This section provides a tutorial example on how to list AWT threads and how to interrupt AWT threads with the interrupt() method.
Problem: I want to know how many threads are created by the Swing package and the AWT package,
what will happen if I send the interrupt signal to all of them.
Solution: This is easy. Just get the list of all threads of the current
thread group, and interrupt them one by one. Here is a sample program to show
you how to do this:
/**
* FrameThreads.java
* Copyright (c) 2002 by Dr. Herong Yang, http://www.herongyang.com/
*/
import java.awt.*;
import javax.swing.*;
public class FrameThreads {
public static void main(String[] a) {
JFrame f = new JFrame("Frame 1");
f.setBounds(0,0,100,100);
f.setVisible(true);
f = new JFrame("Frame 2");
f.setBounds(50,50,100,100);
f.setVisible(true);
f = new JFrame("Frame 3");
f.setBounds(100,100,100,100);
f.setVisible(true);
Thread[] l = new Thread[100];
int n = Thread.enumerate(l);
Thread g = null;
for (int i=0; i<n; i++) {
System.out.println("Active thread = "+l[i].getName());
}
Thread t = Thread.currentThread();
for (int i=0; i<n; i++) {
try {
Thread.sleep(1000*30);
} catch (Exception e) {
System.out.println("Interrupted.");
}
if (t != l[i]) {
System.out.println("Interrupting thread = "
+l[i].getName());
l[i].interrupt();
}
}
}
}
If you run this program, you will see 3 frame windows showing up on the screen.
After every 30 seconds, my program will send an interrupt signal to each
thread. When the interrupt signal reaches the "Java2D Disposer" thread,
a run-time exception occurs forcing the application to terminate.
The following list shows you the output of my program:
Active thread = main
Active thread = AWT-Windows
Active thread = AWT-Shutdown
Active thread = AWT-EventQueue-0
Active thread = Java2D Disposer
Interrupting thread = AWT-Windows
Interrupting thread = AWT-Shutdown
Interrupting thread = AWT-EventQueue-0
Interrupting thread = Java2D Disposer
Exception while removing reference: java.lang.InterruptedException
java.lang.InterruptedException
at java.lang.Object.wait(Native Method)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:111)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:127)
at sun.java2d.Disposer.run(Disposer.java:100)
at java.lang.Thread.run(Thread.java:534)
AWT blocker activation interrupted:
java.lang.InterruptedException
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:429)
at sun.awt.AWTAutoShutdown.activateBlockerThread(AWTAutoShut...
at sun.awt.AWTAutoShutdown.setToolkitBusy(AWTAutoShutdown.ja...
at sun.awt.AWTAutoShutdown.notifyToolkitThreadBusy(AWTAutoSh...
at sun.awt.windows.WToolkit.eventLoop(Native Method)
at sun.awt.windows.WToolkit.run(WToolkit.java:262)
at java.lang.Thread.run(Thread.java:534)
Note 1: Swing (AWT) system uses 4 threads: AWT-Windows, AWT-Shutdown, AWT-EventQueue-0,
and Java2D Disposer.
Note 2: When thread "Java2D Disposer" is interrupted, the entire application terminates.
Sample programs listed in this section have been tested with JDK 1.3.1, 1.4.1, and 1.5.0.
