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<html><head><title>Display page for Sharing2 at www.BruceEckel.com</title></head><FONT FACE="Verdana,Tahoma,Arial,Helvetica,Sans"><H2>Sharing2.java</H2><hr></FONT>
<OBJECT classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
    width="350" height="500" align="baseline"
    codebase="http://java.sun.com/products/plugin/1.2.2/jinstall-1_2_2-win.cab#Version=1,2,2,0">
<PARAM NAME="code" VALUE="Sharing2.class">
<PARAM NAME="codebase" VALUE=".">
<PARAM NAME="type" VALUE="application/x-java-applet;version=1.2.2">
<COMMENT>
    <EMBED type="application/x-java-applet;version=1.2.2" 
       width="350" height="500" align="baseline" 
       code="Sharing2.class" 
       codebase="."
       pluginspage="http://java.sun.com/products/plugin/1.2/plugin-install.html">
    <NOEMBED>
    </COMMENT>
       No Java 2 support for APPLET!!
    </NOEMBED></EMBED>
</OBJECT>
<FONT SIZE="+3"><PRE><B>
//: c14:Sharing2.java
// From 'Thinking in Java, 2nd ed.' by Bruce Eckel
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
// Using the synchronized keyword to prevent
// multiple access to a particular resource.
// &lt;applet code=Sharing2 width=350 height=500&gt;
// &lt;param name=size value="12"&gt;
// &lt;param name=watchers value="15"&gt;
// &lt;/applet&gt;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import com.bruceeckel.swing.*;

public class Sharing2 extends JApplet {
  TwoCounter[] s;
  private static int accessCount = 0;
  private static JTextField aCount = 
    new JTextField("0", 7);
  public static void incrementAccess() {
    accessCount++;
    aCount.setText(Integer.toString(accessCount));
  }
  private JButton 
    start = new JButton("Start"),
    watcher = new JButton("Watch");
  private boolean isApplet = true;
  private int numCounters = 12;
  private int numWatchers = 15;

  class TwoCounter extends Thread {
    private boolean started = false;
    private JTextField 
      t1 = new JTextField(5),
      t2 = new JTextField(5);
    private JLabel l = 
      new JLabel("count1 == count2");
    private int count1 = 0, count2 = 0;
    public TwoCounter() {
      JPanel p = new JPanel();
      p.add(t1);
      p.add(t2);
      p.add(l);
      getContentPane().add(p);
    }    
    public void start() {
      if(!started) {
        started = true;
        super.start();
      }
    }
    public synchronized void run() {
      while (true) {
        t1.setText(Integer.toString(count1++));
        t2.setText(Integer.toString(count2++));
        try {
          sleep(500);
        } catch(InterruptedException e) {
          System.err.println("Interrupted");
        }
      }
    }
    public synchronized void synchTest() {
      incrementAccess();
      if(count1 != count2)
        l.setText("Unsynched");
    }
  }
  
  class Watcher extends Thread {
    public Watcher() { start(); }
    public void run() {
      while(true) {
        for(int i = 0; i &lt; s.length; i++)
          s[i].synchTest();
        try {
          sleep(500);
        } catch(InterruptedException e) {
          System.err.println("Interrupted");
        }
      }
    }
  }
  class StartL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      for(int i = 0; i &lt; s.length; i++)
        s[i].start();
    }
  }
  class WatcherL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      for(int i = 0; i &lt; numWatchers; i++)
        new Watcher();
    }
  }
  public void init() {
    if(isApplet) {
      String counters = getParameter("size");
      if(counters != null)
        numCounters = Integer.parseInt(counters);
      String watchers = getParameter("watchers");
      if(watchers != null)
        numWatchers = Integer.parseInt(watchers);
    }
    s = new TwoCounter[numCounters];
    Container cp = getContentPane();
    cp.setLayout(new FlowLayout());
    for(int i = 0; i &lt; s.length; i++)
      s[i] = new TwoCounter();
    JPanel p = new JPanel();
    start.addActionListener(new StartL());
    p.add(start);
    watcher.addActionListener(new WatcherL());
    p.add(watcher);
    p.add(new Label("Access Count"));
    p.add(aCount);
    cp.add(p);
  }
  public static void main(String[] args) {
    Sharing2 applet = new Sharing2();
    // This isn't an applet, so set the flag and
    // produce the parameter values from args:
    applet.isApplet = false;
    applet.numCounters = 
      (args.length == 0 ? 12 :
        Integer.parseInt(args[0]));
    applet.numWatchers =
      (args.length &lt; 2 ? 15 :
        Integer.parseInt(args[1]));
    Console.run(applet, 350, 
      applet.numCounters * 50);
  }
} ///:~
</B></PRE></FONT></body></html>
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