Aug 25

Demonstrates the use of a JColorChooser which presents a dialog with three different tabbed panes to allow the user to select a color preference

Demonstrates the use of a JColorChooser which presents a dialog with three different tabbed panes to allow the user to select a color preference. The dialog returns a Color object based on the user’s selection or null if the user entered Cancel.

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

/** Simple example illustrating the use of JColorChooser. 
 *
 *  .
 */

public class JColorChooserTest extends JFrame
                               implements ActionListener {
  public static void main(String[] args) {
    new JColorChooserTest();
  }

  public JColorChooserTest() {
    super("Using JColorChooser");
    WindowUtilities.setNativeLookAndFeel();
    addWindowListener(new ExitListener());
    Container content = getContentPane();
    content.setBackground(Color.white);
    content.setLayout(new FlowLayout());
    JButton colorButton
      = new JButton("Choose Background Color");
    colorButton.addActionListener(this);
    content.add(colorButton);
    setSize(300, 100);
    setVisible(true);
  }

  public void actionPerformed(ActionEvent e) {
    // Args are parent component, title, initial color.
    Color bgColor
      = JColorChooser.showDialog(this,
                                 "Choose Background Color",
                                 getBackground());
    if (bgColor != null)
      getContentPane().setBackground(bgColor);
  }
}

Aug 25

WebClient – Client application that can talk interactively to Web servers. Requires the components listed below 

import java.awt.*; // For BorderLayout, GridLayout, Font, Color.
import java.awt.event.*;
import java.util.*;
import javax.swing.*;

/** A graphical client that lets you interactively connect to
 *  Web servers and send custom request lines and
 *  request headers.
 *
 *  Taken from Core Web Programming from
 *  Prentice Hall and Sun Microsystems Press,
 *  .
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted.
 */

public class WebClient extends JPanel
    implements Runnable, Interruptible, ActionListener {
  public static void main(String[] args) {
    WindowUtilities.setNativeLookAndFeel();
    WindowUtilities.openInJFrame(new WebClient(), 600, 700,
                                 "Web Client",
                                 SystemColor.control);
  }

  private LabeledTextField hostField, portField,
          requestLineField;
  private JTextArea requestHeadersArea, resultArea;
  private String host, requestLine;
  private int port;
  private String[] requestHeaders = new String[30];
  private JButton submitButton, interruptButton;
  private boolean isInterrupted = false;

  public WebClient() {
    setLayout(new BorderLayout(5, 30));
    int fontSize = 14;
    Font labelFont =
      new Font("Serif", Font.BOLD, fontSize);
    Font headingFont =
      new Font("SansSerif", Font.BOLD, fontSize+4);
    Font textFont =
      new Font("Monospaced", Font.BOLD, fontSize-2);
    JPanel inputPanel = new JPanel();
    inputPanel.setLayout(new BorderLayout());
    JPanel labelPanel = new JPanel();
    labelPanel.setLayout(new GridLayout(4,1));
    hostField = new LabeledTextField("Host:", labelFont,
                                     30, textFont);
    portField = new LabeledTextField("Port:", labelFont,
                                     "80", 5, textFont);
    // Use HTTP 1.0 for compatibility with the most servers.
    // If you switch this to 1.1, you *must* supply a
    // Host: request header.
    requestLineField =
      new LabeledTextField("Request Line:", labelFont,
                           "GET / HTTP/1.0", 50, textFont);
    labelPanel.add(hostField);
    labelPanel.add(portField);
    labelPanel.add(requestLineField);
    JLabel requestHeadersLabel =
      new JLabel("Request Headers:");
    requestHeadersLabel.setFont(labelFont);
    labelPanel.add(requestHeadersLabel);
    inputPanel.add(labelPanel, BorderLayout.NORTH);
    requestHeadersArea = new JTextArea(5, 80);
    requestHeadersArea.setFont(textFont);
    JScrollPane headerScrollArea =
      new JScrollPane(requestHeadersArea);
    inputPanel.add(headerScrollArea, BorderLayout.CENTER);
    JPanel buttonPanel = new JPanel();
    submitButton = new JButton("Submit Request");
    submitButton.addActionListener(this);
    submitButton.setFont(labelFont);
    buttonPanel.add(submitButton);
    inputPanel.add(buttonPanel, BorderLayout.SOUTH);
    add(inputPanel, BorderLayout.NORTH);
    JPanel resultPanel = new JPanel();
    resultPanel.setLayout(new BorderLayout());
    JLabel resultLabel =
      new JLabel("Results", JLabel.CENTER);
    resultLabel.setFont(headingFont);
    resultPanel.add(resultLabel, BorderLayout.NORTH);
    resultArea = new JTextArea();
    resultArea.setFont(textFont);
    JScrollPane resultScrollArea =
      new JScrollPane(resultArea);
    resultPanel.add(resultScrollArea, BorderLayout.CENTER);
    JPanel interruptPanel = new JPanel();
    interruptButton = new JButton("Interrupt Download");
    interruptButton.addActionListener(this);
    interruptButton.setFont(labelFont);
    interruptPanel.add(interruptButton);
    resultPanel.add(interruptPanel, BorderLayout.SOUTH);
    add(resultPanel, BorderLayout.CENTER);
  }

  public void actionPerformed(ActionEvent event) {
    if (event.getSource() == submitButton) {
      Thread downloader = new Thread(this);
      downloader.start();
    } else if (event.getSource() == interruptButton) {
      isInterrupted = true;
    }
  }

  public void run() {
    isInterrupted = false;
    if (hasLegalArgs())
      new HttpClient(host, port, requestLine,
             requestHeaders, resultArea, this);
  }

  public boolean isInterrupted() {
    return(isInterrupted);
  }

  private boolean hasLegalArgs() {
    host = hostField.getTextField().getText();
    if (host.length() == 0) {
      report("Missing hostname");
      return(false);
    }
    String portString =
      portField.getTextField().getText();
    if (portString.length() == 0) {
      report("Missing port number");
      return(false);
    }
    try {
      port = Integer.parseInt(portString);
    } catch(NumberFormatException nfe) {
      report("Illegal port number: " + portString);
      return(false);
    }
    requestLine =
      requestLineField.getTextField().getText();
    if (requestLine.length() == 0) {
      report("Missing request line");
      return(false);
    }
    getRequestHeaders();
    return(true);
  }

  private void report(String s) {
    resultArea.setText(s);
  }

  private void getRequestHeaders() {
    for(int i=0; i
   *    LabeledTextField ltf = new LabeledTextField(...);
   *    ltf.getLabel().someLabelMethod(...);
   *

*/ public JLabel getLabel() { return(label); } /** The TextField at the right side of the * LabeledTextField. */ public JTextField getTextField() { return(textField); } } Interruptible.java Polls to see if the user choose to interrupt the current network download. /** An interface for classes that can be polled to see * if they’ve been interrupted. Used by HttpClient * and WebClient to allow the user to interrupt a network * download. * * Taken from Core Web Programming from * Prentice Hall and Sun Microsystems Press, * . * © 2001 Marty Hall and Larry Brown; * may be freely used or adapted. */ public interface Interruptible { public boolean isInterrupted(); } NetworkClient.java Starting point for a network client to communicate with a remote computer. import java.net.*; import java.io.*; /** A starting point for network clients. You’ll need to * override handleConnection, but in many cases connect can * remain unchanged. It uses SocketUtil to simplify the * creation of the PrintWriter and BufferedReader. * * Taken from Core Web Programming from * Prentice Hall and Sun Microsystems Press, * © 2001 Marty Hall and Larry Brown; * may be freely used or adapted. */ public class NetworkClient { protected String host; protected int port; /** Register host and port. The connection won’t * actually be established until you call * connect. */ public NetworkClient(String host, int port) { this.host = host; this.port = port; } /** Establishes the connection, then passes the socket * to handleConnection. */ public void connect() { try { Socket client = new Socket(host, port); handleConnection(client); } catch(UnknownHostException uhe) { System.out.println(“Unknown host: ” + host); uhe.printStackTrace(); } catch(IOException ioe) { System.out.println(“IOException: ” + ioe); ioe.printStackTrace(); } } /** This is the method you will override when * making a network client for your task. * The default version sends a single line * (“Generic Network Client”) to the server, * reads one line of response, prints it, then exits. */ protected void handleConnection(Socket client) throws IOException { PrintWriter out = SocketUtil.getWriter(client); BufferedReader in = SocketUtil.getReader(client); out.println(“Generic Network Client”); System.out.println (“Generic Network Client:\n” + “Made connection to ” + host + ” and got ‘” + in.readLine() + “‘ in response”); client.close(); } /** The hostname of the server we’re contacting. */ public String getHost() { return(host); } /** The port connection will be made on. */ public int getPort() { return(port); } } SocketUtil.java: Provides utilities for wrapping a BufferedReader and PrintWriter around the Socket’s input and output streams, respectively. import java.net.*; import java.io.*; /** A shorthand way to create BufferedReaders and * PrintWriters associated with a Socket. * * Taken from Core Web Programming from * Prentice Hall and Sun Microsystems Press, * . * © 2001 Marty Hall and Larry Brown; * may be freely used or adapted. */ public class SocketUtil { /** Make a BufferedReader to get incoming data. */ public static BufferedReader getReader(Socket s) throws IOException { return(new BufferedReader( new InputStreamReader(s.getInputStream()))); } /** Make a PrintWriter to send outgoing data. * This PrintWriter will automatically flush stream * when println is called. */ public static PrintWriter getWriter(Socket s) throws IOException { // Second argument of true means autoflush. return(new PrintWriter(s.getOutputStream(), true)); } } WindowUtilities.java Simplifies the setting of native look and feel. import javax.swing.*; import java.awt.*; // For Color and Container classes. /** A few utilities that simplify using windows in Swing. * * Taken from Core Web Programming from * Prentice Hall and Sun Microsystems Press, * © 2001 Marty Hall and Larry Brown; * may be freely used or adapted. */ public class WindowUtilities { /** Tell system to use native look and feel, as in previous * releases. Metal (Java) LAF is the default otherwise. */ public static void setNativeLookAndFeel() { try { UIManager.setLookAndFeel( UIManager.getSystemLookAndFeelClassName()); } catch(Exception e) { System.out.println(“Error setting native LAF: ” + e); } } public static void setJavaLookAndFeel() { try { UIManager.setLookAndFeel( UIManager.getCrossPlatformLookAndFeelClassName()); } catch(Exception e) { System.out.println(“Error setting Java LAF: ” + e); } } public static void setMotifLookAndFeel() { try { UIManager.setLookAndFeel( “com.sun.java.swing.plaf.motif.MotifLookAndFeel”); } catch(Exception e) { System.out.println(“Error setting Motif LAF: ” + e); } } /** A simplified way to see a JPanel or other Container. Pops * up a JFrame with specified Container as the content pane. */ public static JFrame openInJFrame(Container content, int width, int height, String title, Color bgColor) { JFrame frame = new JFrame(title); frame.setBackground(bgColor); content.setBackground(bgColor); frame.setSize(width, height); frame.setContentPane(content); frame.addWindowListener(new ExitListener()); frame.setVisible(true); return(frame); } /** Uses Color.white as the background color. */ public static JFrame openInJFrame(Container content, int width, int height, String title) { return(openInJFrame(content, width, height, title, Color.white)); } /** Uses Color.white as the background color, and the * name of the Container’s class as the JFrame title. */ public static JFrame openInJFrame(Container content, int width, int height) { return(openInJFrame(content, width, height, content.getClass().getName(), Color.white)); } } ExitListener.java WindowListener for applications in this chapter. import java.awt.*; import java.awt.event.*; /** A listener that you attach to the top-level JFrame of * your application, so that quitting the frame exits the * application. * * Taken from Core Web Programming from * Prentice Hall and Sun Microsystems Press, * © 2001 Marty Hall and Larry Brown; * may be freely used or adapted. */ public class ExitListener extends WindowAdapter { public void windowClosing(WindowEvent event) { System.exit(0); } }

Aug 25

EchoServer.java A simple HTTP server that creates a Web page showing all data sent from the client (browser), including all HTTP request headers sent form the client. Uses the following classes

EchoServer.java  A simple HTTP server that creates a Web page showing all data sent from the client (browser), including all HTTP request headers sent form the client. Uses the following classes:

 

import java.net.*;
import java.io.*;
import java.util.StringTokenizer;

/** A simple HTTP server that generates a Web page showing all
 *  of the data that it received from the Web client (usually
 *  a browser). To use this server, start it on the system of
 *  your choice, supplying a port number if you want something
 *  other than port 8088. Call this system server.com. Next,
 *  start a Web browser on the same or a different system, and
 *  connect to http://server.com:8088/whatever. The resultant
 *  Web page will show the data that your browser sent. For
 *  debugging in servlet or CGI programming, specify
 *  http://server.com:8088/whatever as the ACTION of your HTML
 *  form. You can send GET or POST data; either way, the
 *  resultant page will show what your browser sent.
 *
 *  Taken from Core Web Programming from
 *  Prentice Hall and Sun Microsystems Press,
 *  .
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted.
 */

public class EchoServer extends NetworkServer {
  protected int maxRequestLines = 50;
  protected String serverName = "EchoServer";

  /** Supply a port number as a command-line
   *  argument. Otherwise, use port 8088.
   */

  public static void main(String[] args) {
    int port = 8088;
    if (args.length > 0) {
      try {
        port = Integer.parseInt(args[0]);
      } catch(NumberFormatException nfe) {}
    }
    new EchoServer(port, 0);
  }

  public EchoServer(int port, int maxConnections) {
    super(port, maxConnections);
    listen();
  }

  /** Overrides the NetworkServer handleConnection method to
   *  read each line of data received, save it into an array
   *  of strings, then send it back embedded inside a PRE
   *  element in an HTML page.
   */

  public void handleConnection(Socket server)
      throws IOException{
    System.out.println
        (serverName + ": got connection from " +
         server.getInetAddress().getHostName());
    BufferedReader in = SocketUtil.getReader(server);
    PrintWriter out = SocketUtil.getWriter(server);
    String[] inputLines = new String[maxRequestLines];
    int i;
    for (i=0; i\n" +
       "\n" +
       "\n" +
       "  \n" +
       "\n" +
       "\n" +
       "\n" +
       "
" + serverName +
         " Results
\n" +
       "Here is the request line and request headers\n" +
       "sent by your browser:\n" +
       "

");
  }

  // Print bottom of a standard Web page.

  private void printTrailer(PrintWriter out) {
    out.println
      ("

\n" +
       "\n" +
       "\n");
  }

  // Normal Web page requests use GET, so this server can simply
  // read a line at a time. However, HTML forms can also use
  // POST, in which case we have to determine the number of POST
  // bytes that are sent so we know how much extra data to read
  // after the standard HTTP headers.

  private boolean usingPost(String[] inputs) {
    return(inputs[0].toUpperCase().startsWith("POST"));
  }

  private void readPostData(String[] inputs, int i,
                            BufferedReader in)
      throws IOException {
    int contentLength = contentLength(inputs);
    char[] postData = new char[contentLength];
    in.read(postData, 0, contentLength);
    inputs[++i] = new String(postData, 0, contentLength);
  }

  // Given a line that starts with Content-Length,
  // this returns the integer value specified.

  private int contentLength(String[] inputs) {
    String input;
    for (int i=0; iOverride this method in servers
   *  you write.
   *  


   *  This generic version simply reports the host that made
   *  the connection, shows the first line the client sent,
   *  and sends a single line in response.
   */

  protected void handleConnection(Socket server)
      throws IOException{
    BufferedReader in = SocketUtil.getReader(server);
    PrintWriter out = SocketUtil.getWriter(server);
    System.out.println
      ("Generic Network Server: got connection from " +
       server.getInetAddress().getHostName() + "\n" +
       "with first line '" + in.readLine() + "'");
    out.println("Generic Network Server");
    server.close();
  }

  /** Gets the max connections server will handle before
   *  exiting. A value of 0 indicates that server should run
   *  until explicitly killed.
   */

  public int getMaxConnections() {
    return(maxConnections);
  }

  /** Sets max connections. A value of 0 indicates that server
   *  should run indefinitely (until explicitly killed).
   */

  public void setMaxConnections(int maxConnections) {
    this.maxConnections = maxConnections;
  }

  /** Gets port on which server is listening. */

  public int getPort() {
    return(port);
  }

  /** Sets port. You can only do before "connect" is
   *  called. That usually happens in the constructor.
   */

  protected void setPort(int port) {
    this.port = port;
  }
}


SocketUtil.java  Simplifies the creation of a PrintWriter and BufferedReader.

import java.net.*;
import java.io.*;

/** A shorthand way to create BufferedReaders and
 *  PrintWriters associated with a Socket.
 *
 *  Taken from Core Web Programming from 
 *  Prentice Hall and Sun Microsystems Press,
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted. 
 */

public class SocketUtil {
  /** Make a BufferedReader to get incoming data. */

  public static BufferedReader getReader(Socket s)
      throws IOException {
    return(new BufferedReader(
       new InputStreamReader(s.getInputStream())));
  }

  /** Make a PrintWriter to send outgoing data.
   *  This PrintWriter will automatically flush stream
   *  when println is called.
   */

  public static PrintWriter getWriter(Socket s)
      throws IOException {
    // Second argument of true means autoflush.
    return(new PrintWriter(s.getOutputStream(), true));
  }
}

Aug 25

StoppableThread.java A template to place a thread in a RUN, WAIT, or STOP state. 

/** A template to control the state of a thread through setting
 *  an internal flag.

public class StoppableThread extends Thread {

   public static final int STOP    = 0;
   public static final int RUN     = 1;
   public static final int WAIT    = 2;
   private int state = RUN;

  /** Public method to permit setting a flag to stop or
   *  suspend the thread.  The state is monitored through the
   *  corresponding checkState method.
   */

   public synchronized void setState(int state) {
      this.state = state;
      if (state==RUN) {
         notify();
      }
   }

  /** Returns the desired state of the thread (RUN, STOP, WAIT).
   *  Normally, you may want to change the state or perform some
   *  other task if an InterruptedException occurs.
   */

   private synchronized int checkState() {
      while (state==WAIT) {
        try {
          wait();
        } catch (InterruptedException e) { }
      }
      return state;
   }

  /** An example of thread that will continue to run until
   *  the creating object tells the thread to STOP.
   */

   public void run() {
      while (checkState()!=STOP) {
         ...
      }
   }
}

Aug 25

mall example showing the basic use of a JToolBar 

mall example showing the basic use of a JToolBar

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

/** Small example showing basic use of JToolBar. 
 *
 * 
 */

public class JToolBarExample extends JFrame
                             implements ItemListener {
  private BrowserToolBar toolbar;
  private JCheckBox labelBox;

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

  public JToolBarExample() {
    super("JToolBar Example");
    WindowUtilities.setNativeLookAndFeel();
    addWindowListener(new ExitListener());
    Container content = getContentPane();
    content.setBackground(Color.white);
    
    JPanel panel = new JPanel(new BorderLayout());
    labelBox = new JCheckBox("Show Text Labels?");
    labelBox.setHorizontalAlignment(SwingConstants.CENTER);
    labelBox.addItemListener(this);
    panel.add(new JTextArea(10,30), BorderLayout.CENTER);
    panel.add(labelBox, BorderLayout.SOUTH);

    toolbar = new BrowserToolBar();
    content.add(toolbar, BorderLayout.NORTH);
    content.add(panel, BorderLayout.CENTER);

    pack();
    setVisible(true);
  }

  public void itemStateChanged(ItemEvent event) {
    toolbar.setTextLabels(labelBox.isSelected());
    pack();
  }
}

Aug 25

UrlRetriever2.java Illustrates how the URL class can simplify communication to an HTTP server. 

UrlRetriever2.java  Illustrates how the URL class can simplify communication to an HTTP server.

import java.net.*;
import java.io.*;

/** Read a remote file using the standard URL class
 *  instead of connecting explicitly to the HTTP server.
 *
 *  Taken from Core Web Programming from
 *  Prentice Hall and Sun Microsystems Press,
 *  .
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted.
 */

public class UrlRetriever2 {
  public static void main(String[] args) {
    checkUsage(args);
    try {
      URL url = new URL(args[0]);
      BufferedReader in = new BufferedReader(
        new InputStreamReader(url.openStream()));
      String line;
      while ((line = in.readLine()) != null) {
        System.out.println("> " + line);
     }
      in.close();
    } catch(MalformedURLException mue) { // URL constructor
        System.out.println(args[0] + "is an invalid URL: " + mue);
    } catch(IOException ioe) { // Stream constructors
      System.out.println("IOException: " + ioe);
    }
  }

  private static void checkUsage(String[] args) {
    if (args.length != 1) {
      System.out.println("Usage: UrlRetriever2 ");
      System.exit(-1);
    }
  }
}

Aug 25

RMI Example – Message, illustrates retrieving a message from an object located on a remote server. Requires the following classes 

Rem.java  Establishes which methods the client can access in the remote object. 





import java.rmi.*;

/** The RMI client will use this interface directly. The RMI
 *  server will make a real remote object that implements this,
 *  then register an instance of it with some URL.
 *
 *  Taken from Core Web Programming from
 *  Prentice Hall and Sun Microsystems Press,
 *  .
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted.
 */

public interface Rem extends Remote {
  public String getMessage() throws RemoteException;
}


RemClient.java  The client application which communicates to the remote object and retrieves the message. 

import java.rmi.*; // For Naming, RemoteException, etc.
import java.net.*; // For MalformedURLException
import java.io.*;  // For Serializable interface

/** Get a Rem object from the specified remote host.
 *  Use its methods as though it were a local object.
 *
 *  Taken from Core Web Programming from
 *  Prentice Hall and Sun Microsystems Press,
 *  .
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted.
 */

public class RemClient {
  public static void main(String[] args) {
    try {
      String host =
        (args.length > 0) ? args[0] : "localhost";
      // Get the remote object and store it in remObject:
      Rem remObject =
        (Rem)Naming.lookup("rmi://" + host + "/Rem");
      // Call methods in remObject:
      System.out.println(remObject.getMessage());
    } catch(RemoteException re) {
      System.out.println("RemoteException: " + re);
    } catch(NotBoundException nbe) {
      System.out.println("NotBoundException: " + nbe);
    } catch(MalformedURLException mfe) {
      System.out.println("MalformedURLException: " + mfe);
    }
  }
}


RemImpl.java  The concrete, remote object that implements the methods in Rem.java. 

import java.rmi.*;
import java.rmi.server.UnicastRemoteObject;

/** This is the actual implementation of Rem that the RMI
 *  server uses. The server builds an instance of this, then
 *  registers it with a URL. The client accesses the URL and
 *  binds the result to a Rem (not a RemImpl; it doesn't
 *  have this).
 *
 *  Taken from Core Web Programming from
 *  Prentice Hall and Sun Microsystems Press,
 *  .
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted.
 */

public class RemImpl extends UnicastRemoteObject
                     implements Rem {
  public RemImpl() throws RemoteException {}

  public String getMessage() throws RemoteException {
    return("Here is a remote message.");
  }
}


RemServer.java  Creates an instance of RemImpl on the remote server and binds the object in the registry for lookup by the client. 

import java.rmi.*;
import java.net.*;

/** The server creates a RemImpl (which implements the Rem
 *  interface), then registers it with the URL Rem, where
 *  clients can access it.
 *
 *  Taken from Core Web Programming from
 *  Prentice Hall and Sun Microsystems Press,
 *  .
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted.
 */

public class RemServer {
  public static void main(String[] args) {
    try {
      RemImpl localObject = new RemImpl();
      Naming.rebind("rmi:///Rem", localObject);
    } catch(RemoteException re) {
      System.out.println("RemoteException: " + re);
    } catch(MalformedURLException mfe) {
      System.out.println("MalformedURLException: " + mfe);
    }
  }
}

Aug 25

Creates three common types of sliders 

Creates three common types of sliders: one without tick marks, one with tick marks, and one with both tick marks and labels. 

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

/** Simple example illustrating the use of JSliders, especially
 *  the ability to specify tick marks and labels.
 *
 *   
 */

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

  public JSliders() {
    super("Using JSlider");
    WindowUtilities.setNativeLookAndFeel();
    addWindowListener(new ExitListener());
    Container content = getContentPane();
    content.setBackground(Color.white);
    
    JSlider slider1 = new JSlider();
    slider1.setBorder(BorderFactory.createTitledBorder
                        ("JSlider without Tick Marks"));
    content.add(slider1, BorderLayout.NORTH);
    
    JSlider slider2 = new JSlider();
    slider2.setBorder(BorderFactory.createTitledBorder
                        ("JSlider with Tick Marks"));
    slider2.setMajorTickSpacing(20);
    slider2.setMinorTickSpacing(5);
    slider2.setPaintTicks(true);
    content.add(slider2, BorderLayout.CENTER);

    JSlider slider3 = new JSlider();
    slider3.setBorder(BorderFactory.createTitledBorder
                        ("JSlider with Tick Marks & Labels"));
    slider3.setMajorTickSpacing(20);
    slider3.setMinorTickSpacing(5);
    slider3.setPaintTicks(true);
    slider3.setPaintLabels(true);
    content.add(slider3, BorderLayout.SOUTH);
    
    pack();
    setVisible(true);
  }
}

Aug 25

Basic Swing Details

  • WindowUtilities.java Utility class that simplifies creating a window and setting the look and feel.
  • ExitListener.java A WindowListener with support to close the window.
  • JAppletExample.java A simple applet (JApplet) created in Swing. Illustrates setting the look and feel, adding components to the content pane, and changing the layout to FlowLayout (default is BorderLayout). See JAppletExample.html (requires the Java Plug-In or a Java 2 compliant browser, for example, Netscape 6.x).
  • JFrameExample.java Demonstrates creating a simple Swing application using a JFrame. As with a JApplet, components must be added to the content pane, instead of the window directly.
  • JLabels.java Illustrates creating labels in Swing. A nice feature of JLabels is that the label text can contain HTML markup. Uses image JHUAPL.gif
  • JButtons.java Creates various buttons. In Swing, buttons can contain text only, an image only, or a combination of both an image and a label. Uses image cup.gif.
  • JPanels.java A simple example that illustrates creating panels. In Swing, a JPanel can contain custom borders. Typically, utility methods in the BorderFactory class are used to create a border for the panel. Uses the following class:
    o SixChoicePanel.java A JPanel that displays six radio buttons with labels.
  • JSliders.java Creates three common types of sliders: one without tick marks, one with tick marks, and one with both tick marks and labels.
  • JColorChooserTest.java Demonstrates the use of a JColorChooser which presents a dialog with three different tabbed panes to allow the user to select a color preference. The dialog returns a Color object based on the user’s selection or null if the user entered Cancel.
  • JInternalFrames.java Illustrates the ability to create a Multiple Document Interface (MDI) application by placing internal frames (JInternalFrame) in a desktop pane (JDesktopPane).
  • JToolBarExample.java Small example showing the basic use of a JToolBar. Uses the following classes and images:
    o ToolBarButton.java A simple button that contains an image and a label for use in a toolbar.
    o BrowserToolBar.java A basic tool bar for holding multiple buttons.
    o Images used in the toolbar buttons: Help.gif, Home.gif, Left.gif, Print.gif, Right.gif, RotCCUp.gif, TrafficRed.gif.
  • Browser.java Implementation of a simple browser in Swing. The user can specify a URL to load into the browser (JEditorPane). By attaching an HyperlinkListener, the editor pane is responsive to hyperlinks selected by the user. Uses the following class and image:
    o JIconButton.java A simple button that the user can select to load the entered URL.
    o home.gif Image used in the button.
  • JCheckBoxTest.java Simple example illustrating the use of check boxes.
  • JRadioButtonTest.java Creates three radio buttons and illustrates handling ItemEvents in response to selecting a radio button.
  • JOptionPaneExamples.java Creates various modal dialogs to show messages. Uses the follwoing classes:
    o JLabeledTextField.java A simple JPanel that combines a JLabel and a JTextField.
    o RadioButtonPanel.java Groups several radio buttons in a single row, with a label on the left.
    o DisableListener.java A listener that toggles the enabled status of some other component.

Aug 24

UrlRetriever.java Accepts an URL from the command line, parses the host, port, and URI components from the URL and then retrieves the document. Requires the following classes 

UrlRetriever.java  Accepts an URL from the command line, parses the host, port, and URI components from the URL and then retrieves the document. Requires the following classes: 


import java.util.*;

/** This parses the input to get a host, port, and file, then
 *  passes these three values to the UriRetriever class to
 *  grab the URL from the Web.
 *
 *  Taken from Core Web Programming from
 *  Prentice Hall and Sun Microsystems Press,
 *  .
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted.
 */

public class UrlRetriever {
  public static void main(String[] args) {
    checkUsage(args);
    StringTokenizer tok = new StringTokenizer(args[0]);
    String protocol = tok.nextToken(":");
    checkProtocol(protocol);
    String host = tok.nextToken(":/");
    String uri;
    int port = 80;
    try {
      uri = tok.nextToken("");
      if (uri.charAt(0) == ':') {
        tok = new StringTokenizer(uri);
        port = Integer.parseInt(tok.nextToken(":/"));
        uri = tok.nextToken("");
      }
    } catch(NoSuchElementException nsee) {
      uri = "/";
    }
    UriRetriever uriClient = new UriRetriever(host, port, uri);
    uriClient.connect();
  }

  /** Warn user if the URL was forgotten. */

  private static void checkUsage(String[] args) {
    if (args.length != 1) {
      System.out.println("Usage: UrlRetriever ");
      System.exit(-1);
    }
  }

  /** Tell user that this can only handle HTTP. */

  private static void checkProtocol(String protocol) {
    if (!protocol.equals("http")) {
      System.out.println("Don't understand protocol " + protocol);
      System.exit(-1);
    }
  }
}




UriRetriever.java  Given a host, port, and URI, retrieves the document from the HTTP server. 

import java.net.*;
import java.io.*;

/** Retrieve a URL given the host, port, and file as three 
 *  separate command-line arguments. A later class 
 *  (UrlRetriever) supports a single URL instead.
 *
 *  Taken from Core Web Programming from 
 *  Prentice Hall and Sun Microsystems Press,
 
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted. 
 */

public class UriRetriever extends NetworkClient {
  private String uri;

  public static void main(String[] args) {
    UriRetriever uriClient
      = new UriRetriever(args[0], Integer.parseInt(args[1]),
                         args[2]);
    uriClient.connect();
  }

  public UriRetriever(String host, int port, String uri) {
    super(host, port); 
    this.uri = uri;
  }

  /** Send one GET line, then read the results one line at a
   *  time, printing each to standard output.
   */

  // It is safe to use blocking IO (readLine), since
  // HTTP servers close connection when done, resulting
  // in a null value for readLine.
  
  protected void handleConnection(Socket uriSocket)
      throws IOException {
    PrintWriter out = SocketUtil.getWriter(uriSocket);
    BufferedReader in = SocketUtil.getReader(uriSocket);
    out.println("GET " + uri + " HTTP/1.0\r\n");
    String line;
    while ((line = in.readLine()) != null) {
      System.out.println("> " + line);
    }
  }
}





NetworkClient.java

import java.net.*;
import java.io.*;

/** A starting point for network clients. You'll need to
 *  override handleConnection, but in many cases connect can
 *  remain unchanged. It uses SocketUtil to simplify the
 *  creation of the PrintWriter and BufferedReader.
 *
 *  Taken from Core Web Programming from
 *  Prentice Hall and Sun Microsystems Press,
 *  .
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted.
 */

public class NetworkClient {
  protected String host;
  protected int port;

  /** Register host and port. The connection won't
   *  actually be established until you call
   *  connect.
   */

  public NetworkClient(String host, int port) {
    this.host = host;
    this.port = port;
  }

  /** Establishes the connection, then passes the socket
   *  to handleConnection.
   */

  public void connect() {
    try {
      Socket client = new Socket(host, port);
      handleConnection(client);
    } catch(UnknownHostException uhe) {
      System.out.println("Unknown host: " + host);
      uhe.printStackTrace();
    } catch(IOException ioe) {
      System.out.println("IOException: " + ioe);
      ioe.printStackTrace();
    }
  }

  /** This is the method you will override when
   *  making a network client for your task.
   *  The default version sends a single line
   *  ("Generic Network Client") to the server,
   *  reads one line of response, prints it, then exits.
   */

  protected void handleConnection(Socket client)
    throws IOException {
    PrintWriter out = SocketUtil.getWriter(client);
    BufferedReader in = SocketUtil.getReader(client);
    out.println("Generic Network Client");
    System.out.println
      ("Generic Network Client:\n" +
       "Made connection to " + host +
       " and got '" + in.readLine() + "' in response");
    client.close();
  }

  /** The hostname of the server we're contacting. */

  public String getHost() {
    return(host);
  }

  /** The port connection will be made on. */

  public int getPort() {
    return(port);
  }
}

SocketUtil.java  Provides utilities for wrapping a BufferedReader  and PrintWriter around the Socket's input and output streams, respectively. 

import java.net.*;
import java.io.*;

/** A shorthand way to create BufferedReaders and
 *  PrintWriters associated with a Socket.
 *
 *  Taken from Core Web Programming from
 *  Prentice Hall and Sun Microsystems Press,
 *  .
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted.
 */

public class SocketUtil {
  /** Make a BufferedReader to get incoming data. */

  public static BufferedReader getReader(Socket s)
      throws IOException {
    return(new BufferedReader(
       new InputStreamReader(s.getInputStream())));
  }

  /** Make a PrintWriter to send outgoing data.
   *  This PrintWriter will automatically flush stream
   *  when println is called.
   */

  public static PrintWriter getWriter(Socket s)
      throws IOException {
    // Second argument of true means autoflush.
    return(new PrintWriter(s.getOutputStream(), true));
  }
}