//: c14:Sharing2.java
// Using the synchronized keyword to prevent
// multiple access to a particular resource.
// <applet code=Sharing2 width=350 height=500>
// <param name=size value="12">
// <param name=watchers value="15">
// </applet>
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() { super.start(); }
public void run() {
while(true) {
for(int i = 0; i < 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 < s.length; i++)
s[i].start();
}
}
class WatcherL implements ActionListener {
public void actionPerformed(ActionEvent e) {
for(int i = 0; i < 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 < 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 < 2 ? 15 :
Integer.parseInt(args[1]));
Console.run(applet, 350,
applet.numCounters * 50);
}
} ///:~