Java - ThreadGroup toString() Method with Examples

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Description

The Java ThreadGroup toString() method returns the string representation of this thread group.

Declaration

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

public String toString()

Parameters

NA

Return Value

This method returns returns the string representation of this thread group.

Exception

NA

Example 1

The following example shows the usage of ThreadGroup toString() method in case of a single ThreadGroup object. We've created a ThreadGroup object and assigned it a name. Then we've created two threads using the threadgroup object created earlier. Using toString() method, we're getting the string representation of the thread group 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 ThreadGroup
         ThreadGroup threadGroup = new ThreadGroup("ThreadGroup");

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

         // returns the string representation of thread group
         System.out.println("String representation of threadGroup = " + threadGroup.toString());

         // 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().toString() + " finished executing.");
   }
} 

Output

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

Starting Thread[Thread-0,5,ThreadGroup]...
Starting Thread[Thread-1,5,ThreadGroup]...
String representation of threadGroup = java.lang.ThreadGroup[name=ThreadGroup,maxpri=10]
Thread[Thread-1,5,ThreadGroup] finished executing.
Thread[Thread-0,5,ThreadGroup] finished executing.

Example 2

The following example shows the usage of ThreadGroup toString() method in case of multiple 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 threadgroup objects created earlier. Using toString() method, we're printing string representation of each threadgroup objects.

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

         // returns the string representation of thread groups
         System.out.println("String representation of pThreadGroup = " + pThreadGroup.toString());
         System.out.println("String representation of cThreadGroup = " + cThreadGroup.toString());
         // 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().toString() + " finished executing.");
   }
} 

Output

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

Starting Thread[Thread-0,5,parent ThreadGroup]...
Starting Thread[Thread-1,5,child ThreadGroup]...
String representation of pThreadGroup = java.lang.ThreadGroup[name=parent ThreadGroup,maxpri=10]
String representation of cThreadGroup = java.lang.ThreadGroup[name=child ThreadGroup,maxpri=10]
Thread[Thread-1,5,child ThreadGroup] finished executing.
Thread[Thread-0,5,parent ThreadGroup] finished executing.

Example 3

The following example shows the usage of ThreadGroup toString() 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 toString() method, we're printing string representation 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 parent ThreadGroup
         ThreadGroup gThreadGroup = new ThreadGroup(cThreadGroup, "GrandChild ThreadGroup");

         // create a thread
         Thread t1 = new Thread(cThreadGroup, this);
         System.out.println("Starting " + t1.toString() + "...");
         t1.start();
            
         // create another thread
         Thread t2 = new Thread(gThreadGroup, this);
         System.out.println("Starting " + t2.toString() + "...");
         t2.start();
            
         // returns the string representation of thread groups
         System.out.println("String representation of pThreadGroup = " + pThreadGroup.toString());
         System.out.println("String representation of cThreadGroup = " + cThreadGroup.toString());
         System.out.println("String representation of gThreadGroup = " + gThreadGroup.toString());
		 
         // 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().toString() + " finished executing.");
   }
} 

Output

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

Starting Thread[Thread-0,5,Child ThreadGroup]...
Starting Thread[Thread-1,5,GrandChild ThreadGroup]...
String representation of pThreadGroup = java.lang.ThreadGroup[name=Parent ThreadGroup,maxpri=10]
String representation of cThreadGroup = java.lang.ThreadGroup[name=Child ThreadGroup,maxpri=10]
String representation of gThreadGroup = java.lang.ThreadGroup[name=GrandChild ThreadGroup,maxpri=10]
Thread[Thread-0,5,Child ThreadGroup] finished executing.
Thread[Thread-1,5,GrandChild ThreadGroup] finished executing.