public class WhileTest {
    private boolean flag = true;
    public void setFlag(boolean flag) {
        this.flag = flag;
    }
    public void say() {
        while(flag) {
        }
        System.out.println("--------------线程停止------------------------------------");
    }
    public static void main(String[] args) throws InterruptedException {
        final WhileTest wt = new WhileTest();
        Thread t = new Thread(new Runnable() {
            
            @Override
            public void run() {
                wt.say();
            }
        });
        t.start();
        Thread.currentThread().sleep(500);
        wt.setFlag(false);
    }
}

public void say() {
        while(flag) {
            System.out.println("");
        }
        System.out.println("--------------线程停止------------------------------------");
    }

 public void println(String x) {
        synchronized (this) {
            print(x);
            newLine();
        }
    }