multiple inheritance by decthat implements several interfaces

Sun

Java™ Programmi

ons


ng Language

Module 8

Exceptions and Asserti


ts

exceptions

iate uses of



Objectives

• Define exceptions• Use try, catch, and finally statemen• Describe exception categories• Identify common exceptions• Develop programs to handle your own• Use assertions• Distinguish appropriate and inappropr

assertions• Enable assertions at runtime


do you resolve

y your codeng, what might

pend CPU programs?



Relevance

• In most programming languages, how runtime errors?

• If you make assumptions about the waworks, and those assumptions are wrohappen?

• Is it always necessary or desirable to expower testing assertions in production


ns – Illegaloundming here from code atn at all.



Exceptions and Assertions

• Exceptions handle unexpected situatioargument, network failure, or file not f

• Assertions document and test programassumptions – This can never be negative

• Assertion tests can be removed entirelyruntime, so the code is not slowed dow


orrect program

on class.ted as fatal or bugs are

Error class.

exceptions that



Exceptions

• Conditions that can readily occur in a care checked exceptions.These are represented by the Excepti

• Severe problems that normally are treasituations that probably reflect programunchecked exceptions.Fatal situations are represented by theProbable bugs are represented by theRuntimeException class.

• The API documentation shows checkedcan be thrown from a method.


123456789

javaSum

javaExce r input string: "two"

matException.java:48)



Exception Example

public class AddArguments { public static void main(String args[]) { int sum = 0; for ( String arg : args ) { sum += Integer.parseInt(arg); } System.out.println("Sum = " + sum); }}

AddArguments 1 2 3 4= 10

AddArguments 1 two 3.0 4ption in thread "main" java.lang.NumberFormatException: Foat java.lang.NumberFormatException.forInputString(NumberForat java.lang.Integer.parseInt(Integer.java:447)at java.lang.Integer.parseInt(Integer.java:497)at AddArguments.main(AddArguments.java:5)


t

1234567891011 eger.");121314

javaOne



The try-catchStatemen

public class AddArguments2 { public static void main(String args[]) {

try { int sum = 0;

for ( String arg : args ) {sum += Integer.parseInt(arg);

} System.out.println("Sum = " + sum);

} catch (NumberFormatException nfe) { System.err.println("One of the command-line "

+ "arguments is not an int}

}}

AddArguments2 1 two 3.0 4of the command-line arguments is not an integer.


nt

12345678 integer"9 uded in the sum.");1011121314

java[two sum.[3.0 sum.Sum



The try-catchStateme

public class AddArguments3 { public static void main(String args[]) { int sum = 0;

for ( String arg : args ) {try {sum += Integer.parseInt(arg);

} catch (NumberFormatException nfe) {System.err.println("[" + arg + "] is not an

+ " and will not be incl}

} System.out.println("Sum = " + sum); }}

AddArguments3 1 two 3.0 4] is not an integer and will not be included in the] is not an integer and will not be included in the= 5


nt

A t h clauses:

try //

} ca// wn

} ca// thrown

} ca//

}



The try-catchStateme

ry-catch statement can use multiple catc

{ code that might throw one or more exceptions

tch (MyException e1) { code to execute if a MyException exception is thro

tch (MyOtherException e2) { code to execute if a MyOtherException exception is

tch (Exception e3) { code to execute if any other exception is thrown


rent try-catchethod.thod and is not

ed abnormally.



Call Stack Mechanism

• If an exception is not handled in the curblock, it is thrown to the caller of that m

• If the exception gets back to the main mehandled there, the program is terminat


Th at alwaysexe

12345678



The finallyClause

e finally clause defines a block of code thcutes.

try { startFaucet(); waterLawn();} catch (BrokenPipeException e) {

logProblem(e); } finally { stopFaucet();}


icException

terException

rgumentException

ception

rflowError

oryError



Exception Categories

Throwable

Error

Exception

RuntimeException

IOException

Arithmet

NullPoin

IllegalA

FileNotFoundEx

VirtualMachineError

AssertionError

StackOve

OutOfMem

EOFException

SQLException




Common Exceptions

• NullPointerException

• FileNotFoundException

• NumberFormatException

• ArithmeticException

• SecurityException


e

Us

on by using the

on { ... }

Oth

eptions or

ptions.



The Handle or Declare Rul

e the handle or declare rule as follows:

• Handle the exception by using thetry-catch-finally block.

• Declare that the code causes an exceptithrows clause.void trouble() throws IOException { ... }void trouble() throws IOException, MyExcepti

er Principles

• You do not need to declare runtime excerrors.

• You can choose to handle runtime exce


tions

Th

by the

s thrown by the

Th

e overridden

by the



Method Overriding and Excep

e overriding method can throw:

• No exceptions• One or more of the exceptions thrown

overridden method• One or more subclasses of the exception

overridden method

e overriding method cannot throw:

• Additional exceptions not thrown by thmethod

• Superclasses of the exceptions thrown overridden method


tions

12345

12345

12 G345



Method Overriding and Excep

public class TestA { public void methodA() throws IOException { // do some file manipulation }}

public class TestB1 extends TestA { public void methodA() throws EOFException {

// do some file manipulation}

}

public class TestB2 extends TestA { public void methodA() throws Exception { // WRON

// do some file manipulation}

}


ns

1 ception {234 t port) {56789101112

Us the Exceptioncla n was made.



Creating Your Own Exceptio

public class ServerTimedOutException extends Ex private int port;

public ServerTimedOutException(String message, insuper(message);

this.port = port; }

public int getPort() { return port; }}

e the getMessage method, inherited from ss, to get the reason for which the exceptio


ption

A m exception:

123456789 t connect",10 nect);1112



Handling a User-Defined Exce

ethod can throw a user-defined, checked

public void connectMe(String serverName)throws ServerTimedOutException {

boolean successful; int portToConnect = 80;

successful = open(serverName, portToConnect);

if ( ! successful ) {throw new ServerTimedOutException("Could no portToCon

}}


eption

An o captureuse

12345 alternative");6789 e() +10 e1.getPort());111213



Handling a User-Defined Exc

other method can use a try-catch block tr-defined exceptions:

public void findServer() { try { connectMe(defaultServer); } catch (ServerTimedOutException e) { System.out.println("Server timed out, trying try { connectMe(alternativeServer); } catch (ServerTimedOutException e1) { System.out.println("Error: " + e1.getMessag " connecting to port " + } } }


ssion> ;

alse, then an

string and usedror message.



Assertions

• Syntax of an assertion is:assert <boolean_expression> ;assert <boolean_expression> : <detail_expre

• If <boolean_expression> evaluates fAssertionError is thrown.

• The second argument is converted to aas descriptive text in the AssertionEr


tions

Us umptions andint

Ina

meters of a

eck that can



Recommended Uses of Asser

e assertions to document and verify the assernal logic of a single method:

• Internal invariants• Control flow invariants• Postconditions and class invariants

ppropriate Uses of Assertions

• Do not use assertions to check the parapublic method.

• Do not use methods in the assertion chcause side-effects.


Th

12345

Th

123456



Internal Invariants

e problem is:

if (x > 0) {// do this

} else {// do that

}

e solution is:

if (x > 0) {// do this

} else {assert ( x == 0 );// do that, unless x is negative

}


For

12345678910 d suit";1112



Control Flow Invariants

example:

switch (suit) { case Suit.CLUBS: // ... break; case Suit.DIAMONDS: // ... break; case Suit.HEARTS: // ... break; case Suit.SPADES: // ... break; default: assert false : "Unknown playing car break;}


iants

For

1234 empty stack");567 ement */ ;8910111213



Postconditions and Class Invar

example:

public Object pop() { int size = this.getElementCount(); if (size == 0) { throw new RuntimeException("Attempt to pop from }

Object result = /* code to retrieve the popped el

// test the postconditionassert (this.getElementCount() == size - 1);

return result;}


n of

e runs as fast as

lt. Enables:

class, package,



Controlling Runtime EvaluatioAssertions

• If assertion checking is disabled, the codif the check was never there.

• Assertion checks are disabled by defauassertions with the following commandjava -enableassertions MyProgram

or:java -ea MyProgram

• Assertion checking can be controlled onand package hierarchy bases, see:docs/guide/language/assert.html

Sun

Java™ Programmi

Col amework


ng Language

Module 9

lections and Generics Fr


tions of therk

plementinges

n



Objectives

• Describe the Collections• Describe the general purpose implementa

core interfaces in the Collections framewo• Examine the Map interface• Examine the legacy collection classes• Create natural and custom ordering by im

the Comparable and Comparator interfac• Use generic collections• Use type parameters in generic classes• Refactor existing non-generic code• Write a program to iterate over a collectio• Examine the enhanced for loop


a group of

that group

lled elements;there is specific permitted.uplicates are

ates are



The Collections API

• A collection is a single object managing objects known as its elements.

• The Collections API contains interfacesobjects as one of the following:• Collection – A group of objects ca

implementations determine whetherordering and whether duplicates are

• Set – An unordered collection; no dpermitted.

• List – An ordered collection; duplicpermitted.


dList



The Collections API

Collection<<interface>>

Set<<interface>>

List<<interface>>

HashSet

ArrayList Linke

+add

+size+remove

+isEmpty+contains+iterator

+add

+get+remove

+set+indexOf+listIterator

TreeSet

<<interface >>

SortedSet


s

Th ations of thecor

Set

List

Dequ

Map



Collection Implementation

ere are several general purpose implemente interfaces (Set, List, Deque and Map)

HashTable

ResizableArray

BalancedTree Linked List Hash Table +

Linked List

HashSet TreeSet LinkedHashSet

ArrayList LinkedList

e ArrayDeque LinkedList

HashMap TreeMap LinkedHashMap


12345678910 dded11 dded121314

Th

[one



A SetExample

import java.util.*;public class SetExample { public static void main(String[] args) { Set set = new HashSet(); set.add("one"); set.add("second"); set.add("3rd"); set.add(new Integer(4)); set.add(new Float(5.0F)); set.add("second"); // duplicate, not a set.add(new Integer(4)); // duplicate, not a System.out.println(set); }}

e output generated from this program is:

, second, 5.0, 3rd, 4]


12345678910 dded11 dded121314

Th

[one



A ListExample

import java.util.*public class ListExample { public static void main(String[] args) { List list = new ArrayList(); list.add("one"); list.add("second"); list.add("3rd"); list.add(new Integer(4)); list.add(new Float(5.0F)); list.add("second"); // duplicate, is a list.add(new Integer(4)); // duplicate, is a System.out.println(list); }}

e output generated from this program is:

, second, 3rd, 4, 5.0, second, 4]


arrayskeys to values:

o values is not

viewed and

key-value pairs.ys in the map.ll values in the



The Map Interface

• Maps are sometimes called associative • A Map object describes mappings from

• Duplicate keys are not allowed• One-to-many mappings from keys t

permitted• The contents of the Map interface can be

manipulated as collections• entrySet – Returns a Set of all the• keySet – Returns a Set of all the ke• values – Returns a Collection of a

map.




The Map Interface API


12345678910111213141516 \n" + set2);1718



A MapExample

import java.util.*;public class MapExample {public static void main(String args[]) {Map map = new HashMap();map.put("one","1st");map.put("second", new Integer(2));map.put("third","3rd");// Overwrites the previous assignmentmap.put("third","III");// Returns set view of keysSet set1 = map.keySet();// Returns Collection view of valuesCollection collection = map.values();// Returns set view of key value mappingsSet set2 = map.entrySet();System.out.println(set1 + "\n" + collection + "

}}


Ou ram:

[sec[2, [sec



A MapExample

tput generated from the MapExample prog

ond, one, third]1st, III]ond=2, one=1st, third=III]


Co

e List

he Vector classethods.

ts the Map

f Hashtablelues.tsmethod thatumerationator interface.



Legacy Collection Classes

llections in the JDK include:

• The Vector class, which implements thinterface.

• The Stack class, which is a subclass of tand supports the push, pop, and peek m

• The Hashtable class, which implemeninterface.

• The Properties class is an extension othat only uses Strings for keys and va

• Each of these collections has an elemenreturns an Enumeration object. The Eninterface is incompatible with, the Iter


Th re useful forord

ral ordering to

er relation. Itering.

llections.



Ordering Collections

e Comparable and Comparator interfaces aering collections:

• The Comparable interface imparts natuclasses that implement it.

• The Comparator interface specifies ordcan also be used to override natural ord

• Both interfaces are useful for sorting co


Im ment it:

lemented to

implement the

ing objects that



The Comparable Interface

parts natural ordering to classes that imple

• Used for sorting• The compareTo method should be imp

make any class comparable:• int compareTo(Object o) method

• The String, Date, and Integer classesComparable interface

• You can sort the List elements containimplement the Comparable interface


the natural

errr



The Comparable Interface

• While sorting, the List elements followordering of the element types• String elements – Alphabetical ord• Date elements – Chronological orde• Integer elements – Numerical orde


erface

123456 int studentID,78 udentID == 09 ion();}101112131415161718



Example of the Comparable Int

import java.util.*;class Student implements Comparable {String firstName, lastName;int studentID=0;double GPA=0.0;public Student(String firstName, String lastName,double GPA) {if (firstName == null || lastName == null || st|| GPA == 0.0) {throw new IllegalArgumentExceptthis.firstName = firstName;this.lastName = lastName;this.studentID = studentID;this.GPA = GPA;

}public String firstName() { return firstName; }public String lastName() { return lastName; }public int studentID() { return studentID; }public double GPA() { return GPA; }


erface

19202122232425 than or before2627 than or after2829




// Implement compareTo method.public int compareTo(Object o) {double f = GPA-((Student)o).GPA;if (f == 0.0)return 0; // 0 signifies equalselse if (f<0.0)

return -1; // negative value signifies lesselse

return 1; // positive value signifies more}

}


erface

12345 01,4.0));6 8 ));7 ));8 2.3));910111213 %.1f\n",14 s.GPA());151617




import java.util.*;public class ComparableTest {public static void main(String[] args) {TreeSet studentSet = new TreeSet(); studentSet.add(new Student("Mike", "Hauffmann",1studentSet.add(new Student("John", "Lynn",102,2. studentSet.add(new Student("Jim", "Max",103, 3.6 studentSet.add(new Student("Kelly", "Grant",104,Object[] studentArray = studentSet.toArray();Student s;for(Object obj : studentArray){s = (Student) obj;System.out.printf("Name = %s %s ID = %d GPA =s.firstName(), s.lastName(), s.studentID(),

}}

}


erface

Ge

NameNameNameName




nerated Output:

= Kelly Grant ID = 104 GPA = 2.3 = John Lynn ID = 102 GPA = 2.8 = Jim Max ID = 103 GPA = 3.6 = Mike Hauffmann ID = 101 GPA = 4.0


m the natural

heComparable

You he Comparatorint

2) method



The Comparator Interface

• Represents an order relation• Used for sorting• Enables sorting in an order different fro

order• Used for objects that do not implement t

interface• Can be passed to a sort method

need the comparemethod to implement terface:

• int compare(Object o1, Object o


erface

1234567 udentID == 0 ||89101112131415161718



Example of the Comparator Int

class Student {String firstName, lastName;int studentID=0;double GPA=0.0;public Student(String firstName, String lastName,int studentID, double GPA) {if (firstName == null || lastName == null || stGPA == 0.0) throw new NullPointerException();this.firstName = firstName;this.lastName = lastName;this.studentID = studentID;this.GPA = GPA;

}public String firstName() { return firstName; }public String lastName() { return lastName; }public int studentID() { return studentID; }public double GPA() { return GPA; }

}


erface

12345 o2).firstName));67

1234567891011




import java.util.*;public class NameComp implements Comparator {public int compare(Object o1, Object o2) {return(((Student)o1).firstName.compareTo(((Student)

}}

import java.util.*;public class GradeComp implements Comparator {public int compare(Object o1, Object o2) {if (((Student)o1).GPA == ((Student)o2).GPA)return 0;else if (((Student)o1).GPA < ((Student)o2).GPA)return -1;elsereturn 1;

}}


erface

123456 101,4.0));7 .8 ));8 6));9 ,2.3));1011121314 = %.1f\n",15 s.GPA());161718




import java.util.*;public class ComparatorTest {public static void main(String[] args) {Comparator c = new NameComp();TreeSet studentSet = new TreeSet(c);studentSet.add(new Student("Mike", "Hauffmann",studentSet.add(new Student("John", "Lynn",102,2studentSet.add(new Student("Jim", "Max",103, 3.studentSet.add(new Student("Kelly", "Grant",104Object[] studentArray = studentSet.toArray();Student s;for(Object obj : studentArray) {s = (Student) obj;System.out.println("Name = %s %s ID = %d GPA s.firstName(), s.lastName(), s.studentID(),

}}

}


erface

NameNameNameName




= Jim Max ID = 0 GPA = 3.6 = John Lynn ID = 0 GPA = 2.8 = Kelly Grant ID = 0 GPA = 2.3 = Mike Hauffmann ID = 0 GPA = 4.0


Ge

hecked



Generics

nerics are described as follows:

• Provide compile-time type safety• Eliminate the need for casts• Provide the ability to create compiler-c

homogeneous collections


Us

Arralistint

Us

Arralistint



Generics

ing non-generic collections:

yList list = new ArrayList();.add(0, new Integer(42));total = ((Integer)list.get(0)).intValue();

ing generic collections:

yList<Integer> list = new ArrayList<Integer>();.add(0, new Integer(42));total = list.get(0).intValue();


1234567891011121314



Generic SetExample

import java.util.*;public class GenSetExample {public static void main(String[] args) {

Set<String> set = new HashSet<String>(); set.add("one"); set.add("second"); set.add("3rd");// This line generates compile error set.add(new Integer(4)); set.add("second");// Duplicate, not added System.out.println(set); }}


1234567891011121314151617



Generic Map Example

import java.util.*;

public class MapPlayerRepository { HashMap<String, String> players;

public MapPlayerRepository() { players = new HashMap<String, String> (); }

public String get(String position) { String player = players.get(position); return player; }

public void put(String position, String name) { players.put(position, name); }


meters

Sho

Cate

Clasdecl

> extendsts List <E>

Condecl

Metdecl

Varideclexam

;

Instadeclexam

ing> (10);

e> (10);



Generics: Examining Type Para

ws how to use type parameters

gory Non Generic Class Generic Class

saration

public class ArrayList extendsAbstractList implements List

public class ArrayList<EAbstractList<E> implemen

structoraration

public ArrayList(int capacity);

public ArrayList<E>(int capacity);

hodaration

public void add((Object o)

public Object get(int index)

public void add(E o)

public E get(int index)

ablearation

ples

ArrayList list1;

ArrayList list2;

ArrayList <String> list1

ArrayList <Date> list2;

ncearation

ples

list1 = new ArrayList(10);

list2 = new ArrayList(10);

list1= new ArrayList<Str

list2= new ArrayList<Dat




Generic Collections API


s

nt



Wild Card Type Parameter

Account

CheckingAccouSavingsAccount


e

1234 ngAccount>();567 error!8910 o cast required1112



The Type-Safety Guarante

public class TestTypeSafety {

public static void main(String[] args) { List<CheckingAccount> lc = new ArrayList<Checki

lc.add(new CheckingAccount("Fred")); // OK lc.add(new SavingsAccount("Fred")); // Compile

// therefore... CheckingAccount ca = lc.get(0); // Safe, n }}


78 ngAccount>();9 Account>();1011121314151617181920

In ckingAccountis a unt> is not anArr



The Invariance Challenge

List<Account> la; List<CheckingAccount> lc = new ArrayList<Checki List<SavingsAccount> ls = new ArrayList<Savings

//if the following were possible... la = lc; la.add(new CheckingAccount("Fred"));

//then the following must also be possible... la = ls; la.add(new CheckingAccount("Fred"));

//so... SavingsAccount sa = ls.get(0); //aarrgghh!!

fact, la=lc; is illegal, so even though a Chen Account, an ArrayList<CheckingAccoayList<Account>.


6 nt> lea) {78910111213 ngAccount>();14 Account>();15161718192021 error!2223



The Covariance Response

public static void printNames(List <? extends Accou for (int i=0; i < lea.size(); i++) { System.out.println(lea.get(i).getName());

} }

public static void main(String[] args) { List<CheckingAccount> lc = new ArrayList<Checki List<SavingsAccount> ls = new ArrayList<Savings

printNames(lc); printNames(ls);

//but... List<? extends Object> leo = lc; //OK leo.add(new CheckingAccount("Fred"));//Compile }}


on-

12345678

javaNote ions.Note

javaGene l to add(int,E)as a 1 wa



Generics: Refactoring Existing NGeneric Code

import java.util.*;public class GenericsWarning {public static void main(String[] args) {List list = new ArrayList();list.add(0, new Integer(42));int total = ((Integer)list.get(0).intValue();

}}

c GenericsWarning.java: GenericsWarning.java uses unchecked or unsafe operat: Recompile with -Xlint:unchecked for details.

c -Xlint:unchecked GenericsWarning.javaricsWarning.java:7: warning: [unchecked] unchecked cal member of the raw type java.util.ArrayListlist.add(0, new Integer(42)); ^rning


ry element in a

u to scan

tor, whichnd insert or

123456



Iterators

• Iteration is the process of retrieving evecollection.

• The basic Iterator interface allows yoforward through any collection.

• A List object supports the ListIteraallows you to scan the list backwards amodify elements.

List<Student> list = new ArrayList<Student>();// add some elementsIterator<Student> elements = list.iterator();while (elements.hasNext()) {System.out.println(elements.next());

}




Generic Iterator Interfaces

Iterator<E>«interface»

ListIterator<E>«interface»

+hasNext() : boolean+next() : E+remove()

+hasPrevious() : boolean+previous() : E+add(element : E)+set(element : E)


Th racteristics:

Ite

loop. to go wrong.



The Enhanced forLoop

e enhanced for loop has the following cha

• Simplified iteration over collections• Much shorter, clearer, and safer• Effective for arrays• Simpler when using nested loops• Iterator disadvantages removed

rators are error prone:

• Iterator variables occur three times per• This provides the opportunity for code


An ing:

r loop:

.hasNext() ; ){

collections:




enhanced for loop can look like the follow

• Using the iterator with a traditional fopublic void deleteAll(Collection<NameList> c){for ( Iterator<NameList> i = c.iterator() ; iNameList nl = i.next();nl.deleteItem();

}}

• Iterating using an enhanced for loop inpublic void deleteAll(Collection<NameList> c){for ( NameList nl : c ){nl.deleteItem();

}}


12345678




• Nested enhanced for loops:List<Subject> subjects=...;List<Teacher> teachers=...;List<Course> courseList = ArrayList<Course)();for (Subject subj: subjects) {for (Teacher tchr: teachers) {courseList.add(new Course(subj, tchr));

}}

Sun

Java™ Programmi


ng Language

Module 10

I/O Fundamentals


ne arguments

, and use them

treams, and



Objectives

• Write a program that uses command-liand system properties

• Examine the Properties class• Construct node and processing streams

appropriately• Serialize and deserialize objects• Distinguish readers and writers from s

select appropriately between them


s

se

he command the class name:

in the argsethod:



Command-Line Argument

• Any Java technology application can ucommand-line arguments.

• These string arguments are placed on tline to launch the Java interpreter afterjava TestArgs arg1 arg2 "another arg"

• Each command-line argument is placedarray that is passed to the static main mpublic static void main(String[] args)


s

1234 rgs[i] + "’");567

Ex

javaargsargsargs



Command-Line Argument

public class TestArgs { public static void main(String[] args) { for ( int i = 0; i < args.length; i++ ) { System.out.println("args[" + i + "] is ’" + a } }}

ample execution:

TestArgs arg0 arg1 "another arg"[0] is ’arg0’[1] is ’arg1’[2] is ’another arg’


laces the are

eturns a

ringoperty. to include a



System Properties

• System properties are a feature that repconcept of environment variables (whichplatform-specific).

• The System.getProperties method rProperties object.

• The getProperty method returns a Strepresenting the value of the named pr

• Use the -D option on the command linenew property.


pping of names

Enumeration

ringoperty.s collection into



The PropertiesClass

• ThePropertiesclass implements a mato values (a String-to-String map).

• The propertyNames method returns anof all property names.

• The getProperty method returns a Strepresenting the value of the named pr

• You can also read and write a propertiea file using load and store.


123456789



The PropertiesClass

import java.util.Properties;import java.util.Enumeration;

public class TestProperties { public static void main(String[] args) { Properties props = System.getProperties();

props.list(System.out);}

}


Th rogram:

java

Th

javasun.javajavajavafileusermyPr



The PropertiesClass

e following is an example test run of this p

-DmyProp=theValue TestProperties

e following is the (partial) output:

.runtime.name=Java(TM) SE Runtime Environmentboot.library.path=C:\jse\jdk1.6.0\jre\bin.vm.version=1.6.0-b105.vm.vendor=Sun Microsystems Inc..vm.name=Java HotSpot(TM) Client VM.encoding.pkg=sun.io.country=USop=theValue


or to a sink.a, also called an

a, also called an

.y, and pipes



I/O Stream Fundamentals

• A stream is a flow of data from a source• A source stream initiates the flow of dat

input stream.• A sink stream terminates the flow of dat

output stream.• Sources and sinks are both node streams• Types of node streams are files, memor

between threads or processes.


es

Str racter Streams

Sou der

Sin ter



Fundamental Stream Class

eam Byte Streams Cha

rce streams InputStream Rea

k streams OutputStream Wri


streams:

andled by

d by input

byte stream.haracter



Data Within Streams

• Java technology supports two types of character and byte.

• Input and output of character data is hreaders and writers.

• Input and output of byte data is handlestreams and output streams:• Normally, the term stream refers to a• The terms reader and writer refer to c

streams.


s



The InputStreamMethod

• The three basic read methods are:int read()int read(byte[] buffer)int read(byte[] buffer, int offset, int length)

• Other methods include:void close()int available()long skip(long n)boolean markSupported()void mark(int readlimit)void reset()


s

h)



The OutputStreamMethod

• The three basic write methods are:void write(int c)void write(byte[] buffer)void write(byte[] buffer, int offset, int lengt

• Other methods include:void close()void flush()




The ReaderMethods

• The three basic read methods are:int read()int read(char[] cbuf)int read(char[] cbuf, int offset, int length)

• Other methods include:void close()boolean ready()long skip(long n)boolean markSupported()void mark(int readAheadLimit)void reset()


h)



The WriterMethods

• The basic write methods are:void write(int c)void write(char[] cbuf)void write(char[] cbuf, int offset, int length)void write(String string)void write(String string, int offset, int lengt

• Other methods include:void close()void flush()


Ty ms

Fil StreamtStream

Mearr

InputStreamOutputStream

Mestr

Pip tStreamutStream



Node Streams

pe Character Streams Byte Strea

e FileReaderFileWriter

FileInputFileOutpu

mory:ay

CharArrayReaderCharArrayWriter

ByteArrayByteArray

mory:ing

StringReaderStringWriter

N/A

e PipedReaderPipedWriter

PipedInpuPipedOutp


Th ng a manualbu

java

123456789101112131415



A Simple Example

is program performs a copy file operation usiffer:

TestNodeStreams file1 file2

import java.io.*;public class TestNodeStreams { public static void main(String[] args) { try {

FileReader input = new FileReader(args[0]);try {FileWriter output = new FileWriter(args[1]);try {char[] buffer = new char[128];int charsRead;

// read the first buffercharsRead = input.read(buffer);while ( charsRead != -1 ) {// write buffer to the output file


161718192021222324252627282930



A Simple Example

output.write(buffer, 0, charsRead);

// read the next buffercharsRead = input.read(buffer);

}

} finally {output.close();}

} finally {input.close();}

} catch (IOException e) {e.printStackTrace();

}}

}


Th ng a built-inbu

java

123456 ut);789 utput);101112131415



Buffered Streams

is program performs a copy file operation usiffer:

TestBufferedStreams file1 file2

import java.io.*;public class TestBufferedStreams {public static void main(String[] args) {try {FileReader input = new FileReader(args[0]);BufferedReader bufInput = new BufferedReader(inptry {FileWriter output = new FileWriter(args[1]);BufferedWriter bufOutput= new BufferedWriter(otry {String line;// read the first lineline = bufInput.readLine();while ( line != null ) {// write the line out to the output file


16 );1718192021222324252627282930313233



Buffered Streams

bufOutput.write(line, 0, line.length()bufOutput.newLine();// read the next lineline = bufInput.readLine();

}} finally {bufOutput.close();

}} finally {bufInput.close();

}} catch (IOException e) {e.printStackTrace();

}}

}


Program

Data Sink



I/O Stream Chaining

Data Source

FileInputStreamBufferedInputStream

DataInputStream

Program

FileOutputStreamBufferedOutputStream

DataOutputStream

Input Stream Chain

Output Stream Chain


Ty ams

Bu InputStreamOutputStream

Filt putStreamtputStream

Cobetand

Perobjser

putStreamtputStream



Processing Streams

pe Character Streams Byte Stre

ffering BufferedReaderBufferedWriter

BufferedBuffered

ering FilterReaderFilterWriter

FilterInFilterOu

nvertingween bytes character

InputStreamReaderOutputStreamWriter

formingectialization

ObjectInObjectOu


Ty ams

Percon

tStreamutStream

Co erInputStream

Pee InputStream

Pri eam



Processing Streams

pe Character Streams Byte Stre

forming dataversion

DataInpuDataOutp

unting LineNumberReader LineNumb

king ahead PushbackReader Pushback

nting PrintWriter PrintStr


rchy

InataInputStream

shbackInputStream

fferedInputStream

ineNumberInputStream



The InputStreamClass Hiera

putStream

FileInputStream

ObjectInputStream

PipedInputStream

StringBufferInputStream

FilterInputStream

ByteArrayInputStream

D

Pu

Bu

L

SequenceInputStream


archy

Ou

ataOutputStream

rintStreamrintStream

ufferedOutputStream



The OutputStreamClass Hier

tputStream

FileOutputStream

ObjectOutputStream

FilterOutputStream

ByteArrayOutputStream

D

PP

B

PipedOutputStream


Thees

m (called object process of

eam writes the data memberstream, followed.tream reads the class to matchvalues from the

nce of that class.ished if files (ors.



The ObjectInputStreamandObjectOutputStreamClass

• The Java API provides a standard mechanisserialization) that completely automates thewriting and reading objects from streams.

• When writing an object, the object input strclass name, followed by a description of theof the class, in the order they appear in the sby the values for all the fields on that object

• When reading an object, the object output sname of the class and the description of theagainst the class in memory, and it reads thestream to populate a newly allocation insta

• Persistent storage of objects can be accomplother persistent storage) are used as stream


Review



Input Chaining Combinations: A


O Review



utput Chaining Combinations: A


the objects as a later when

lds of the object

elds of the

because theirtem-specific



Serialization

• Serialization is a mechanism for savingsequence of bytes and rebuilding themneeded.

• When an object is serialized, only the fieare preserved

• When a field references an object, the fireferenced object are also serialized

• Some object classes are not serializablefields represent transient operating sysinformation.


s

12345678910111213141516171819



The SerializeDateClas

import java.io.*;import java.util.Date;

public class SerializeDate {

SerializeDate() { Date d = new Date ();

try { FileOutputStream f = new FileOutputStream ("date.ser"); ObjectOutputStream s = new ObjectOutputStream (f); s.writeObject (d); s.close (); } catch (IOException e) { e.printStackTrace (); } }


s

2021222324



The SerializeDateClas

public static void main (String args[]) { new SerializeDate(); }}


ss

123456789101112131415161718



The DeSerializeDateCla

import java.io.*;import java.util.Date;

public class DeSerializeDate {

DeSerializeDate () { Date d = null;

try { FileInputStream f = new FileInputStream ("date.ser"); ObjectInputStream s = new ObjectInputStream (f); d = (Date) s.readObject (); s.close (); } catch (Exception e) { e.printStackTrace (); }


ss

19202122232425262728



The DeSerializeDateCla

System.out.println( "Deserialized Date object from date.ser"); System.out.println("Date: "+d); }

public static void main (String args[]) { new DeSerializeDate();}

}


y

R

FileReader

neNumberReader

backReader



The ReaderClass Hierarch

eader

BufferedReader

CharArrayReader

PipedReader

FilterReader

StringReader

InputStreamReader

Li

Push


y

W FileWriter



The WriterClass Hierarch

riter

BufferedWriter

CharArrayWriter

PrintWriter

PipedWriter

FilterWriter

StringWriter

OutputStreamWriter

Sun

Java™ Programmi

/O


ng Language

Module 11

Console I/O and File I




Objectives

• Read data from the console• Write data to the console• Describe files and file I/O


o write to

Stream. read from

tream.o write to

Stream.



Console I/O

• The variable System.out enables you tstandard output.System.out is an object of type Print

• The variable System.in enables you tostandard input.System.in is an object of type InputS

• The variable System.err enables you tstandard error.System.err is an object of type Print


t

ent and a

t without a

verloaded fornt, long,ject, and

ect) methodsent.



Writing to Standard Outpu

• The println methods print the argumnewline character (\n).

• The print methods print the argumennewline character.

• The print and println methods are omost primitive types (boolean, char, ifloat, and double) and for char[], ObString.

• The print(Object) and println(Objcall the toString method on the argum


ut

123456789101112 +13 xit");



Reading From Standard Inp

import java.io.*;

public class KeyboardInput {public static void main (String args[]) {String s;// Create a buffered reader to read// each line from the keyboard.InputStreamReader ir= new InputStreamReader(System.in);

BufferedReader in = new BufferedReader(ir);

System.out.println("Unix: Type ctrl-d to exit.""\nWindows: Type ctrl-z to e


ut

1415 reen.161718192021222324 tions.25262728



Reading From Standard Inp

try {// Read each input line and echo it to the scs = in.readLine();while ( s != null ) {System.out.println("Read: " + s);s = in.readLine();

}

// Close the buffered reader.in.close();

} catch (IOException e) { // Catch any IO excepe.printStackTrace();

}}

}


y as follows:

l);

this table.

Co

%s ling the

%d cimal value.

%f es scientific

%n .

%%



Simple Formatted Output

• You can use the formatting functionalitout.printf(“name count\n”);String s = String.format(“%s %5d%n”, user, tota

• Common formatting codes are listed in

de Description

Formats the argument as a string, usually by caltoString method on the object.

%o %x Formats an integer, as a decimal, octal, or hexade

%g Formats a floating point number. The %g code usnotation.

Inserts a newline character to the string or stream

Inserts the % character to the string or stream.


input function.ole inputms.

m);

ue);



Simple Formatted Input

• The Scanner class provides a formatted• A Scanner class can be used with cons

streams as well as file or network strea• You can read console input as follows:

1 import java.io.*;2 import java.util.Scanner;3 public class ScanTest {4 public static void main(String [] args) {5 Scanner s = new Scanner(System.in);6 String param = s.next();7 System.out.println("the param 1" + para8 int value = s.nextInt();9 System.out.println("second param" + val10 s.close();11 }12 }


Th ollowing:



Files and File I/O

e java.io package enables you to do the f

• Create File objects• Manipulate File objects• Read and write to file streams


t

Th

;

file.txt");

Dir gramminglan presents adir , for example:



Creating a New FileObjec

e File class provides several utilities:

• File myFile;

• myFile = new File("myfile.txt")

• myFile = new File("MyDocs", "my

ectories are treated like files in the Java proguage. You can create a File object that reectory and then use it to identify other files

File myDir = new File("MyDocs");myFile = new File(myDir, "myfile.txt");


s



The FileTests and Utilitie

• File information:String getName()String getPath()String getAbsolutePath()String getParent()long lastModified()long length()

• File modification:boolean renameTo(File newName)boolean delete()

• Directory utilities:boolean mkdir()String[] list()


s



The FileTests and Utilitie

• File tests:boolean exists()boolean canWrite()boolean canRead()boolean isFile()boolean isDirectory()boolean isAbsolute();boolean is Hidden();


aracters.e the readLine

haracters.e print and



File Stream I/O

• For file input:• Use the FileReader class to read ch• Use the BufferedReader class to us

method.• For file output:

• Use the FileWriter class to write c• Use the PrintWriter class to use th

println methods.


A fi

12345678910111213



File Input Example

le input example is:

import java.io.*;public class ReadFile { public static void main (String[] args) { // Create file File file = new File(args[0]);

try { // Create a buffered reader

// to read each line from a file. BufferedReader in

= new BufferedReader(new FileReader(file)); String s;


14 o the screen.1516171819202122232425 ;26272829303132



Printing a File

// Read each line from the file and echo it ts = in.readLine();

while ( s != null ) {System.out.println("Read: " + s);s = in.readLine();

}// Close the buffered readerin.close();

} catch (FileNotFoundException e1) {// If this file does not exist

System.err.println("File not found: " + file)

} catch (IOException e2) {// Catch any other IO exceptions.

e2.printStackTrace();}

}}


123456789 from standard in.1011121314151617



File Output Example

import java.io.*;

public class WriteFile {public static void main (String[] args) {// Create fileFile file = new File(args[0]);

try {// Create a buffered reader to read each lineInputStreamReader isr= new InputStreamReader(System.in);

BufferedReader in = new BufferedReader(isr); // Create a print writer on this file. PrintWriter out = new PrintWriter(new FileWriter(file)); String s;


1819202122 reen.2324252627 nt writer.282930313233343536



File Output Example

System.out.print("Enter file text. "); System.out.println("[Type ctrl-d to stop.]");

// Read each input line and echo it to the sc while ((s = in.readLine()) != null) { out.println(s); }

// Close the buffered reader and the file pri in.close(); out.close();

} catch (IOException e) { // Catch any IO exceptions. e.printStackTrace(); } }}

Sun

Java™ Programmi

Build Swing API


ng Language

Module 12

ing Java GUIs Using the


ainers,

d special-

del



Objectives

• Describe the JFC Swing technology• Define Swing• Identify the Swing packages• Describe the GUI building blocks: cont

components, and layout managers• Examine top-level, general-purpose, an

purpose properties of container• Examine components• Examine layout managers• Describe the Swing single-threaded mo• Build a GUI using Swing components


lasses

Jav l User Interface(GU



What Are the Java Foundation C(JFC)?

a Foundation Classes are a set of GraphicaI) support packages, including:

• Abstract Window Toolkit (AWT)• The Swing component set• 2D graphics• Pluggable look-and-feel• Accessibility• Drag-and-drop• Internationalization


those in the

le look-and feel



What Is Swing?

• An enhanced GUI component set• Provides replacement components for

original AWT• Has special features, such as a pluggab


V

C

mponent

UIject

UIManager



Swing Architecture

• Has its roots in theModel-View-Controller(MVC) architecture

• The Swing componentsfollow Separable ModelArchitecture

M

Co

ObM


Pa

jav orchooser

jav echooser

jav le

jav e

jav t

jav t.html

jav t.html.parser

jav t.rtf

jav o



Swing Packages

ckage Name Package Name

ax.swing javax.swing.col

ax.swing.border javax.swing.fil

ax.swing.event javax.swing.tab

ax.swing.undo javax.swing.tre

ax.swing.plaf javax.swing.tex

ax.swing.plaf.basic javax.swing.tex

ax.swing.plaf.metal javax.swing.tex

ax.swing.plaf.multi javax.swing.tex

ax.swing.plaf.synth javax.swing.und


Java

A S ollowingele

tainment

onents that are

laying out



Examining the Composition of aTechnology GUI

wing API-based GUI is composed of the fments:

• Containers – Are on top of the GUI conhierarchy.

• Components – Contain all the GUI compderived from the JComponent class.

• Layout Managers – Are responsible forcomponents in a container.


Java



Examining the Composition of aTechnology GUI

ContainerComponents

Layout Managers


Sw ain categories:

plitPane, and

e



Swing Containers

ing containers can be classified into three m

• Top-level containers:• JFrame, JWindow, and JDialog

• General-purpose containers:• JPanel, JScrollPane,JToolBar,JS

JTabbedPane

• Special-purpose containers:• JInternalFrame and JLayeredPan




Top-Level Containers


Sw s:

nents



Swing Components

ing components can be broadly classified a

• Buttons• Text components• Uneditable information display compo• Menus• Formatted display components• Other basic controls


y



Swing Component Hierarch


Sw d into threecat

Field (for user

ext in plain text,

Pane (displays



Text Components

ing text components can be broadly divideegories.

• Text controls –JTextField,JPasswordinput)

• Plain text areas –JTextArea (displays talso for multi-line user input

• Styled text areas – JEditorPane, JTextformatted text)


es

Co

commonponent.

Co

properties.



Swing Component Properti

mmon component properties:

• All the Swing components share some properties because they all extend JCom

mponent-specific properties:

• Each component defines more specific


ties

Pro

Bor

Bacandcol

Fon

Op

Mami

Ali

Pre )



Common Component Proper

perty Methods

der Border getBorder()void setBorder(Border b)

kgroundforeground

or

void setBackground(Color bg)void setForeground(Color bg)

t void setFont(Font f)

aque void setOpaque(boolean isOpaque)

ximum andnimum size

void setMaximumSize(Dimension d)void setMinimumSize(Dimension d)

gnment void setAlignmentX(float ax)void setAlignmentY(float ay)

ferred size void setPreferredSize(Dimension ps


ties

Th omboBox.

Pro

Ma count)

Mo cbm)

Sel

Sel

Item

Ren nderer ar)

Ed ag)



Component-Specific Proper

e following shows properties specific to JC

perties Methods

ximum row count void setMaximumRowCount(int

del void setModal(ComboBoxModel

ected index int getSelectedIndex()

ected Item Object getSelectedItem()

count int getItemCount()

derer void setRenderer(ListCellRe

itable void setEditable(boolean fl


tsents



Layout Managers

• Handle problems caused by:• GUI resizing by user• Operating system differences in fon• Locale-specific text layout requirem

• Layout manager classes:• BorderLayout

• FlowLayout

• BoxLayout

• CardLayout

• GridLayout

• GridBagLayout


er

Th nts in top,bot



The BorderLayout Manag

e BorderLayout manager places componetom, left, right and center locations.


12345678910111213141516



BorderLayoutExample

import java.awt.*;import javax.swing.*;

public class BorderExample { private JFrame f; private JButton bn, bs, bw, be, bc;

public BorderExample() { f = new JFrame("Border Layout"); bn = new JButton("Button 1"); bc = new JButton("Button 2"); bw = new JButton("Button 3"); bs = new JButton("Button 4"); be = new JButton("Button 5"); }


17181920212223242526272829303132



BorderLayoutExample

public void launchFrame() { f.add(bn, BorderLayout.NORTH); f.add(bs, BorderLayout.SOUTH); f.add(bw, BorderLayout.WEST); f.add(be, BorderLayout.EAST); f.add(bc, BorderLayout.CENTER); f.setSize(400,200); f.setVisible(true); }

public static void main(String args[]) { BorderExample guiWindow2 = new BorderExample(); guiWindow2.launchFrame(); }}


r

Th in a row, and ifthe xt row.



The FlowLayout Manage

e FlowLayoutmanager places components row fills, components are placed in the ne


12345678910111213141516171819



FlowLayoutExample

import javax.swing.*;import java.awt.*;

public class LayoutExample {private JFrame f;private JButton b1;private JButton b2;private JButton b3;private JButton b4;private JButton b5;

public LayoutExample() {f = new JFrame("GUI example");b1 = new JButton("Button 1");b2 = new JButton("Button 2");b3 = new JButton("Button 3");b4 = new JButton("Button 4");b5 = new JButton("Button 5");

}


2021222324252627282930313233 ();34353637



FlowLayoutExample

public void launchFrame() {f.setLayout(new FlowLayout());f.add(b1);f.add(b2);f.add(b3);f.add(b4);f.add(b5);f.pack();f.setVisible(true);

}

public static void main(String args[]) {LayoutExample guiWindow = new LayoutExampleguiWindow.launchFrame();

}

} // end of LayoutExample class


Th om left to right,and mn.



The BoxLayoutManager

e BoxLayoutmanager adds components fr from top to bottom in a single row of colu


r

Th ents in differentcar o box.



The CardLayoutManage

e CardLayoutmanager places the componds. Cards are usually controlled by a comb


r

Th in rows andcol



The GridLayoutManage

e GridLayout manager places componentsumns in the form of a grid.


12345678910111213141516



GridLayoutExample

import java.awt.*;import javax.swing.*;

public class GridExample { private JFrame f; private JButton b1, b2, b3, b4, b5;

public GridExample() { f = new JFrame("Grid Example"); b1 = new JButton("Button 1"); b2 = new JButton("Button 2"); b3 = new JButton("Button 3"); b4 = new JButton("Button 4"); b5 = new JButton("Button 5"); }


171819202122232425262728293031323334



GridLayoutExample

public void launchFrame() { f.setLayout (new GridLayout(3,2));

f.add(b1); f.add(b2); f.add(b3); f.add(b4); f.add(b5);

f.pack(); f.setVisible(true); }

public static void main(String args[]) { GridExample grid = new GridExample(); grid.launchFrame(); }}


er

Th onents in rowsand vides a widevar thecom



The GridBagLayoutManag

e GridBagLayout manager arranges comp columns, similar to a grid layout, but proiety of options for resizing and positioningponents.




GUI Construction

• Programmatic• GUI builder tool


n

1234 );56 IT_ON_CLOSE);78910111213



Programmatic Constructio

import javax.swing.*;public class HelloWorldSwing { private static void createAndShowGUI() { JFrame frame = new JFrame("HelloWorldSwing"

//Set up the window. frame.setDefaultCloseOperation(JFrame.EX JLabel label = new JLabel("Hello World");

// Add Label frame.add(label); frame.setSize(300,200);

// Display Window frame.setVisible(true);}


n

1415 new Runnable() {16 read:1718192021




public static void main(String[] args) {javax.swing.SwingUtilities.invokeLater(

//Schedule for the event-dispatching th //creating,showing this app's GUI.

public void run() {createAndShowGUI();} });

}}


n

Th




e output generated from the program


Me g JLabel:

XIT_ON_CLOSE)close button is

e visible.ntent pane not



Key Methods

thods for setting up the JFrame and addin

• setDefaultCloseOperationJFrame.E–Creates the program to exit when the clicked.

• setVisible(true)– Makes the JFram• add(label)– JLabel is added to the co

to the JFrame directly.


h as rendering

und) processes

Runnable())



Key Methods

• Tasks:• Executing GUI application code, suc• Handling GUI events• Handling time consuming (backgro

• The SwingUtilities class:• SwingUtilites.invokeLater(new

Sun

Java™ Programmi

H Events


ng Language

Module 13

andling GUI-Generated


ed an event

UIs ander class



Objectives

• Define events and event handling• Examine the Java SE event model• Describe GUI behavior• Determine the user action that originat• Develop event listeners• Describe concurrency in Swing-based G

describe the features of the SwingWork


penedents an event

ser’s interaction

vent e) {



What Is an Event?

• Events – Objects that describe what hap• Event sources – The generator of an ev• Event handlers – A method that receive

object, deciphers it, and processes the uJFrame

JPanel

JButton

The user clicks on the button

Some Event HandleractionPerformed(ActionE ...}

ActionEvent


ndlers.

ts when theyat component.

vent e) {

vent e) {



Delegation Model

• An event can be sent to many event ha

• Event handlers register with componenare interested in events generated by th

JFrame

JPanel

JButton

The user clicks on the button

Another Event Handler

One Event Handler

actionPerformed(ActionE ...}

actionPerformed(ActionE ...}ActionEvent


GUI

lers for the type

n one type of

ork among



Delegation Model

• Client objects (handlers) register with acomponent that they want to observe.

• GUI components trigger only the handof event that has occurred.

• Most components can trigger more thaevent.

• The delegation model distributes the wmultiple classes.


123456789101112131415161718



A Listener Example

import java.awt.*;import javax.swing.*;public class TestButton { private JFrame f; private JButton b;

public TestButton() { f = new JFrame("Test"); b = new JButton("Press Me!"); b.setActionCommand("ButtonPressed"); }

public void launchFrame() {b.addActionListener(new ButtonHandler());

f.add(b,BorderLayout.CENTER); f.pack(); f.setVisible(true); }


192021222324

Co wing:

123 tener {456789



A Listener Example

public static void main(String args[]) { TestButton guiApp = new TestButton(); guiApp.launchFrame(); }}

de for the event listener looks like the follo

import java.awt.event.*;

public class ButtonHandler implements ActionLis public void actionPerformed(ActionEvent e) { System.out.println("Action occurred"); System.out.println("Button’s command is: " + e.getActionCommand()); }}


java.util.EventObject

KeyEvent

MouseEvent



Event Categoriesjava.awt.AWTEvent ActionEvent

AdjustmentEvent

ComponentEvent

TextEvent

ContainerEvent

FocusEvent

InputEvent

WindowEvent

java.awt.event

ItemEvent


ces

Ca

Ac ActionEvent)

Item (ItemEvent)

Mo seEvent)useEvent)seEvent)eEvent)seEvent)

Momo

seEvent)Event)

Ke ent)vent)t)



Method Categories and Interfa

tegory Interface Name Methods

tion ActionListener actionPerformed(

ItemListener itemStateChanged

use MouseListener mousePressed(MoumouseReleased(MomouseEntered(MoumouseExited(MousmouseClicked(Mou

usetion

MouseMotionListener mouseDragged(MoumouseMoved(Mouse

y KeyListener keyPressed(KeyEvkeyReleased(KeyEkeyTyped(KeyEven


ces

Ca

Foc sEvent)vent)

Ad hanged)

Co omponentEvent)ComponentEvent)(ComponentEvent)omponentEvent)





us FocusListener focusGained(FocufocusLost(FocusE

justment AdjustmentListener adjustmentValueC(AdjustmentEvent

mponent ComponentListener componentMoved(CcomponentHidden(componentResizedcomponentShown(C


ces

Ca

Wi dowEvent)owEvent)indowEvent)(WindowEvent)owEvent)indowEvent)(WindowEvent)

Co ntainerEvent)

Wista

d(WindowEvent e)

Wifoc

(WindowEvent e)indowEvent e)





ndow WindowListener windowClosing(WinwindowOpened(WindwindowIconified(WwindowDeiconifiedwindowClosed(WindwindowActivated(WwindowDeactivated

ntainer ContainerListener componentAdded(CocomponentRemoved(ContainerEvent)

ndowte

WindowStateListener windowStateChange

ndowus

WindowFocusListener windowGainedFocuswindowLostFocus(W


ces

Ca

Mowh )

Inpme

ede)agede)

Hie

Hiebou

archyEvent e)erarchyEvent e)

AW TEvent e)

Tex extEvent)





useeel

MouseWheelListener mouseWheelMoved(MouseWheelEvent e

utthods

InputMethodListener caretPositionChang(InputMethodEvent inputMethodTextChn(InputMethodEvent

rarchy HierarchyListener hierarchyChanged(HierarchyEvent e)

rarchynds

HierarchyBoundsListener

ancestorMoved(HierancestorResized(Hi

T AWTEventListener eventDispatched(AW

t TextListener textValueChanged(T


12345 tener {6789101112



Complex Example

import java.awt.*;import java.awt.event.*;import javax.swing.*;public class TwoListener

implements MouseMotionListener, MouseLis private JFrame f; private JTextField tf;

public TwoListener() { f = new JFrame("Two listeners example"); tf = new JTextField(30); }


131415 ouse");16171819202122232425



Complex Example

public void launchFrame() { JLabel label = new JLabel("Click and drag the m // Add components to the frame f.add(label, BorderLayout.NORTH); f.add(tf, BorderLayout.SOUTH); // Add this object as a listener f.addMouseMotionListener(this); f.addMouseListener(this); // Size the frame and make it visible f.setSize(300, 200); f.setVisible(true); }


2627282930313233343536373839404142



Complex Example

// These are MouseMotionListener events public void mouseDragged(MouseEvent e) { String s = "Mouse dragging: X = " + e.getX() + " Y = " + e.getY(); tf.setText(s); }

public void mouseEntered(MouseEvent e) { String s = "The mouse entered"; tf.setText(s); }

public void mouseExited(MouseEvent e) { String s = "The mouse has left the building"; tf.setText(s); }


434445 he46474849505152535455565758



Complex Example

// Unused MouseMotionListener method. // All methods of a listener must be present in t // class even if they are not used. public void mouseMoved(MouseEvent e) { }

// Unused MouseListener methods. public void mousePressed(MouseEvent e) { } public void mouseClicked(MouseEvent e) { } public void mouseReleased(MouseEvent e) { }

public static void main(String args[]) { TwoListener two = new TwoListener(); two.launchFrame(); }}


of a program to

re called when



Multiple Listeners

• Multiple listeners cause unrelated partsreact to the same event.

• The handlers of all registered listeners athe event occurs.


extend adapterthat you need.

12345 {67891011121314



Event Adapters

• The listener classes that you define canclasses and override only the methods

• An example is:import java.awt.*;import java.awt.event.*;import javax.swing.*;

public class MouseClickHandler extends MouseAdapter

// We just need the mouseClick handler, so we use // an adapter to avoid having to write all the // event handler methods

public void mouseClicked(MouseEvent e) { // Do stuff with the mouse click... }}


sses

12345678910111213 apter {1415 )16171819



Event Handling Using Inner Cla

import java.awt.*;import java.awt.event.*;import javax.swing.*;public class TestInner { private JFrame f; private JTextField tf; // used by inner class

public TestInner() { f = new JFrame("Inner classes example"); tf = new JTextField(30); }

class MyMouseMotionListener extends MouseMotionAd public void mouseDragged(MouseEvent e) { String s = "Mouse dragging: X = "+ e.getX( + " Y = " + e.getY();

tf.setText(s); }}


sses

202122 ouse");2324252627 ner());2829303132333435363738



Event Handling Using Inner Cla

public void launchFrame() { JLabel label = new JLabel("Click and drag the m // Add components to the frame f.add(label, BorderLayout.NORTH); f.add(tf, BorderLayout.SOUTH); // Add a listener that uses an Inner class f.addMouseMotionListener(new MyMouseMotionListe f.addMouseListener(new MouseClickHandler()); // Size the frame and make it visible f.setSize(300, 200); f.setVisible(true); }

public static void main(String args[]) { TestInner obj = new TestInner(); obj.launchFrame(); }}


E Classes

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vent Handling Using Anonymous

import java.awt.*;import java.awt.event.*;import javax.swing.*;

public class TestAnonymous { private JFrame f; private JTextField tf;

public TestAnonymous() { f = new JFrame("Anonymous classes example"); tf = new JTextField(30); }

public static void main(String args[]) { TestAnonymous obj = new TestAnonymous(); obj.launchFrame(); }


E Classes

1920 ouse");2122232425 () {2627 )2829303132 Not shown3334353637



vent Handling Using Anonymous

public void launchFrame() { JLabel label = new JLabel("Click and drag the m // Add components to the frame f.add(label, BorderLayout.NORTH); f.add(tf, BorderLayout.SOUTH); // Add a listener that uses an anonymous class f.addMouseMotionListener(new MouseMotionAdapter public void mouseDragged(MouseEvent e) { String s = "Mouse dragging: X = "+ e.getX( + " Y = " + e.getY(); tf.setText(s); } }); // <- note the closing parenthesis f.addMouseListener(new MouseClickHandler()); // // Size the frame and make it visible f.setSize(300, 200); f.setVisible(true); }}


To m needsdif

hreads)UI (event

e time

Eac an instance ofjav



Concurrency In Swing

handle a GUI efficiently, the Swing prograferent threads to:

• Execute the application code (current t• Handle the events that arise from the G

dispatch threads)• Handle background tasks that might b

consuming (worker threads)

h task in a worker thread is represented byax.swing.SwingWorker.


Th e the followingreq

nation betweenther threads:

results:



The SwingWorkerClass

e SwingWorker class has methods to servicuirements:

• To provide communication and coordiworker thread tasks and the tasks on o• Properties: state and progress

• To execute simple background tasks:• doInBackground method

• To execute tasks that have intermediate• publish method

• To cancel the background threads:• cancel method

Sun

Java™ Programmi

ns


ng Language

Module 14

GUI-Based Applicatio


menu, and

d font of a



Objectives

• Describe how to construct a menu bar, menu items in a Java GUI

• Understand how to change the color ancomponent


I for bothut. However,

ich GUIs can becomponents

UI frame?



Relevance

• You now know how to set up a Java GUgraphic output and interactive user inponly a few of the components from whbuilt have been described. What other would be useful in a GUI?

• How can you create a menu for your G


to a menu

add them to

, and add them



How to Create a Menu

1. Create a JMenuBar object, and set it incontainer, such as a JFrame.

2. Create one or more JMenu objects, andthe menu bar object.

3. Create one or more JMenuItem objectsto the menu object.


123



Creating a JMenuBar

f = new JFrame("MenuBar");mb = new JMenuBar();f.setJMenuBar(mb);


131415161718192021



Creating a JMenu

f = new JFrame("Menu");mb = new JMenuBar();m1 = new JMenu("File");m2 = new JMenu("Edit");m3 = new JMenu("Help");mb.add(m1);mb.add(m2);mb.add(m3);f.setJMenuBar(mb);




Creating a JMenu


28293031323334353637383940



Creating a JMenuItem

mi1 = new JMenuItem("New");mi2 = new JMenuItem("Save");mi3 = new JMenuItem("Load");mi4 = new JMenuItem("Quit");mi1.addActionListener(this);mi2.addActionListener(this);mi3.addActionListener(this);mi4.addActionListener(this);m1.add(mi1);m1.add(mi2);m1.add(mi3);m1.addSeparator();m1.add(mi4);




Creating a JMenuItem


tem

192021222324252627....434445



Creating a JCheckBoxMenuI

f = new JFrame("CheckboxMenuItem");mb = new JMenuBar();m1 = new JMenu("File");m2 = new JMenu("Edit");m3 = new JMenu("Help");mb.add(m1);mb.add(m2);mb.add(m3);f.setJMenuBar(mb);.......mi5 = new JCheckBoxMenuItem("Persistent");mi5.addItemListener(this);m1.add(mi5);


tem



Creating a JCheckBoxMenuI


Co I include:



Controlling Visual Aspects

mmands to control visual aspects of the GU

• Colors:setForeground()setBackground()

• Example:Color purple = new Color(255, 0, 255);JButton b = new JButton(“Purple”);b.setBackground(purple);

Sun

Java™ Programmi


ng Language

Module 15

Threads


ology program,sed by that

rite platform-

when multiple

etween threads corruption



Objectives

• Define a thread• Create separate threads in a Java techn

controlling the code and data that are uthread

• Control the execution of a thread and windependent code with threads

• Describe the difficulties that might arisethreads share data

• Use waitand notify to communicate b• Use synchronized to protect data from


Ho le taskscon



Relevance

w do you get programs to perform multipcurrently?




Threads

• What are threads?Threads are a virtual CPU.

• The three parts of at thread are:• CPU• Code• Data

CPU

Code Data

A thread orexecution context


12345678910111213141516171819



Creating the Thread

public class ThreadTester { public static void main(String args[]) { HelloRunner r = new HelloRunner(); Thread t = new Thread(r); t.start(); }}class HelloRunner implements Runnable { int i; public void run() { i = 0; while (true) { System.out.println("Hello " + i++); if ( i == 50 ) { break; } } }}


characteristics:ble instance.e.

”nner



Creating the Thread

• Multithreaded programming has these• Multiple threads are from one Runna• Threads share the same data and cod

• For example:Thread t1 = new Thread(r);Thread t2 = new Thread(r);

CPU

Code DataHelloRunner Instance “r

Thread t}New Thread

Class of HelloRu




Starting the Thread

• Use the start method.• Place the thread in a runnable state.


N Dead

run() Completes



Thread Scheduling

Runnable

ew

RunningScheduler

Blocked

Unblocked Event Blocked

start()


le

123456789101112131415



Thread Scheduling Examp

public class Runner implements Runnable { public void run() { while (true) { // do lots of interesting stuff

// ...// Give other threads a chance

try {Thread.sleep(10);

} catch (InterruptedException e) { // This thread’s sleep was interrupted // by another thread } } }}


1234567891011121314



Terminating a Thread

public class Runner implements Runnable { private boolean timeToQuit=false;

public void run() { while ( ! timeToQuit ) { // continue doing work } // clean up before run() ends }

public void stopRunning() { timeToQuit=true; }}


12345678910111213



Terminating a Thread

public class ThreadController { private Runner r = new Runner(); private Thread t = new Thread(r);

public void startThread() { t.start(); }

public void stopThread() { // use specific instance of Runner r.stopRunning(); }}




Basic Control of Threads

• Test threads:isAlive()

• Access thread priority:getPriority()setPriority()

• Put threads on hold:Thread.sleep() // static methodjoin()Thread.yield() // static method


12345 a while678910111213141516



The joinMethod

public static void main(String[] args) { Thread t = new Thread(new Runner()); t.start(); ... // Do stuff in parallel with the other thread for ... // Wait here for the other thread to finish try { t.join(); } catch (InterruptedException e) { // the other thread came back early } ... // Now continue in this thread ...}


ds

1234567891011121314151617



Other Ways to Create Threa

public class MyThread extends Thread { public void run() { while ( true ) { // do lots of interesting stuff try { Thread.sleep(100); } catch (InterruptedException e) { // sleep interrupted } } }

public static void main(String args[]) { Thread t = new MyThread(); t.start(); }}


eads



Selecting a Way to Create Thr

• Implement Runnable:• Better object-oriented design• Single inheritance• Consistency

• Extend Thread:Simpler code


ord

123456789101112131415



Using the synchronizedKeyw

public class MyStack {

int idx = 0; char [] data = new char[6];

public void push(char c) { data[idx] = c; idx++; }

public char pop() { idx--; return data[idx]; }}


lock flag. with the lock

h(char c) {(this) { c;

onized(this)



The Object Lock Flag

• Every object has a flag that is a type of• The synchronized enables interaction

flag.

Object this

public void pussynchronized data[idx] =idx++;

}}

Thread before synchr

Code orBehavior

Data orState


h(char c) {(this) { c;

nized(this)




Object this

public void pussynchronized data[idx] =idx++;

}}

Thread after synchro

Code orBehavior

Data orState


op() {d (this) {

ta[idx];

ing tozed(this)




Object this

public char psynchronizeidx--;return da

}}

Another thread, try

Waiting for

lock flag missing

object lock

Code orBehavior

Data orState

execute synchroni


Th ts:

d of the

eturn, ored code block



Releasing the Lock Flag

e lock flag is released in the following even

• Released when the thread passes the ensynchronized code block

• Released automatically when a break, rexception is thrown by the synchroniz


U ogether

nchronized.ed should be



sing synchronized– Putting It T

• All access to delicate data should be sy• Delicate data protected by synchroniz

private.


U ogether

Th ent:

publ sy }}

publ//

}



sing synchronized– Putting It T

e following two code segments are equival

ic void push(char c) {nchronized(this) {// The push method code

ic synchronized void push(char c) { The push method code


h



Thread State Diagram Wit


N Dead

run() Completes



Synchronization

Blocked inObject’s

Lock Pool

Runnable

ew

RunningScheduler

Blocked


Lock Acquired Synchronized

start()


A d

from the other.

s



Deadlock

eadlock has the following characteristics:

• It is two threads, each waiting for a lock• It is not detected or avoided.• Deadlock can be avoided by:

• Deciding on the order to obtain lock• Adhering to this order throughout• Releasing locks in reverse order


otify

two threads.

at your

stination and

pon arrival at



Thread Interaction – waitand n

• Scenario:Consider yourself and a cab driver as

• The problem:How do you determine when you aredestination?

• The solution:• You notify the cab driver of your de

relax.• The driver drives and notifies you u

your destination.


Th



Thread Interaction

read interactions include:

• The wait and notify methods• The pools:

• Wait pool• Lock pool


h



Thread State Diagram Wit


Blocked inObject’s

Wait Pool

New Dead

un() Completes

)

wait()[Must have lock]/Releases lock

st



wait and notify

notify() orBlocked inObject’s

Lock Pool

Runnable RunningScheduler

Blocked


r

Lock Acquired Synchronized

interrupt(

art()


tion

notifications in



Monitor Model for Synchroniza

• Leave shared data in a consistent state.• Ensure programs cannot deadlock.• Do not put threads expecting different

the same wait pool.


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The ProducerClass

package mod13;

public class Producer implements Runnable { private SyncStack theStack; private int num; private static int counter = 1;

public Producer (SyncStack s) { theStack = s; num = counter++; }


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The ProducerClass

public void run() { char c;

for (int i = 0; i < 200; i++) { c = (char)(Math.random() * 26 +’A’); theStack.push(c); System.out.println(“Producer” + num + “: “ + try { Thread.sleep((int)(Math.random() * 300)); } catch (InterruptedException e) { // ignore it } } } // END run method

} // END Producer class


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The ConsumerClass

package mod13;

public class Consumer implements Runnable { private SyncStack theStack; private int num; private static int counter = 1;

public Consumer (SyncStack s) { theStack = s; num = counter++; }


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The ConsumerClass

public void run() { char c; for (int i = 0; i < 200; i++) { c = theStack.pop(); System.out.println(“Consumer” + num + “: “ +

try { Thread.sleep((int)(Math.random() * 300)); } catch (InterruptedException e) { // ignore it } } } // END run method


Th

publ

pr ter>(400);

pu

}

pu

}}



The SyncStackClass

is is a sketch of the SyncStack class:

ic class SyncStack {

ivate List<Character> buffer = new ArrayList<Charac

blic synchronized char pop() {// pop code here

blic synchronized void push(char c) {// push code here


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The popMethod

public synchronized char pop() { char c; while (buffer.size() == 0) { try { this.wait(); } catch (InterruptedException e) { // ignore it... } } c = buffer.remove(buffer.size()-1); return c; }


22232425



The pushMethod

public synchronized void push(char c) { this.notify(); buffer.add(c); }


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The SyncTestClass

package mod13;public class SyncTest { public static void main(String[] args) { SyncStack stack = new SyncStack(); Producer p1 = new Producer(stack); Thread prodT1 = new Thread (p1); prodT1.start(); Producer p2 = new Producer(stack); Thread prodT2 = new Thread (p2); prodT2.start();

Consumer c1 = new Consumer(stack); Thread consT1 = new Thread (c1); consT1.start(); Consumer c2 = new Consumer(stack); Thread consT2 = new Thread (c2); consT2.start(); }}


ProdConsProdConsProdProdProdConsConsProdProdConsConsProdConsProdConsCons



The SyncTestClass

ucer2: Fumer1: Fucer2: Kumer2: Kucer2: Tucer1: Nucer1: Vumer2: Vumer1: Nucer2: Vucer2: Uumer2: Uumer2: Vucer1: Fumer1: Fucer2: Mumer2: Mumer2: T

Sun

Java™ Programmi


ng Language

Module 16

Networking


nection

forservers



Objectives

• Develop code to set up the network con• Understand the TCP/IP Protocol• Use ServerSocket and Socket classes

implementation of TCP/IP clients and


Ho nt machine anda s



Relevance

w can a communication link between a clieerver on the network be established?


Th

So

am and an

ams.

Se

Set telephonesys ch must belist



Networking

is section describes networking concepts.

ckets

• Sockets hold two streams: an input streoutput stream.

• Each end of the socket has a pair of stre

tting Up the Connection

up of a network connection is similar to a tem: One end must dial the other end, whiening.


o.com



Networking

client.bar.com

client.baz.com

server.fo

18000

18002

3000


logy

following:hinese at the server



Networking With Java Techno

• To address the connection, include the • The address or name of remote mac• A port number to identify the purpo

• Port numbers range from 0–65535.


#)

)



Java Networking Model

Server

ServerSocket (port #)

OutputStream

InputStream

Socket.close()

Client

Socket (host, port

OutputStream

InputStream

Socket.close(

Register withthis service

Wait for aconnection

(Attempt to connect)Socket()

ServerSocket.accept()


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Minimal TCP/IP Server

import java.net.*;import java.io.*;

public class SimpleServer { public static void main(String args[]) { ServerSocket s = null;

// Register your service on port 5432 try {

s = new ServerSocket(5432); } catch (IOException e) { e.printStackTrace(); }


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// Run the listen/accept loop forever while (true) { try { // Wait here and listen for a connection

Socket s1 = s.accept();

// Get output stream associated with the so OutputStream s1out = s1.getOutputStream( BufferedWriter bw = new BufferedWriter( new OutputStreamWriter(s1out));

// Send your string! bw.write(“Hello Net World!\n”);


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// Close the connection, but not the serverbw.close();s1.close();

} catch (IOException e) { e.printStackTrace(); } // END of try-catch

} // END of while(true)

} // END of main method

} // END of SimpleServer program


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Minimal TCP/IP Client

import java.net.*;import java.io.*;

public class SimpleClient {

public static void main(String args[]) {

try { // Open your connection to a server, at port // localhost used here

Socket s1 = new Socket("127.0.0.1", 5432)

// Get an input stream from the socket InputStream is = s1.getInputStream(); // Decorate it with a "data" input stream DataInputStream dis = new DataInputStream(is)


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Minimal TCP/IP Client

// Read the input and print it to the screen System.out.println(dis.readUTF());

// When done, just close the steam and connec dis.close(); s1.close();

} catch (ConnectException connExc) { System.err.println("Could not connect.");

} catch (IOException e) { // ignore } // END of try-catch

} // END of main method

} // END of SimpleClient program

Java must read for everyone

Engineering

Transcript of Java must read for everyone