Question

This code end up with different results if I change the parameter of sleep(), and here is some sample outcomes:

1.sleep(1l), the thread will always terminate automaticlly, the "Stoped" statement will always be printed, and the icon of "Terminate" in Eclipse will be grey too. (seems working perfectly huh?)

2.sleep(1000l), here comes the problem, if main thread sleeps for 1 second, the Thread v will never terminated automaticlly, the "Stoped" will not be printed, and the icon of "Terminate" is red, which means there is still some thread running.

I know it could be solved if I add "volitale" for the parameter "isRunning", but I wonder why and how does the sleep() statement affect the outcome?

PS:I'm a newbie for both java and english, so I apologize for any possible discomforts due to this question.

public class VolitaleTest {

    public static void main(String[] args) throws InterruptedException {

        Vo v = new Vo();
        new Thread(v).start();
        Thread.sleep(1000l);
        v.setRunning(false);
        System.out.println(v.i);
    }
}

class Vo implements Runnable {

    private boolean isRunning = true;
    int i = 0;

    public void run() {
        while (isRunning) {
            i++;
            // System.out.println("Running");
            /*
             * Once you add this statement, you will always be able to terminate
             * the program automatically, no matter how long the thread sleeps.
             */
        }
        System.out.println("Stoped.");
    }

    public void setRunning(boolean isRunning) {
        this.isRunning = isRunning;
    }
}

Answer 1

volatile使得一个线程写入的内容成为可能，包括写入volatile变量，以便在读取该变量时从另一个线程开始可见。如果变量不是volatile那么发生 - 在内存关系无法保证之前。

Different outcome of java multi-thread due to length of sleep()?

1 个答案: