Java.lang.ThreadGroup.list() Method

Description

The java.lang.ThreadGroup.list() method prints information about this thread group to the standard output. This is useful only for debugging.

Declaration

Following is the declaration for java.lang.ThreadGroup.list() method

public void list()

Parameters

• NA

Return Value

This method does not return any value.

Exception

• NA

Example

The following example shows the usage of java.lang.ThreadGroup.list() method.

package com.tutorialspoint;

import java.lang.*;

public class ThreadGroupDemo implements Runnable
{
   public static void main(String[] args) {
      ThreadGroupDemo tg = new ThreadGroupDemo();
      tg.func();
   }

   public void func() {
      try {     
         // create a parent ThreadGroup
         ThreadGroup pGroup = new ThreadGroup("Parent ThreadGroup");
    
         // create a child ThreadGroup for parent ThreadGroup
         ThreadGroup cGroup = new ThreadGroup(pGroup, "Child ThreadGroup");

         // create a thread
         Thread t1 = new Thread(pGroup, this);
         System.out.println("Starting " + t1.getName() + "...");
         t1.start();
            
         // create another thread
         Thread t2 = new Thread(cGroup, this);
         System.out.println("Starting " + t2.getName() + "...");
         t2.start();
             
         // listing contents of parent ThreadGroup
         System.out.println("\nListing parentThreadGroup: " +
         pGroup.getName() + ":");
         // prints information about this thread group to the standard output
         pGroup.list();

         // listing contents of child ThreadGroup
         System.out.println("\nListing childThreadGroup : " +
         cGroup.getName() + ":");
         // prints information about this thread group to the standard output
         cGroup.list();

         // block until the other threads finish
         t1.join();
         t2.join();
      }
      catch (InterruptedException ex) {
         System.out.println(ex.toString());
      }
   }

   // implements run()
   public void run() {

      for(int i = 0;i < 1000;i++) {
         i++;
      }
      System.out.println(Thread.currentThread().getName() + 
      " finished executing.");
   }
}  

Let us compile and run the above program, this will produce the following result:

Starting Thread-0...
Starting Thread-1...

Listing parentThreadGroup: Parent ThreadGroup:
java.lang.ThreadGroup[name=Parent ThreadGroup,maxpri=10]
    Thread[Thread-0,5,Parent ThreadGroup]
    Thread-1 finished executing.
Thread-0 finished executing.
java.lang.ThreadGroup[name=Child ThreadGroup,maxpri=10]
        Thread[Thread-1,5,Child ThreadGroup]

Listing childThreadGroup : Child ThreadGroup:
java.lang.ThreadGroup[name=Child ThreadGroup,maxpri=10]
    Thread[Thread-1,5,Child ThreadGroup]