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Java ThreadGroup getParent() method with example

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

ThreadGroup Class getParent() method

• getParent() method is available in java.lang package.
• getParent() method is used to return the parent of this thread group.
• getParent() 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.
• getParent() method may throw an exception at the time of returning parent of this ThreadGroup.
  SecurityException – This exception may throw when the current thread is not permitted to update this Thread group.

Syntax:

    public final ThreadGroup getParent();

Parameter(s):

• It does not accept any parameter.

Return value:

The return type of this method is ThreadGroup – it returns the parent of this "ThreadGroup" or it returns null when there is no parent of this thread group.

Example:

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

public class GetParent implements Runnable {
    public static void main(String[] args) {
        GetParent gp = new GetParent();
        gp.parent();
    }

    public void parent() {
        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 getParent() method is to return the
            // parent of the base and derived thread group

            System.out.println("base.getParent():" + " " + base.getParent().getName());
            System.out.println("derived.getParent():" + " " + derived.getParent().getName());


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

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

        } 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.....
base.getParent(): main
derived.getParent(): Base ThreadGroup