Java 1.2 How-To/JavaHowTo.iso/code/ch10.txt

Text File | 1998-12-14 | 23KB | 1,027 lines

WriteStream.java:

import java.io.*;

public class WriteStream
{
    // This program runs as an application
    public static void main(String[] arguments)
    {
        //Create an array of data to print
        int[] allBytes = {2,4,6,8,10,12,14,16,18,20,22,24,26,28,30};
try
        {
            //declare a stream
            FileOutputStream ofile = new σFileOutputStream("bytes.dat");
for (int i=0; i < allBytes.length; i++)
                //write to the stream
                ofile.write(allBytes[i]);
            ofile.close();
        } catch (IOException e)// handle any errors
            {
                System.out.println("Error - " + e.toString());
            }//catch
    }//main
}//WriteStream






ReadStream.java:

import java.io.*;

public class ReadStream
{
    // This program runs as an application
    public static void main(String[] arguments)
    {
        try
        {
            //declare a stream
            FileInputStream ifile = new FileInputStream("bytes.dat");
boolean eof = false;
            int cntBytes = 0;
            while (!eof)
            {
               int thisVal = ifile.read();
               System.out.print( thisVal + " ");
               if (thisVal == -1)
                  eof = true;
               else
                  cntBytes++;
            } //while
            ifile.close();
            System.out.print("\nBytes read: " + cntBytes);

       } catch (IOException e)// handle any errors
            {
                System.out.println("Error - " + e.toString());
            }//catch
    }//main
}//ReadStream






BufferedWriteStream.java:

import java.io.*;

public class BufferedWriteStream
{
    // This program runs as an application
    public static void main(String[] arguments)
    {
        //Create an array of data to print
        int[] allBytes = {1,3,5,7,9,11,13,15,17,19,21,23,25,27,29};
try
        {
            //declare a stream
            FileOutputStream ofile = new FileOutputStream("bufBytes.dat");
BufferedOutputStream bufStream = new BufferedOutputStream(ofile);
for (int i=0; i < allBytes.length; i++)
                //write to the stream
                bufStream.write(allBytes[i]);
            bufStream.close();
        } catch (IOException e)// handle any errors
            {
                System.out.println("Error - " + e.toString());
            }//catch
    }//main
}//BufferedWriteStream






BufferedReadStream.java:

import java.io.*;

public class BufferedReadStream
{
    // This program runs as an application
    public static void main(String[] arguments)
    {
        try
        {
            //declare a stream
            FileInputStream ifile = new FileInputStream("bufBytes.dat");
BufferedInputStream bufStream = new BufferedInputStream(ifile);
boolean eof = false;
            int cntBytes = 0;
            while (!eof)
            {
               int thisVal = bufStream.read();
               System.out.print( thisVal + " ");
               if (thisVal == -1)
                  eof = true;
               else
                  cntBytes++;
            } //while
            bufStream.close();
            System.out.print("\nBytes read: " + cntBytes);

       } catch (IOException e)// handle any errors
            {
                System.out.println("Error - " + e.toString());
            }//catch
    }//main
}//BufferedReadStream









BufferedWriteDataStream.java:

import java.io.*;

public class BufferedWriteDataStream
{
    // This program runs as an application
    public static void main(String[] arguments)
    {
        //Create an array of data to print
        double[] allDoubles = {1.1,3.1,5.1,7.1,9.1,11.1,13.1,15.1,17.1,19.1,21.1,23.1,25.1,27.1,29.1};
try
        {
            //declare a stream and attach it to a file
            FileOutputStream ofile = new FileOutputStream("bufDouble.dat");

            //declare a buffer and attach it to a stream
            BufferedOutputStream bufStream = new BufferedOutputStream(ofile);

            //declare a data stream and assign it to a buffer
            DataOutputStream datStream = new DataOutputStream(bufStream);

            for (int i=0; i < allDoubles.length; i++)
                //write to the datastream
                datStream.writeDouble(allDoubles[i]);
            datStream.close();
        } catch (IOException e)// handle any errors
            {
                System.out.println("Error - " + e.toString());
            }//catch
    }//main
}//BufferedWriteDataStream








BufferedReadDataStream.java:

import java.io.*;

public class BufferedReadDataStream
{
    // This program runs as an application
    public static void main(String[] arguments)
    {
        try
        {
            //declare a stream
            FileInputStream ifile = new FileInputStream("bufDouble.dat");
BufferedInputStream bufStream = new BufferedInputStream(ifile);
DataInputStream datStream = new DataInputStream(bufStream);
int cntDoubles = 0;
            try
            {
                while (true)
                {
                    double thisVal = datStream.readDouble();
                    System.out.print( thisVal + " ");
                    cntDoubles++;
                } //while
            } catch (EOFException eof)
                {
                    datStream.close();
                    System.out.print("\nDoubles read: " + [ccc]
cntDoubles);
} //catch

       } catch (IOException e)// handle any errors
            {
                System.out.println("Error - " + e.toString());
            }//catch
    }//main
}//BufferedReadDataStream







BufferedWriteCharStream.java:

import java.io.*;

public class BufferedWriteCharStream
{
    // This program runs as an application
    public static void main(String[] arguments)
    {
        //Create an array of data to print
        char[] allChars = {'H','e','l','l','o',' ','W','o','r','l','d','\n'};
try
        {
            //declare a stream and attach it to a file
            FileWriter ofile = new FileWriter("bufChar.dat");

            //declare a BufferedWriter - attach it to a stream
            BufferedWriter bufStream = new BufferedWriter(ofile);

            for (int i=0; i < allChars.length; i++)
                //write to the char stream
                bufStream.write(allChars[i]);
            bufStream.close();
        } catch (IOException e)// handle any errors
            {
                System.out.println("Error - " + e.toString());
            }//catch
    }//main
}//BufferedWriteCharStream






BufferedReadCharStream.java:

import java.io.*;

public class BufferedReadCharStream
{
    // This program runs as an application
    public static void main(String[] arguments)
    {
        try
        {
            //declare a stream
            FileReader ifile = new FileReader("bufChar.dat");
            BufferedReader bufStream = new BufferedReader(ifile);
boolean eof = false;
            while (!eof)
            {
                String line = bufStream.readLine();
                if (line == null)
                    eof = true;
                else
                    System.out.println(line);
            }//while
            bufStream.close();

       } catch (IOException e)// handle any errors
            {
                System.out.println("Error - " + e.toString());
            }//catch
    }//main
}//BufferedReadStream








GetInetFile.java:

import java.awt.*;
import java.awt.event.*;
import java.net.*;
import java.io.*;

public class GetInetFile extends Frame implements Runnable
{
    Thread thread1;
    URL doc;
    TextArea body = new TextArea("Getting text...");

    public GetInetFile()
    {
       super("Get URL");
       add(body);
       try
       {
            doc = new URL("http://www.lads.com/ads/launch.html");
}//try
       catch (MalformedURLException e)
       {
            System.out.println("Bad URL:  " + doc);
       }//catch

    }//GetInetFile


    public static void main(String[] arguments)
    {
       GetInetFile frame1 = new GetInetFile();

       WindowListener l = new WindowAdapter()
       {
            public void windowClosing(WindowEvent e)
            {
                System.exit(0);
            }//windowClosing
       };//WindowListener

       frame1.addWindowListener(l);
       frame1.pack();
       frame1.setVisible(true);
       if (frame1.thread1 == null)
       {
          frame1.thread1 = new Thread(frame1);
          frame1.thread1.start();
       }//null
    }//main

    public void run()
    {
       URLConnection URLConn = null;
       InputStreamReader inStream;
       BufferedReader info;
       String line1;
       StringBuffer strBuffer = new StringBuffer();
       try
       {
          URLConn = this.doc.openConnection();
          URLConn.connect();
          body.setText("Connection opened ... ");
          inStream = new InputStreamReader(URLConn.getInputStream());
info = new BufferedReader(inStream);
          body.setText("Reading data ...");
          while ((line1 = info.readLine()) != null)
          {
                strBuffer.append(line1 + "\n");
          }//while
          body.setText(strBuffer.toString());
       }//try
       catch (IOException e)
       {
          System.out.println("IO Error:" + e.getMessage());
       }//catch
    }//run
}// class Getfile





Advertiser.java:

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

/*
 * A class which performs the banner animation
 */
class Banner extends Panel implements Runnable{

/*
 * an instance of the applet for
 * invoking methods from Advertiser class
*/
Advertiser advertiser;

/*
 * instance of thread used for animation
 */
Thread thread;

/*
 * the next banner image to be displayed
 */
Image theImage;

/*
 * width and height of the new banner image
 */
int img_width, img_height;

/*
 * offscreen image for double-buffering
 */
Image offscreen;

/*
 * offg1 is the graphics object associated with
 * offscreen image. offg2 is the clipped version
 * of offg1
 */
Graphics offg1, offg2;

/*
 * xstart, ystart - x and y coordinate of clipping rectangle
 * width, height - width and height of clipping rectangle
 * effect_type - the effect type applied the next image
 */
int xstart, ystart, width, height, effect_type;

/**
 * constructor just saves instance of the applet
 * @param advertiser - instance of Advertiser applet
 */
Banner (Advertiser advertiser) {

    this.advertiser = advertiser;

}

/*
 * thread that calls repaint() every 25 ms
 * to effect animation
 */
public void run() {

    Dimension d = getSize();
    offscreen = createImage (d.width, d.height);
    offg1 = offscreen.getGraphics ();
    offg1.setFont (getFont ());
    offg1.setColor (Color.gray);
    offg1.fillRect (0, 0, d.width, d.height);
    while (true) {
        repaint ();
        try {
            Thread.sleep (25);
        } catch (InterruptedException e) {
            break;
        }
    }
}

/**
 * override update() method to avoid erase flicker
 * this is where the drawing is done
 * @param g - destination graphics object
 */
public synchronized void update(Graphics g) {

    int i, x, y, w, h;
    switch (effect_type) {
        case 0:
        offg1.drawImage (theImage, 0, 0, null);
        break;

        case 1:        // barn-door open
        if (xstart > 0) {
            xstart -= 5;
            width += 10;
            offg2 = offg1.create (xstart, 0, width, height);
            offg2.drawImage (theImage, -xstart, 0, null);
        } else offg1.drawImage (theImage, 0, 0, null);
        break;

        case 2:        // venetian blind
        if (height < 10) {
            height += 1;
            for (y=0; y<img_height; y+=10) {
                offg2 = offg1.create (0, y, width, height);
                offg2.drawImage (theImage, 0, -y, null);
            }
        } else offg1.drawImage (theImage, 0, 0, null);
        break;

        case 3:        // checker board
        if (width <= 20) {
            if (width <= 10) {
                i = 0;
                for (y=0; y<img_height; y+=10) {
                    for (x=(i&1)*10; x<img_width; x+=20) {
                        offg2 = offg1.create (x, y, width, 10);
                        offg2.drawImage (theImage, -x, -y, null);
}
                    i += 1;
                }
            } else {
                i = 1;
                for (y=0; y<img_height; y+=10) {
                    for (x=(i&1)*10; x<img_width; x+=20) {
                        offg2 = offg1.create (x, y, width-10, 10);
offg2.drawImage (theImage, -x, -y, null);
}
                    i += 1;
                }
            }
            width += 5;
        } else offg1.drawImage (theImage, 0, 0, null);
        break;
    }
    g.drawImage (offscreen, 0, 0, null);
}

/**
 * Initialize variables for clipping rectangle
 * depending on effect type
 * @param which - the effect type for next image
 * @param img - the next image
 */
public void effect (int which, Image img) {

    img_width = img.getWidth (null);
    img_height = img.getHeight (null);
    theImage = img;
    switch (which) {
        case 0:
        break;

        case 1:        // barn door
        xstart = img_width >> 1;
        width = 0;
        height = img_height;
        break;

        case 2:
        width = img_width;
        height = 0;
        break;

        case 3:
        width = 0;
        break;
    }
    effect_type = which;
}

/*
 * Start the repaint thread
 */
public void start() {

    thread = new Thread(this);
    thread.start();
}

/*
 * Stop the repaint thread
 */
public void stop() {

    if (thread != null)
       thread = null;
}


}

/*
 * the Advertiser class proper
*/
public class Advertiser extends Applet implements Runnable, MouseListener  {

/*
 * instance of Banner
 */
Banner panel;

/*
 * instance of thread for cycling effects
 * for each new image
 */
Thread thread;

/*
 * the total number of images
 */
int NBanners;

/*
 * the array of images
 */
Image img[] = new Image[10];

/*
 * the delay (dwell) time in milliseconds for each image
 */
int delay[] = new int[10];

/*
 * the effect type for each image
 */
int effect[] = new int[10];

/*
 * the URL to go to for each image
 */
URL url[] = new URL[10];

/*
 * the index variable pointing to the
 * current image, delay time, and associated URL
 */
int current = 0;

/*
 * called when applet is loaded
 * add the banner panel, load images, and parse applet
 * parameters
 */
public void init() {

    int i;
    setLayout(new BorderLayout());

    panel = new Banner (this);
    panel.addMouseListener(this);

    add("Center", panel);
    NBanners = 0;
    MediaTracker tracker = new MediaTracker (this);

    for (i=1; i<=10; i+=1) {
        String param, token;
        int j, next;

        param = getParameter ("T"+i);
        if (param == null) break;

        StringTokenizer st = new StringTokenizer (param, " ,");

        token = st.nextToken ();
        img[NBanners] = getImage (getDocumentBase(), token);
        tracker.addImage (img[NBanners], i);
        showStatus ("Getting image: "+token);
        try {
            tracker.waitForID (i);
        } catch (InterruptedException e) { }

        token = st.nextToken ();
        delay[NBanners] = Integer.parseInt (token);

        token = st.nextToken ();
        effect[NBanners] = Integer.parseInt (token);

        token = st.nextToken ();
        try {
            url[NBanners] = new URL (token);
        } catch (MalformedURLException e) {
            url[NBanners] = null;
        }

        NBanners += 1;
    }
}

/*
 * thread that starts the next image transition
 */
public void run () {

    while (true) {
        panel.effect (effect[current], img[current]);
        try {
            Thread.sleep (delay[current]);
        } catch (InterruptedException e) { }
        current += 1;
        current %= NBanners;
    }
}

/*
 * called when applet is started
 * start both threads
 */
public void start() {

    panel.start();
    thread = new Thread(this);
    thread.start();
}

/*
 * called when applet is stopped
 * stops all threads
 */
public void stop() {

    panel.stop();
    if (thread != null)
       thread = null;
}
/**
 * Called when user clicks in the applet
 * Force the browser to show the associated URL
 * MouseListener required methods*/
/////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////
public void mouseClicked(MouseEvent e){}
public void mouseEntered(MouseEvent e){}
public void mouseExited(MouseEvent e){}

public void mouseReleased(MouseEvent e){}


public void mousePressed(MouseEvent e)
{

    if (url[current] != null)
    {
        System.out.println("current " + url[current]);
        getAppletContext().showDocument (url[current]);
    }
}

/////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////

}







Lookup.java:

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

/*
 * Lookup application class
 */
public class Lookup extends Applet implements ActionListener  {

/*
 * text field for host name
 */
TextField nameField;

Button btnLookup;

/*
 * text area for displaying Internet addresses
 */
TextArea addrArea;

/*
 * instance of InetAddress needed for name-to-address
 * translation
 */
InetAddress inetAddr;

/*
 * insertion point in the Internet address
 * text area
 */
int insertIndex;

/*
 * constructor creates user interface
 */
public void init () {

    super.init();

    setLayout (new BorderLayout ());

    Panel editPanel = new Panel ();
    editPanel.setLayout (new BorderLayout ());
    editPanel.add ("North", new Label ("Host name"));
    nameField = new TextField ("", 32);
    btnLookup = new Button("Lookup");
    editPanel.add ("Center", nameField);
    editPanel.add ("South", btnLookup);

    add ("North", editPanel);

    Panel areaPanel = new Panel ();
    areaPanel.setLayout (new BorderLayout ());
    addrArea = new TextArea ("", 24, 32);
    addrArea.setEditable (false);
    areaPanel.add ("North", new Label ("Internet address"));
    areaPanel.add ("Center", addrArea);

    add ("Center", areaPanel);
    btnLookup.addActionListener(this);

    insertIndex = 0;

    setSize (300, 200);
}

    public void actionPerformed(ActionEvent ev)
    {
        String name = nameField.getText ();
        try
        {
            inetAddr = InetAddress.getByName (name);
            String str = inetAddr.toString () + "\n";
            addrArea.insert (str, insertIndex);
            insertIndex += str.length ();
        } catch (UnknownHostException ex)
             {
                String str = name + "/ No such host\n";
                addrArea.insert (str, insertIndex);
                insertIndex += str.length ();
             }
    }

} // end of Applet







Ping.java:

import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;

/*
 * application class
 */
public class Ping extends Frame implements Runnable, ActionListener {

/*
 * instance of Socket used for determining
 * whether remote host is alive
*/
Socket socket;

/*
 * hostname text entry field
 */
TextField addrField;

/*
 * the stop button
 */
Button stopButton;
Button startButton;

/*
 * the text area for printing remote
 * host status
 */
TextArea content;

/*
 * thread used to decouple user activity
 * from socket activity
 */
Thread thread;

/*
 * text area insert position
 */
int insertPos;

/*
 * constructor creates user interface
 */
public Ping () {

    int i;

    setTitle ("Ping");
    setLayout(new BorderLayout());

    addrField = new TextField ("", 20);
    startButton = new Button ("Start");
    stopButton = new Button ("Stop");
    content = new TextArea ("", 24, 80);
    content.setEditable (false);
    insertPos = 0;

    Panel p = new Panel ();
    p.setLayout (new FlowLayout ());
    p.add (addrField);
    p.add (startButton);
    p.add (stopButton);

    startButton.addActionListener(this);
    stopButton.addActionListener(this);
    addWindowListener(new WindowCloser());


    add ("North", p);
    add ("Center", content);

    thread = new Thread (this);

    setSize (400, 300);
    show ();
}

/**
 * handle action events
 * Enter keypress starts socket open thread
 * Stop button click stops socket thread
* @param evt - event object
 * @param obj - object receiving this event
 */
public void actionPerformed (ActionEvent ev)
{
    Object object1 = ev.getSource();
    if (object1 == startButton)
    {
        if (thread != null)
            thread = null;
        thread = new Thread (this);
        thread.start ();
    }
    if (object1 == stopButton)
    {
        if (thread!= null)
           thread = null;
    }
}

/*
 * socket open thread
 * tries to open the telnet port (23)
 */
public void run () {

    String name;

    name = addrField.getText ();
        try {
                try {
                        socket = new Socket (name, 23);
                } catch (UnknownHostException e) {
                        insertString (name+" :unknown host\n");
                        return;
                }
        } catch (IOException e2) {
                insertString ("Unable to open socket\n");
                return;
        }

    insertString (name + " is alive\n");
    try {
        socket.close ();
        } catch (IOException e2) {
                insertString ("IOException closing socket\n");

                return;
        }
}

/**
 * helper method for adding text to the end
 * of the text area
 * @param s - text to add
 */
void insertString (String s) {

    content.insert (s, insertPos);
    insertPos += s.length ();
}

/**
 * application entry point
 * @param args - command-line arguments
 */
public static void main (String args[]) {

    new Ping ();
}
}

class WindowCloser extends WindowAdapter
{
    public void windowClosing(WindowEvent e)
    {
        Window win = e.getWindow();
        win.setVisible(false);
        win.dispose();
        System.exit(0);
    }
}