Killing Thread in Java

Thread

A thread is a piece of that executes independently. Every program contains at least one thread I.e. main thread. This thread default name is main only.

Multithreading:

Execution of more than one thread at a time is called as Multithreading.

-A thread will automatically destroyed when the run() method has completed. But it might be require to kill/stop a thread before it has completed its life cycle.

Using a boolean flag: We can define a boolean variable which is used for stopping/killing threads say ‘exit’. Whenever we want to stop a thread, the ‘exit’ variable will be set to true.

class NewThread implements Runnable 
{
    private boolean exit;
    private String name;
    Thread t;

    NewThread(String threadname)
    {
        name = threadname;
        t = new Thread(this, name);
        System.out.println("New thread: " + t);
        exit = false;
        t.start();
    }
    public void run()
    {
        int i = 0;
        while (!exit) 
        {
            System.out.println(name + ": " + i);
            i++;
            try 
            {
                Thread.sleep(100);
            }
            catch (InterruptedException e) 
            {
                System.out.println("Caught:" + e);
            }
        }
        System.out.println(name + " Stopped.");
    }
    public void stop()
    {
        exit = true;
    }
}

public class Main 
{
    public static void main(String args[])
    {
        NewThread t1 = new NewThread("First thread");
        NewThread t2 = new NewThread("Second thread");
        try 
        {
            Thread.sleep(500);
            t1.stop();
            t2.stop();
            Thread.sleep(500);
        }
        catch (InterruptedException e) 
        {
            System.out.println("Caught:" + e);
        }
        System.out.println("Exiting the main Thread");
    }
}

Output:

class MyThread implements Runnable 
{
    Thread t;
    MyThread()
    {
        t = new Thread(this);
        System.out.println("New thread: " + t);
        t.start(); 
    }

    
    public void run()
    {
        while (!Thread.interrupted()) 
        {
            System.out.println("Thread is running");
        }
        System.out.println("Thread has stopped.");
    }
}

public class Main 
{
    public static void main(String args[])
    {
        MyThread t1 = new MyThread();

        try 
        {
            Thread.sleep(1);
            t1.t.interrupt();
            Thread.sleep(5);
        }
        catch (InterruptedException e) 
        {
            System.out.println("Caught:" + e);
        }
        System.out.println("Exiting the main Thread");
    }
}

Output: