Computer Programming with JAVA

Computer Programming with JAVA

Chapter 1Introduction and A Taste of Java

Computer Programming with Java

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Contents

Object-Oriented Programming History of the Java Language A First Java Program Compiling and Running a Java Program


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Object-Oriented Programming

What are Objects? All things around us

• Ability to perform actions• Status

OOP (or Paradigm) A programming methodology (paradigm) that

views a program as this sort of world consisting of objects that interact with each other by means of actions.

Methods, data


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Object-Oriented Programming (1)

Objects• A program construction that has data associated with it

and that can perform certain actions Methods

• The actions performed by objects Class

• A type or kind of object

What is difference between OOP and Procedural-Oriented Programming? Code reusability Efficiency


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A Brief History of the Java Language

A brief history of the Java 1990:

• Gosling, J. and Naughton, P. 1991: Green Project

• *7 system by 1st Person Inc. named by Oak• Research settop box and VOD with Green (O.S.) • Gosling, J., designing a programming language for

home appliances• Java byte code: Intermediate language for

inexpensive portability 1991: WWW, 1992: Web browser


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A Brief History of the Java Language (1)

1994: • NCSA Mosaic, WebRunner (HotJava) browser, applet

1995: • adapted for New technology for WWW• Netscape and MS agreed license of Java

1996: • Java 1.0.2


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A Taste of Java

Features JAVA : A simple, Object-Oriented, distributed, interpreted,

robust, secure, machine-independent (portable), high-performance, multi-thread, and dynamic language

• Simple : No operator overloading, multiple inheritance, memory management, header file, structure, union, enumeration, pointer arithmetic, template, preprocessing, user-defined type conversion.

• Object-Oriented• Distributed : WWW• Robust : no memory management, exception

handling, error checking in compile-time.


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A Taste of Java (1)• secure : public-key, restricted client resource

access• 자바 애플릿은 클라이언트 내의 디스크를 read/write 할 수 없다 .• 자바 애플릿은 클라이언트의 다른 응용프로그램을 실행시킬 수 없다 .• 자바 애플릿은 다운로드된 서버 외에는 접속할 수 없다 .

• Machine-Independent (portable)• “Write Once Run Everywhere”

• Compiled : compiled into byte code• Interpreted : bytecodes are interpreted by Java

Virtual Machine• Multi-Thread


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Java Compiler

Applet Store

Java AppletBytecode verifier

Class loader

Java Run-time interpreter

Just-in-Time

Compiler

Hardware platform

Java Bytecodes Java

Bytecodes

Server Client

Security model in Java


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Sourcecode

Pentium

Mac

Unix

Pentiumexecutable

code

Macexecutable

code

Unixexecutable

Sourcecode

Pentium

Mac

Unix

PentiumJava Interpreter

MacJava Interpreter

UnixJava Interpreter

JavaBytecodes

Machine-independent Property


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A Taste of Java (2)

Types of Java program Applet

• To be sent to another (remote) location on the WWW and run there.

Application• Running on your (local) computer. main()

Byte Code Executable code in the Java Machine-independent, neutral, intermediate

code


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A Taste of Java (3)

Difference between C++ and Java

J ava C++Inheritance Single Multiple

Garbage Collection Automatic ManualOperator overloading o

String Built-in class Character arrayType conversion Automatic Manual


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Java Development Kit JDK

contains the software and tools that developers need to compile, debug, and run applets and applications written using the Java programming language.

JDK 1.0 Just reflect the feature of language itself and

the one of Applet Sun didn’t pass through the alpha, beta version, and

just were intended on displaying the bug-modified version

problem : huge bugs and insufficient GUI


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Java Development Kit (1)

JDK 1.1 Event-driven model, light component

framework JDBC, RMI, JavaBeans, Globalization, Localization API Object Serialization Servlet Api, Enterprise JavaBeans 자바가 Server 측에 수용되는데 밑거름이 됨


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Java Development Kit (2)

JDK 1.2 JDBC, RMI 등의 기반 API 들을 개선 2-Dimension Imagiing 과 Printing, GUI

component Security Model CORBA 의 지원 (org.*) 주로 client 측의 S/W 를 위한 API 완성


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Java Development Kit (3) Java 2 Platform

Java 1.2 의 정식 버젼 API 관련

• Swing, 2D API, drag&drop API, JFC

Security 관련• Policy-Based Access Control

프로그래밍 관련• 강력한 자료구조코딩을 위한 collection framework• 참조객체지원• Reflection 과 Serialization 에 대한 성능 개선

HotSpot 은 포함되지 않음


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

System.out.println("Hello out there.");System.out.println("Want to talk some more?");System.out.println("Answer y for yes or n for no.");

char answerLetter;answerLetter = SavitchIn.readLineNonwhiteChar();if(answerLetter == 'y')

System.out.println("Nice weather we are having.");

System.out.println("Good-bye");

System.out.println("Press enter key to end program.");String junk;junk = SavitchIn.readLine();

}}

Display 1.4: A Simple Java Program


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Spelling Rules Identifier

A name in a programming language• e.g.) a class or variable name

Rules It must consist entirely of letters, digits (0-9), and

underscore character (_) The first character cannot be a digit No identifier can contain a space or any other character

such as a period or an *. There is no limit to the length of a name Case-Sensitive

• e.g.) mystuff, myStuff, Mystuff


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Spelling Rules (1) Unicode

• It can include characters that are used in other languages

It must avoid the reserved words (or keywords) and built-in classes and their member


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Compiling and Running a Java Program

Compiling javac MyClass.java

Running java MyClass


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Display 1.3: Compiling and Running a Java Program

Java source (.java)(FirstProgram.java)

Java Compiler(javac)

Java Bytecodes (FirstProgram.class)

Java Interpreter(java)

Computer Programming with JAVA

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