The code example which can prove “volatile” declare should be used

Question

Currently I can\'t understand when we should use volatile to declare variable.

I have do some study and searched some materials about it for a long time

Answer 1

A minimalist example in java 8, if you remove volatile keyword it will never end.

public class VolatileExample {

    private static volatile boolean BOOL = true;

    public static void main(String[] args) throws InterruptedException {
        new Thread(() -> { while (BOOL) { } }).start();
        TimeUnit.MILLISECONDS.sleep(500);
        BOOL = false;
    }
}