Intro to Java

Java ApplicationsSwing Class

Graphics

Java Outline

• Today– Intro and Applications– GUI

• Client / Server • RMI, JDBC

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JAVA Implementation

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Java program

Java program

VM

Java Cmds

Java program

VM

Java Cmds

Java program

VM

Java Cmds

SPARC PowerPC Intel

Operations Environments

• Applications program (~DOS window)– supports file access

• Applet (browser) – no longer generally supported– supports Internet linkages.

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Building Java Applications Using Java Development Kit

• Get a copy of the JDK (www.oracle.com, etc.)• Install the development kit (tools and classes)• Create MyApp.java source file– text editor (notepad, etc.)– winedit, Café, etc.

• Compile .java file to create .class file– javac MyApp.java

• Run application (.class file) through java VM– java MyApp

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Building Java Applications Using Java IDEs

• NetBeans– Available from netbeans.org

• Eclipse– Available from www.eclipse.org

• jCreator le– available from jcreator.com– jcreator pro – academic license $35

• jDeveloper– available from www.oracle.com/technetwork/developer-

tools/jdev• many others

Sample Java App

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G:\Data\Java\MyHelloApp>type MyHelloApp.javaclass MyHelloApp { public static void main (String argv[]) { String message[] = new String[2]; message[0] = "Welcome to CS423"; message[1] = "The subject is JAVA!";

System.out.println (message[0]); System.out.println (message[1]); } }

MyHelloApp Implementation

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MyHelloApp.java

MyHelloApp.class

VM

machine code

MyHelloApp.class

Java compiler

Java byte code

Sample Java App

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G:\Data\Java\MyHelloApp>javac MyHelloApp.java

G:\Data\Java\MyHelloApp>java MyHelloAppWelcome to CS423The subject is JAVA!

G:\Data\Java\MyHelloApp>

MyHelloApp.class

Get Input from User

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import java.io.*;

class InputApp { InputApp () { DataInputStream dis = new DataInputStream (System.in); String sIn = " "; String sOut = " "; File fIn; File fOut; FileInputStream fis; FileOutputStream fos; int iNumBytesRead; byte[] ab;

Get Input from User

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System.out.println ("*-------------------------------------------*"); System.out.print ("Enter Source File Name Here: "); System.out.flush (); try {sIn = dis.readLine ();} catch (Exception e) {System.out.println ("Exception on input file name"

+ e);} System.out.print("Enter Destination File Name Here: "); System.out.flush (); try {sOut = dis.readLine ();} catch (Exception e) {System.out.println ("Exception on output file name"

+ e);}

Get Input from User

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try { fIn = new File (sIn); fis = new FileInputStream (fIn); fOut = new File (sOut); fos = new FileOutputStream (fOut); ab = new byte[2048]; while ((iNumBytesRead = fis.read (ab)) != -1) { fos.write (ab, 0, iNumBytesRead); } fis.close (); fos.close (); }catch (Exception e) {System.out.println ("Exception during copy: " + e); }

Get Input from User

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System.out.println ("Data copied from " + sIn + " to "+ sOut);

System.out.println ("*-------------------------------------------*");

}

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

Get Input from User

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G:\Data\Java\InputApp>java InputApp*-------------------------------------------*Enter Source File Name Here: books_db.txtEnter Destination File Name Here: My_list.txtData copied from books_db.txt to My_list.txt*-------------------------------------------*

G:\Data\Java\InputApp>

Swing Components

• Defined in package javax.swing– Pure Java components

• AWT components tied to local platform GUI– UNIX java windows look like X windows– Windows java windows look like Windows

windows (??)– etc.

• Swing defines a common look and feel for Java.

Product.java

// From Java: How to Program - Deitel and Deitel// Calculate the product of three integersimport javax.swing.JOptionPane;public class Product { public static void main( String args[] ) { int x, y, z, result; String xVal, yVal, zVal; xVal = JOptionPane.showInputDialog( "Enter first integer:" ); yVal = JOptionPane.showInputDialog( "Enter second integer:" ); zVal = JOptionPane.showInputDialog( "Enter third integer:" );

Product.java

x = Integer.parseInt( xVal );

y = Integer.parseInt( yVal );

z = Integer.parseInt( zVal );

result = x * y * z;

JOptionPane.showMessageDialog( null,

"The product is " + result );

System.exit( 0 );

}

}

Product Output(s)

JOptionPane

• Similar to windows message boxes• Types of Option Panes:

showConfirmDialog(null,message,title,optionType,msgType);

Asks a confirming question, like yes/no/cancel.

showInputDialog(message);

Prompt for some input.

showMessageDialog(null, message);

Tell the user about something that has happened.

showOptionDialog(....);

The Grand Unification of the above three.

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Additional Swing Options

JOptionPane.showMessageDialog(null, "This is an alert", "Alert", JOptionPane.ERROR_MESSAGE);

JOptionPane.showConfirmDialog(null,

"Is that your final answer?", "Choice Dialog",

JOptionPane.YES_NO_OPTION);

Additional Swing Options Object[] options = { "Lady", "Tiger" };

choice = JOptionPane.showOptionDialog(null,

"What will it be -\nThe Lady or the Tiger?", "Decision",

JOptionPane.DEFAULT_OPTION, JOptionPane.QUESTION_MESSAGE,

null, options, options[0]);

if (choice == 0)

JOptionPane.showMessageDialog( null, "You chose the Lady", "Result", JOptionPane.PLAIN_MESSAGE );

else

JOptionPane.showMessageDialog( null, "You chose the Tiger", "Result", JOptionPane.PLAIN_MESSAGE );

Additional Swing Options

Object[] possibleValues = { "First", "Second", "Third" };

Object selectedValue = JOptionPane.showInputDialog(null,

"Choose one", "Input", JOptionPane.INFORMATION_MESSAGE, null, possibleValues, possibleValues[0]);

Graphics in Applications

• Must include a main() method• Must extend the AWT Frame class, or swing JFrame class

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HelloWorldWindow

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import java.awt.*;import java.awt.event.*;

public class HelloWorldWindow implements WindowListener{ public HelloWorldWindow() { myFrame f=new myFrame(); f.addWindowListener (this);

} public void windowClosing(WindowEvent e) { System.out.println ("Closing Window"); System.exit(0); }

HelloWorldWindowclass myFrame extends Frame{ myFrame() { this.setSize(300, 200); this.show(); } public void paint(Graphics g) { String str = "A Windows version of Hello,

World"; g.drawString(str, 25, 75); }

public static void main(String[] args) { Frame f = new HelloWorldWindow();

f.resize(300, 200); f.show();

}}

}

HelloWorldWindow Output

public void paint (Graphics g)

• Provides an initial presentation of Graphics• Works on Graphics object – (like device context).– Place to store settings for screen output (text,

images. etc.)

• Must be regenerated following changes.

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Event Driven Programming

• Operating System recognizes an event• Sends a signal to appropriate object• Object receives event notification and calls

appropriate function

public void windowClosing(WindowEvent e) { System.out.println ("Closing Window"); System.exit(0); }

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Object Layout

• BorderLayout (default for Frames)• FlowLayout (default for Panels)• GridLayout• GridbagLayout• CardLayout• Fixed:– object.reshape (x, y, width, height);

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nuTextTest Example

Linux

Windows

NuTextTest2.java

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

public class NuTextTest2 extends JFrame { public NuTextTest2() { setTitle("NuTextTest2"); Container p = getContentPane();; p.setLayout(new FlowLayout()); TickButton = new Button("Tick"); p.add(TickButton); TickButton.addActionListener(

new ActionListener() { public void actionPerformed (ActionEvent e) { int minutes = Integer.parseInt(minuteField.getText()); minutes += 1; String min = String.valueOf(minutes); minuteField.setText(min); } } //end of ActionListener ); //end of TickButton

NuTextTest2.java

SetTime = new Button("Set Time"); p.add(SetTime); SetTime.addActionListener( new ActionListener() { public void actionPerformed (ActionEvent e) {

String tim = hourField.getText()+ ":" + minuteField.getText(); timeField.setText(tim); } } );

NuTextTest2.java

hourField = new TextField("12", 3); p.add(hourField); minuteField = new TextField("00", 3); p.add(minuteField); timeField = new TextField("", 12); p.add(timeField);

setSize (400,100); show (); }//end of NuTextTest2 (constructor)

private TextField hourField; private TextField minuteField; private TextField timeField; private Button TickButton; private Button SetTime;

NuTextTest2.java

public static void main(String[] args) {

NuTextTest2 app = new NuTextTest2(); app.addWindowListener( new WindowAdapter() { public void windowClosing( WindowEvent e ) { System.exit( 0 ); } } ); }//end of main()}//end of program

Summary

• Java is:– Platform independent– Object-oriented– Dynamic– Flexible – used in many different domains– Command line or graphical