I expect infinite loop,but not,why？

Question

code like this

for test two case

one is have volatile keywords ,can stop

other is without volatile,the thread infinite loop

public class VolatileTest extends Thread {

    public boolean flag = false;

    public static void main(String[] args) throws InterruptedException {
        VolatileTest volatileTest = new VolatileTest();
        volatileTest.start();
        Thread.sleep(1000);
        volatileTest.flag = true;
    }

    @Override
    public void run() {
        while (!flag) {
            System.out.println("=====>");
        }
    }
}

Answer 1

My mistake. The problem is that you are calling a synchronized method inside your while loop. Try it like this. Stopped will never print unless you redeclare flag as volatile.

public class VolatileTest extends Thread {

    public boolean flag = false;

    public static void main(String[] args) throws InterruptedException {
        VolatileTest volatileTest = new VolatileTest();
        volatileTest.start();
        Thread.sleep(1000);
        volatileTest.flag = true;
        System.out.println("flag is now " + flag);
         
    }

    @Override
    public void run() {
        int i = 0;
        while (!flag) {
            i++;
        }
        System.out.println("stopped");
    }
}