Simple switching the flag from other thread that will stop loop in thread

ThreadTest.java

import org.junit.Test;

public class ThreadTest {

    private boolean flag = true;

    @Test
    public void testName() throws Exception {

        new Thread(new Runnable() {
            @Override
            public void run() {
                while(flag) {
                    System.out.println("loop" + System.currentTimeMillis());
                    sleep(100);
                }
            }
        }).start();


        new Thread(new Runnable() {
            @Override
            public void run() {
                sleep(2000);
                System.out.println("cancelling " + System.currentTimeMillis());
                flag = false;
            }
        }).start();

         Thread.sleep(4000);
    }
    
    //this finishes with:

//    loop1397758576907
//    loop1397758577008
//    loop1397758577108
//    cancelling 1397758577204

//    Process finished with exit code 0

    private void sleep(int millis) {
        try {
            Thread.sleep(millis);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}