Java.lang.ThreadGroup.getParent() Method


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Description

The java.lang.ThreadGroup.getParent() method returns the parent of this thread group.

Declaration

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

public final ThreadGroup getParent()

Parameters

NA

Return Value

This method returns the parent of this thread group. The top-level thread group is the only thread group whose parent is null.

Exception

SecurityException − if the current thread cannot modify this thread group.

Example

The following example shows the usage of java.lang.ThreadGroup.getParent() 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();

         // prints the parent ThreadGroup of both parent and child threads
         System.out.println("ParentThreadGroup for " +
            pGroup.getName() + " is " + pGroup.getParent().getName());
         System.out.println("ParentThreadGroup for " +
            cGroup.getName() + " is " + cGroup.getParent().getName());
         
         // 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.
ParentThreadGroup for Parent ThreadGroup is main
ParentThreadGroup for Child ThreadGroup is Parent ThreadGroup
Thread-1 finished executing.

java_lang_threadgroup.htm

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