ThreadGroup Sample in Java
By: Mashoud Printer Friendly Format
// Demonstrate thread groups.
class NewThread extends Thread {
boolean suspendFlag;
NewThread(String threadname, ThreadGroup tgOb) {
super(tgOb, threadname);
System.out.println("New thread: " + this);
suspendFlag = false;
start(); // Start the thread
}
// This is the entry point for thread.
public void run() {
try {
for(int i = 5; i > 0; i—) {
System.out.println(getName() + ": " + i);
Thread.sleep(1000);
synchronized(this) {
while(suspendFlag) {
wait();
}
}
}
} catch (Exception e) {
System.out.println("Exception in " + getName());
}
System.out.println(getName() + " exiting.");
}
void mysuspend() {
suspendFlag = true;
}
synchronized void myresume() {
suspendFlag = false;
notify();
}
}
class ThreadGroupDemo {
public static void main(String args[]) {
ThreadGroup groupA = new ThreadGroup("Group A");
ThreadGroup groupB = new ThreadGroup("Group B");
NewThread ob1 = new NewThread("One", groupA);
NewThread ob2 = new NewThread("Two", groupA);
NewThread ob3 = new NewThread("Three", groupB);
NewThread ob4 = new NewThread("Four", groupB);
System.out.println("\\nHere is output from list():");
groupA.list();
groupB.list();
System.out.println();
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++) {
((NewThread)tga[i]).mysuspend(); // suspend each thread
}
try {
Thread.sleep(4000);
} catch (InterruptedException e) {
System.out.println("Main thread interrupted.");
}
System.out.println("Resuming Group A");
for(int i = 0; i < tga.length; i++) {
((NewThread)tga[i]).myresume(); // resume threads in group}
// wait for threads to finish
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.");
}
}
Sample output from this program is shown here:
New thread: Thread[One,5,Group A]
New thread: Thread[Two,5,Group A]
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
Four: 5
Three: 4
Four: 4
Three: 3
Four: 3
Three: 2
Four: 2
Resuming Group A
Waiting for threads to finish.
One: 5
Two: 5
Three: 1
Four: 1
One: 4
Two: 4
Three exiting.
Four exiting.
One: 3
Two: 3
One: 2
Two: 2
One: 1
Two: 1
One exiting.
Two exiting.
Main thread exiting.
Inside the program, notice that thread group A is suspended for
four seconds. As the output confirms, this causes threads One and Two to pause, but
threads Three and Four continue running. After the four seconds, threads One and Two
are resumed. Notice how thread group A is suspended and resumed. First, the threads in
group A are obtained by calling enumerate(
) on group A. Then, each
thread is suspended by iterating through the resulting array. To resume the threads in A, the list is again
traversed and each thread is resumed. One last point: this example uses the recommended Java
2 approach to suspending and resuming threads. It does not rely upon the
deprecated methods
suspend( ) and
resume( ).
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Archived Comments
1. The following line in the code
((NewThread)
View Tutorial By: Carlos at 2009-11-18 14:34:51
2. WHY You are using such huge code for suspending an
View Tutorial By: pavan kurariya at 2010-01-14 00:35:55
3. Why not a simple array list of threads?
wha
View Tutorial By: Ranadheer Machineni at 2011-08-18 12:30:35
4. Article from Java Complete Reference
View Tutorial By: venkatesh at 2013-06-04 01:29:02
5. Kindly write organized code so that it can be bene
View Tutorial By: Ravi at 2016-06-06 12:15:15
6. aluetafimen
View Tutorial By: aluetafimen at 2017-06-19 13:05:47
7. equxdaesuij
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8. iturnixiwod
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9. uyigivuxoduv
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10. Hello blogger, do you monetize your java-samples.c
View Tutorial By: Arnulfo1979 at 2017-07-22 05:37:32