Java.lang.ThreadGroup.parentOf() Method

Description

The java.lang.ThreadGroup.parentOf() method tests if this thread group is either the thread group argument or one of its ancestor thread groups.

Declaration

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

public final boolean parentOf(ThreadGroup g)

Parameters

• g -- This is a thread group.

Return Value

This method returns true if this thread group is the thread group argument or one of its ancestor thread groups; false otherwise.

Exception

• NA

Example

The following example shows the usage of java.lang.ThreadGroup.parentOf() 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();
            
         // determine which ThreadGroup is parent
         boolean isParent = pGroup.parentOf(cGroup);
         System.out.println(pGroup.getName() + " is the parent of "
         + cGroup.getName() + "? " + isParent);

         isParent = cGroup.parentOf(pGroup);
         System.out.println(cGroup.getName() + " is the parent of "
         + pGroup.getName() + "? " + isParent);

         // 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...
Thread-0 finished executing.
Parent ThreadGroup is the parent of Child ThreadGroup? true
Child ThreadGroup is the parent of Parent ThreadGroup? false
Thread-1 finished executing.