import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.net.*;

/** Applet reads arrays of strings packaged inside
 *  a QueryCollection and places them in a scrolling
 *  TextArea. The QueryCollection obtains the strings
 *  by means of a serialized object input stream
 *  connected to the QueryGenerator servlet.
 *  


 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
  *  May be freely used or adapted.
 */

public class ShowQueries extends Applet
                         implements ActionListener, Runnable {
  private TextArea queryArea;
  private Button startButton, stopButton, clearButton;
  private QueryCollection currentQueries;
  private QueryCollection nextQueries;
  private boolean isRunning = false;
  private String address =
    "/servlet/cwp.QueryGenerator";
  private URL currentPage;
  
  public void init() {
    setBackground(Color.white);
    setLayout(new BorderLayout());
    queryArea = new TextArea();
    queryArea.setFont(new Font("Serif", Font.PLAIN, 14));
    add(queryArea, BorderLayout.CENTER);
    Panel buttonPanel = new Panel();
    Font buttonFont = new Font("SansSerif", Font.BOLD, 16);
    startButton = new Button("Start");
    startButton.setFont(buttonFont);
    startButton.addActionListener(this);
    buttonPanel.add(startButton);
    stopButton = new Button("Stop");
    stopButton.setFont(buttonFont);
    stopButton.addActionListener(this);
    buttonPanel.add(stopButton);
    clearButton = new Button("Clear TextArea");
    clearButton.setFont(buttonFont);
    clearButton.addActionListener(this);
    buttonPanel.add(clearButton);
    add(buttonPanel, BorderLayout.SOUTH);
    currentPage = getCodeBase();
    // Request a set of sample queries. They
    // are loaded in a background thread, and
    // the applet checks to see if they have finished
    // loading before trying to extract the strings.
    currentQueries = new QueryCollection(address, currentPage);
    nextQueries = new QueryCollection(address, currentPage);
  }

  /** If you press the "Start" button, the system
   *  starts a background thread that displays
   *  the queries in the TextArea. Pressing "Stop"
   *  halts the process, and "Clear" empties the
   *  TextArea.
   */
 
  public void actionPerformed(ActionEvent event) {
    if (event.getSource() == startButton) {
      if (!isRunning) {
        Thread queryDisplayer = new Thread(this);
        isRunning = true;
        queryArea.setText("");
        queryDisplayer.start();
        showStatus("Started display thread...");
      } else {
        showStatus("Display thread already running...");
      }
    } else if (event.getSource() == stopButton) {
      isRunning = false;
      showStatus("Stopped display thread...");
    } else if (event.getSource() == clearButton) {
      queryArea.setText("");
    }
  }

  /** The background thread takes the currentQueries
   *  object and every half-second places one of the queries
   *  the object holds into the bottom of the TextArea. When
   *  all of the queries have been shown, the thread copies
   *  the value of the nextQueries object into
   *  currentQueries, sends a new request to the server
   *  in order to repopulate nextQueries, and repeats
   *  the process.
   */

  public void run() {
    while(isRunning) {
      showQueries(currentQueries);
      currentQueries = nextQueries;
      nextQueries = new QueryCollection(address, currentPage);
    }
  }

  private void showQueries(QueryCollection queryEntry) {
    // If request has been sent to server but the result
    // isn't back yet, poll every second. This should
    // happen rarely but is possible with a slow network
    // connection or an overloaded server.
    while(!queryEntry.isDone()) {
      showStatus("Waiting for data from server...");
      pause(1);
    }
    showStatus("Received data from server...");
    String[] queries = queryEntry.getQueries();
    String linefeed = "\n";
    // Put a string into TextArea every half-second.
    for(int i=0; i
                                

FilterTag.java Custom tag that modifies the tag body

package cwp.tags;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
import cwp.*;

/** A tag that replaces <, >, ", and & with their HTML
 *  character entities (<, >, ", and &).
 *  After filtering, arbitrary strings can be placed
 *  in either the page body or in HTML attributes.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class FilterTag extends BodyTagSupport {
  public int doAfterBody() {
    BodyContent body = getBodyContent();
    String filteredBody =
      ServletUtilities.filter(body.getString());
    try {
      JspWriter out = body.getEnclosingWriter();
      out.print(filteredBody);
    } catch(IOException ioe) {
      System.out.println("Error in FilterTag: " + ioe);
    }
    // SKIP_BODY means we're done. If we wanted to evaluate
    // and handle the body again, we'd return EVAL_BODY_TAG.
    return(SKIP_BODY);
  }
}

Using Applets as Front Ends to Server-Side Programs
**************************************************
SearchApplet.java An applet that searches multiple search engines,
 displaying the results in side-by-side frame cells. Uses the following files: 
SearchSpec.javaParallelSearches.htmlSearchAppletFrame.htmlGoogleResultsFrame.htmlInfoseekResultsFrame.htmlLycosResultsFrame.html
***************************************************
//
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.net.*;
//

/** An applet that reads a value from a TextField,
 *  then uses it to build three distinct URLs with embedded
 *  GET data: one each for Google, Infoseek, and Lycos.
 *  The browser is directed to retrieve each of these
 *  URLs, displaying them in side-by-side frame cells.
 *  Note that standard HTML forms cannot automatically
 *  perform multiple submissions in this manner.
 *  


 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,

 *  May be freely used or adapted.
 */

public class SearchApplet extends Applet
                          implements ActionListener {
  private TextField queryField;
  private Button submitButton;

  public void init() {
    setBackground(Color.white);
    setFont(new Font("Serif", Font.BOLD, 18));
    add(new Label("Search String:"));
    queryField = new TextField(40);
    queryField.addActionListener(this);
    add(queryField);
    submitButton = new Button("Send to Search Engines");
    submitButton.addActionListener(this);
    add(submitButton);
  }

  /** Submit data when button is pressed or
   *  user presses Return in the TextField.
   */
  
  public void actionPerformed(ActionEvent event) {
    String query = URLEncoder.encode(queryField.getText());
    SearchSpec[] commonSpecs = SearchSpec.getCommonSpecs();
    // Omitting HotBot (last entry), as they use JavaScript to
    // pop result to top-level frame. Thus the length-1 below.
    for(int i=0; i
                                

import java.awt.*;

/** An example of translating and rotating the coordinate
 *  system before each drawing.
 *
 *******************************

public class RotationExample extends StrokeThicknessExample {
  private Color[] colors = { Color.white, Color.black };

  public void paintComponent(Graphics g) {
    clear(g);
    Graphics2D g2d = (Graphics2D)g;
    drawGradientCircle(g2d);
    drawThickCircleOutline(g2d);
    // Move the origin to the center of the circle.
    g2d.translate(185.0, 185.0);
    for (int i=0; i<16; i++) {
      // Rotate the coordinate system around current
      // origin, which is at the center of the circle.
      g2d.rotate(Math.PI/8.0);
      g2d.setPaint(colors[i%2]);
      g2d.drawString("Java", 0, 0);
    }
  }

public static void main(String[] args) {
    WindowUtilities.openInJFrame(new RotationExample(),
                                 380, 400);
  }
}

StrokeThicknessExample.java 
>>>>>>>>>>>>>>>>>>>>>>>>>>>
import java.awt.*;

/** An example of controlling the Stroke (pen) widths when
 *  drawing.
 *
 ******************
 */

public class StrokeThicknessExample extends FontExample {
  public void paintComponent(Graphics g) {
    clear(g);
    Graphics2D g2d = (Graphics2D)g;
    drawGradientCircle(g2d);
    drawBigString(g2d);
    drawThickCircleOutline(g2d);
  }

  protected void drawThickCircleOutline(Graphics2D g2d) {
    g2d.setPaint(Color.blue);
    g2d.setStroke(new BasicStroke(8)); // 8-pixel wide pen
    g2d.draw(getCircle());
  }

  public static void main(String[] args) {
    WindowUtilities.openInJFrame(new StrokeThicknessExample(),
                                 380, 400);
  }
}

ListFonts.java Lists all local fonts available for graphical drawing. 
***********************
import java.awt.*;

/** Lists the names of all available fonts. 
 *
 ******************

public class ListFonts {
  public static void main(String[] args) {
    GraphicsEnvironment env =
      GraphicsEnvironment.getLocalGraphicsEnvironment();
    String[] fontNames = env.getAvailableFontFamilyNames();
    System.out.println("Available Fonts:");
    for(int i=0; i>>>>>>>>>>>>>>>>>>>>>>>

~~~~~~~~~~~~~~~~~~~
TransparencyExample.java Illustrates the effect of different transparency (alpha) values when drawing a shape.
~~~~~~~~~~~~~~~~~~~
import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;

/** An illustration of the use of AlphaComposite to make
 *  partially transparent drawings.
 *
 **********************************

public class TransparencyExample extends JPanel {
  private static int gap=10, width=60, offset=20,
                     deltaX=gap+width+offset;
  private Rectangle
    blueSquare = new Rectangle(gap+offset, gap+offset, width,
                               width),
    redSquare = new Rectangle(gap, gap, width, width);

  private AlphaComposite makeComposite(float alpha) {
    int type = AlphaComposite.SRC_OVER;
    return(AlphaComposite.getInstance(type, alpha));
  }

  private void drawSquares(Graphics2D g2d, float alpha) {
    Composite originalComposite = g2d.getComposite();
    g2d.setPaint(Color.blue);
    g2d.fill(blueSquare);
    g2d.setComposite(makeComposite(alpha));
    g2d.setPaint(Color.red);
    g2d.fill(redSquare);
    g2d.setComposite(originalComposite);
  }

  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D)g;
    for(int i=0; i<11; i++) {
      drawSquares(g2d, i*0.1F);
      g2d.translate(deltaX, 0);
    }
  }

  public static void main(String[] args) {
    String title = "Transparency example: alpha of the top " +
                   "(red) square ranges from 0.0 at the left " +
                   "to 1.0 at the right. Bottom (blue) square " + 
                   "is opaque.";
    WindowUtilities.openInJFrame(new TransparencyExample(),
                                 11*deltaX + 2*gap,
                                 deltaX + 3*gap,
                                 title, Color.lightGray);
  }
}
>>>>>>>>>>>>>>>>>>

***********************************    
* ActionExample1.java Inherits from CloseableFrame.java and uses SetSizeButton.java.
    * ActionExample2.java Inherits from CloseableFrame.java.
    **********************************************************
ActionExample1.java
*******************
import java.awt.*;

public class ActionExample1 extends CloseableFrame {
  public static void main(String[] args) {
    new ActionExample1();
  }

  public ActionExample1() {
    super("Handling Events in Component");
    setLayout(new FlowLayout());
    setFont(new Font("Serif", Font.BOLD, 18));
    add(new SetSizeButton(300, 200));
    add(new SetSizeButton(400, 300));
    add(new SetSizeButton(500, 400));
    setSize(400, 300);
    setVisible(true);
  }
}
********************
CloseableFrame.java 
********************
import java.awt.*;
import java.awt.event.*;

/** A Frame that you can actually quit. Used as the starting 
 *  point for most Java 1.1 graphical applications.
 ***********************

public class CloseableFrame extends Frame {
  public CloseableFrame(String title) {
    super(title);
    enableEvents(AWTEvent.WINDOW_EVENT_MASK);
  }

  /** Since we are doing something permanent, we need
   *  to call super.processWindowEvent first.
   */
  
  public void processWindowEvent(WindowEvent event) {
    super.processWindowEvent(event); // Handle listeners.
    if (event.getID() == WindowEvent.WINDOW_CLOSING) {
      // If the frame is used in an applet, use dispose().
      System.exit(0);
    }
  }
}
**********************
SetSizeButton.java
**********************
import java.awt.*;
import java.awt.event.*;

///////////////////////
public class SetSizeButton extends Button 
                           implements ActionListener {
  private int width, height;

  public SetSizeButton(int width, int height) {
    super("Resize to " + width + "x" + height);
    this.width = width;
    this.height = height;
    addActionListener(this);
  }

  public void actionPerformed(ActionEvent event) {
    getParent().setSize(width, height);
    getParent().invalidate();
    getParent().validate();
  }
}
***********************
ActionExample2.java
***********************
import java.awt.*;
import java.awt.event.*;

/***********/
public class ActionExample2 extends CloseableFrame
                            implements ActionListener {
  public static void main(String[] args) {
    new ActionExample2();
  }

  private Button button1, button2, button3;

  public ActionExample2() {
    super("Handling Events in Other Object");
    setLayout(new FlowLayout());
    setFont(new Font("Serif", Font.BOLD, 18));
    button1 = new Button("Resize to 300x200");
    button2 = new Button("Resize to 400x300");
    button3 = new Button("Resize to 500x400");
    button1.addActionListener(this);
    button2.addActionListener(this);
    button3.addActionListener(this);
    add(button1);
    add(button2);
    add(button3);
    setSize(400, 300);
    setVisible(true);
  }

  public void actionPerformed(ActionEvent event) {
    if (event.getSource() == button1) {
      updateLayout(300, 200);
    } else if (event.getSource() == button2) {
      updateLayout(400, 300);
    } else if (event.getSource() == button3) {
      updateLayout(500, 400);
    }
  }
  
  private void updateLayout(int width, int height) {
    setSize(width, height);
    invalidate();
    validate();
  }
}
****************/>
CloseableFrame.java.
****************/><
import java.awt.*;
import java.awt.event.*;

/** A Frame that you can actually quit. Used as the starting 
 *  point for most Java 1.1 graphical applications.
 *
 *********************

public class CloseableFrame extends Frame {
  public CloseableFrame(String title) {
    super(title);
    enableEvents(AWTEvent.WINDOW_EVENT_MASK);
  }

  /** Since we are doing something permanent, we need
   *  to call super.processWindowEvent first.
   */
  
  public void processWindowEvent(WindowEvent event) {
    super.processWindowEvent(event); // Handle listeners.
    if (event.getID() == WindowEvent.WINDOW_CLOSING) {
      // If the frame is used in an applet, use dispose().
      System.exit(0);
    }
  }
}
***************

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

/** A Frame that uses the Confirm dialog to verify that
 *  users really want to quit.
 *
 
public class ConfirmTest extends Frame {
  public static void main(String[] args) {
    new ConfirmTest();
  }

  public ConfirmTest() {
    super("Confirming QUIT");
    setSize(200, 200);
    addWindowListener(new ConfirmListener());
    setVisible(true);
  }

  public ConfirmTest(String title) {
    super(title);
  }

  private class ConfirmListener extends WindowAdapter {
    public void windowClosing(WindowEvent event) {
      new Confirm(ConfirmTest.this);
    }
  }
}
****************
Confirm.java
****************
dialog box with two buttons: Yes and No
****************
import java.awt.*;
import java.awt.event.*;

/** A modal dialog box with two buttons: Yes and No.
 *  Clicking Yes exits Java. Clicking No exits the
 *  dialog. Used for confirmed quits from frames.
 ********************

class Confirm extends Dialog implements ActionListener {
  private Button yes, no;

  public Confirm(Frame parent) {
    super(parent, "Confirmation", true);
    setLayout(new FlowLayout());
    add(new Label("Really quit?"));
    yes = new Button("Yes");
    yes.addActionListener(this);
    no  = new Button("No");
    no.addActionListener(this);
    add(yes);
    add(no);
    pack();
    setVisible(true);
  }

  public void actionPerformed(ActionEvent event) {
    if (event.getSource() == yes) {
      System.exit(0);
    } else {
      dispose();
    }
  }
}
***************

import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;

/** Draw circles centered where the user clicks.
 *  Uses named inner classes.
 *  


 ******************

public class CircleDrawer3 extends Applet {
  public void init() {
    setForeground(Color.blue);
    addMouseListener(new CircleListener());
  }

  private class CircleListener extends MouseAdapter {
    private int radius = 25;

    public void mousePressed(MouseEvent event) {
      Graphics g = getGraphics();
      g.fillOval(event.getX()-radius,
                 event.getY()-radius,
                 2*radius,
                 2*radius);
    }
  }
}