Java - ThreadGroup parentOf() Method with Examples

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Description

The Java ThreadGroup parentOf() method 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 1

The following example shows the usage of ThreadGroup parentOf() method in case of multiple ThreadGroup objects. We've created a parent ThreadGroup object and assigned it a name. As next, we've created a child ThreadGroup object. Then we've created two threads using the threadgroup objects created earlier. Using parentOf() method, we're printing checking of parent of child threadgroup object.

package com.tutorialspoint;

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

   public void start() {
      try {     
         // create a parent ThreadGroup
         ThreadGroup pThreadGroup = new ThreadGroup("parent ThreadGroup");
		 
         // create a child ThreadGroup for parent ThreadGroup
         ThreadGroup cThreadGroup = new ThreadGroup(pThreadGroup, "child ThreadGroup");

         // create a thread
         Thread t1 = new Thread(pThreadGroup, this);
         System.out.println("Starting " + t1.getName() + "...");
         t1.start();
            
         // create another thread
         Thread t2 = new Thread(cThreadGroup, this);
         System.out.println("Starting " + t2.getName() + "...");
         t2.start();

         // determine which ThreadGroup is parent
         boolean isParent = pThreadGroup.parentOf(cThreadGroup);
         System.out.println(pThreadGroup.getName() + " is the parent of "
            + cThreadGroup.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 < 4;i++) {
         i++;
         try {
			Thread.sleep(50);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
      }
      System.out.println(Thread.currentThread().getName() + " finished executing.");
   }
} 

Output

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

Starting Thread-0...
Starting Thread-1...
parent ThreadGroup is the parent of child ThreadGroup? true
Thread-1 finished executing.
Thread-0 finished executing.

Example 2

The following example shows the usage of ThreadGroup parentOf() method in case of multiple ThreadGroup objects. We've created a parent ThreadGroup object and assigned it a name. As next, we've created a child ThreadGroup object. Then we've created two threads using the threadgroup objects created earlier. Using parentOf() method, we're printing checking of parent of parent threadgroup object.

package com.tutorialspoint;

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

   public void start() {
      try {     
         // create a parent ThreadGroup
         ThreadGroup pThreadGroup = new ThreadGroup("parent ThreadGroup");
		 
         // create a child ThreadGroup for parent ThreadGroup
         ThreadGroup cThreadGroup = new ThreadGroup(pThreadGroup, "child ThreadGroup");

         // create a thread
         Thread t1 = new Thread(pThreadGroup, this);
         System.out.println("Starting " + t1.getName() + "...");
         t1.start();
            
         // create another thread
         Thread t2 = new Thread(cThreadGroup, this);
         System.out.println("Starting " + t2.getName() + "...");
         t2.start();

         // determine which ThreadGroup is parent
         boolean isParent = cThreadGroup.parentOf(pThreadGroup);
         System.out.println(cThreadGroup.getName() + " is the parent of "
            + pThreadGroup.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 < 4;i++) {
         i++;
         try {
			Thread.sleep(50);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
      }
      System.out.println(Thread.currentThread().getName() + " finished executing.");
   }
} 

Output

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

Starting Thread-0...
Starting Thread-1...
child ThreadGroup is the parent of parent ThreadGroup? false
Thread-1 finished executing.
Thread-0 finished executing.

Example 3

The following example shows the usage of ThreadGroup parentOf() method in case of child and grandchild ThreadGroup objects. We've created a ThreadGroup object and assigned it a name. As next, we've created a child ThreadGroup object. Then we've created two threads using the child and grandchild threadgroup objects created earlier. Using parentOf() method, we're printing name of the parent of each threadgroup object.

package com.tutorialspoint;

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

   public void start() {
      try {     
         // create a parent ThreadGroup
         ThreadGroup pThreadGroup = new ThreadGroup("parent ThreadGroup");
		 
         // create a child ThreadGroup for parent ThreadGroup
         ThreadGroup cThreadGroup = new ThreadGroup(pThreadGroup, "child ThreadGroup");
		 
         // create a grandchild ThreadGroup for child ThreadGroup
         ThreadGroup gThreadGroup = new ThreadGroup(cThreadGroup, "grandchild ThreadGroup");

         // create a thread
         Thread t1 = new Thread(cThreadGroup, this);
         System.out.println("Starting " + t1.getName() + "...");
         t1.start();
            
         // create another thread
         Thread t2 = new Thread(gThreadGroup, this);
         System.out.println("Starting " + t2.getName() + "...");
         t2.start();

         // determine which ThreadGroup is parent
         boolean isParent = pThreadGroup.parentOf(cThreadGroup);
         System.out.println(pThreadGroup.getName() + " is the parent of "
            + cThreadGroup.getName() + "? " + isParent);
			
         isParent = pThreadGroup.parentOf(gThreadGroup);
         System.out.println(pThreadGroup.getName() + " is the parent of "
            + gThreadGroup.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 < 4;i++) {
         i++;
         try {
			Thread.sleep(50);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
      }
      System.out.println(Thread.currentThread().getName() + " finished executing.");
   }
} 

Output

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

Starting Thread-0...
Starting Thread-1...
parent ThreadGroup is the parent of child ThreadGroup? true
parent ThreadGroup is the parent of grandchild ThreadGroup? true
Thread-1 finished executing.
Thread-0 finished executing.