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Java ThreadGroup list() method with example

ThreadGroup Class list() method: Here, we are going to learn about the list() method of ThreadGroup Class with its syntax and example.
Submitted by Preeti Jain, on December 24, 2019

ThreadGroup Class list() method

• list() method is available in java.lang package.
• list() method is used to list or display information (like name, priority, thread group, etc.) to the standard output about this thread group.
• list() 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.
• list() method does not throw an exception at the time of displaying information about this thread group.

Syntax:

    public void list();

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 list() method of ThreadGroup 

public class ListThreadGroup implements Runnable {
    public static void main(String[] args) {
        ListThreadGroup list_tg = new ListThreadGroup();
        list_tg.listTG();
    }

    public void listTG() {
        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 list() method is to
            // list the contents of the
            // thread group to the std. output
            System.out.println("base.list() :");
            base.list();

            System.out.println();

            System.out.println("derived.list() :");
            derived.list();

            // 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.....

base.list() :
Thread-1 ends.....
java.lang.ThreadGroup[name=Base ThreadGroup,maxpri=10]
    java.lang.ThreadGroup[name=Derived ThreadGroup,maxpri=10]

derived.list() :
java.lang.ThreadGroup[name=Derived ThreadGroup,maxpri=10]