//: Sharing1.java
//////////////////////////////////////////////////
// Copyright (c) Bruce Eckel, 1998
// Source code file from the book "Thinking in Java"
// All rights reserved EXCEPT as allowed by the
// following statements: You can freely use this file
// for your own work (personal or commercial),
// including modifications and distribution in
// executable form only. Permission is granted to use
// this file in classroom situations, including its
// use in presentation materials, as long as the book
// "Thinking in Java" is cited as the source.
// Except in classroom situations, you cannot copy
// and distribute this code; instead, the sole
// distribution point is http://www.BruceEckel.com
// (and official mirror sites) where it is
// freely available. You cannot remove this
// copyright and notice. You cannot distribute
// modified versions of the source code in this
// package. You cannot use this file in printed
// media without the express permission of the
// author. Bruce Eckel makes no representation about
// the suitability of this software for any purpose.
// It is provided "as is" without express or implied
// warranty of any kind, including any implied
// warranty of merchantability, fitness for a
// particular purpose or non-infringement. The entire
// risk as to the quality and performance of the
// software is with you. Bruce Eckel and the
// publisher shall not be liable for any damages
// suffered by you or any third party as a result of
// using or distributing software. In no event will
// Bruce Eckel or the publisher be liable for any
// lost revenue, profit, or data, or for direct,
// indirect, special, consequential, incidental, or
// punitive damages, however caused and regardless of
// the theory of liability, arising out of the use of
// or inability to use software, even if Bruce Eckel
// and the publisher have been advised of the
// possibility of such damages. Should the software
// prove defective, you assume the cost of all
// necessary servicing, repair, or correction. If you
// think you've found an error, please email all
// modified files with clearly commented changes to:
// Bruce@EckelObjects.com. (Please use the same
// address for non-code errors found in the book.)
/////////////////////////////////////////////////
// Problems with resource sharing while threading
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
class TwoCounter extends Thread {
private boolean started = false;
private TextField
t1 = new TextField(5),
t2 = new TextField(5);
private Label l =
new Label("count1 == count2");
private int count1 = 0, count2 = 0;
// Add the display components as a panel
// to the given container:
public TwoCounter(Container c) {
Panel p = new Panel();
p.add(t1);
p.add(t2);
p.add(l);
c.add(p);
}
public void start() {
if(!started) {
started = true;
super.start();
}
}
public void run() {
while (true) {
t1.setText(Integer.toString(count1++));
t2.setText(Integer.toString(count2++));
try {
sleep(500);
} catch (InterruptedException e){}
}
}
public void synchTest() {
Sharing1.incrementAccess();
if(count1 != count2)
l.setText("Unsynched");
}
}
class Watcher extends Thread {
private Sharing1 p;
public Watcher(Sharing1 p) {
this.p = p;
start();
}
public void run() {
while(true) {
for(int i = 0; i < p.s.length; i++)
p.s[i].synchTest();
try {
sleep(500);
} catch (InterruptedException e){}
}
}
}
public class Sharing1 extends Applet {
TwoCounter[] s;
private static int accessCount = 0;
private static TextField aCount =
new TextField("0", 10);
public static void incrementAccess() {
accessCount++;
aCount.setText(Integer.toString(accessCount));
}
private Button
start = new Button("Start"),
observer = new Button("Observe");
private boolean isApplet = true;
private int numCounters = 0;
private int numObservers = 0;
public void init() {
if(isApplet) {
numCounters =
Integer.parseInt(getParameter("size"));
numObservers =
Integer.parseInt(
getParameter("observers"));
}
s = new TwoCounter[numCounters];
for(int i = 0; i < s.length; i++)
s[i] = new TwoCounter(this);
Panel p = new Panel();
start.addActionListener(new StartL());
p.add(start);
observer.addActionListener(new ObserverL());
p.add(observer);
p.add(new Label("Access Count"));
p.add(aCount);
add(p);
}
class StartL implements ActionListener {
public void actionPerformed(ActionEvent e) {
for(int i = 0; i < s.length; i++)
s[i].start();
}
}
class ObserverL implements ActionListener {
public void actionPerformed(ActionEvent e) {
for(int i = 0; i < numObservers; i++)
new Watcher(Sharing1.this);
}
}
public static void main(String[] args) {
Sharing1 applet = new Sharing1();
// This isn't an applet, so set the flag and
// produce the parameter values from args:
applet.isApplet = false;
applet.numCounters =
(args.length == 0 ? 5 :
Integer.parseInt(args[0]));
applet.numObservers =
(args.length < 2 ? 5 :
Integer.parseInt(args[1]));
Frame aFrame = new Frame("Sharing1");
aFrame.addWindowListener(
new WindowAdapter() {
public void windowClosing(WindowEvent e){
System.exit(0);
}
});
aFrame.add(applet, BorderLayout.CENTER);
aFrame.setSize(350, applet.numCounters *100);
applet.init();
applet.start();
aFrame.setVisible(true);
}
} ///:~ |