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Java ThreadGroup destroy() method with example

ThreadGroup Class destroy() method: Here, we are going to learn about the destroy() method of ThreadGroup Class with its syntax and example.
Submitted by Preeti Jain, on December 23, 2019

ThreadGroup Class destroy() method

• destroy() method is available in java.lang package.
• destroy() method is used to destroy this thread group and when we destroy this thread group so its child thread group will be destroyed simultaneously.
• destroy() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
• destroy() method may throw an exception at the time of destroying this thread group.
  • SecurityException – This exception may throw when the current thread is not permitted to update this thread group.
  • IllegalThreadStateException – This exception may throw in two cases
    • When this thread group has already been destroyed.
    • When this thread group is not blank.

Syntax:

    public final void destroy();

Parameter(s):

• It does not accept any parameter.

Return value:

The return type of this method is void, it returns nothing.

Example:

// Java program to demonstrate the example 
// of void destroy() method of ThreadGroup 

public class Destroy implements Runnable {
    public static void main(String[] args) {
        Destroy des = new Destroy();
        des.destroyed();
    }

    public void destroyed() {
        try {
            // Create two thread group and the named are base
            // and derived

            ThreadGroup base = new ThreadGroup("Base ThreadGroup");
            ThreadGroup derived = new ThreadGroup(base, "Derived ThreadGroup");

            // create two threads
            Thread th1 = new Thread(base, this);
            Thread th2 = new Thread(derived, this);

            //By using getName() method is to retrieve the
            // name of the thread th1
            System.out.println(th1.getName() + " " + "begins.....");

            // By using start() method is to start its execution 
            // of thread th1
            th1.start();

            //By using getName() method is to retrieve the
            // name of the thread th2
            System.out.println(th2.getName() + " " + "begins.....");


            // By using start() method is to start its execution 
            // of thread th2
            th2.start();

            System.out.println();

            // By using join() method is to wait the current
            // thread till complete execution of another
            // thread

            th1.join();
            th2.join();

            // By using destroy() method is to
            // destroy the thread group named derived
            derived.destroy();
            boolean b1 = derived.isDestroyed();
            System.out.println(derived.getName() + " " + "destroyed" + " " + b1);

            boolean b2 = base.isDestroyed();
            System.out.println(base.getName() + " " + "destroyed" + " " + b2);

        } catch (InterruptedException ex) {
            ex.printStackTrace();
        }
    }

    // Override run()
    public void run() {
        for (int k = 0; k < 100; ++k)
            ++k;
        System.out.println(Thread.currentThread().getName() + " " + "ends.....");
    }
}

Output

Thread-0 begins.....
Thread-0 ends.....
Thread-1 begins.....

Thread-1 ends.....
Derived ThreadGroup destroyed true
Base ThreadGroup destroyed false