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/*
* Output:
New thread: Thread[One,5,Group A]
New thread: Thread[Two,5,Group A]
One: 5
New thread: Thread[Three,5,Group B]
New thread: Thread[Four,5,Group B]
Here is output from list():
java.lang.ThreadGroup[name=Group A,maxpri=10]
Thread[One,5,Group A]
Thread[Two,5,Group A]
java.lang.ThreadGroup[name=Group B,maxpri=10]
Thread[Three,5,Group B]
Thread[Four,5,Group B]
Suspending Group A
Three: 5
Two: 5
Four: 5
Resuming Group A
Four: 4
Three: 4
Waiting for threads to finish.
Two: 4
*/
class MyThread extends Thread {
boolean suspended;
MyThread(String threadname, ThreadGroup tgOb) {
super(tgOb, threadname);
System.out.println("New thread: " + this);
suspended = false;
start(); // Start the thread
}
public void run() {
try {
for (int i = 5; i > 0; i--) {
System.out.println(getName() + ": " + i);
Thread.sleep(1000);
synchronized (this) {
while (suspended) {
wait();
}
}
}
} catch (Exception e) {
System.out.println("Exception in " + getName());
}
System.out.println(getName() + " exiting.");
}
void suspendMe() {
suspended = true;
}
synchronized void resumeMe() {
suspended = false;
notify();
}
}
public class MainClass {
public static void main(String args[]) {
ThreadGroup groupA = new ThreadGroup("Group A");
ThreadGroup groupB = new ThreadGroup("Group B");
MyThread ob1 = new MyThread("One", groupA);
MyThread ob2 = new MyThread("Two", groupA);
MyThread ob3 = new MyThread("Three", groupB);
MyThread ob4 = new MyThread("Four", groupB);
System.out.println("\nHere is output from list():");
groupA.list();
groupB.list();
System.out.println("Suspending Group A");
Thread tga[] = new Thread[groupA.activeCount()];
groupA.enumerate(tga); // get threads in group
for (int i = 0; i < tga.length; i++) {
((MyThread) tga[i]).suspendMe(); // suspend each thread
}
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
System.out.println("Main thread interrupted.");
}
System.out.println("Resuming Group A");
for (int i = 0; i < tga.length; i++) {
((MyThread) tga[i]).resumeMe();
}
try {
System.out.println("Waiting for threads to finish.");
ob1.join();
ob2.join();
ob3.join();
ob4.join();
} catch (Exception e) {
System.out.println("Exception in Main thread");
}
System.out.println("Main thread exiting.");
}
}
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