在java中同步两个线程

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我的java程序中有两个线程，一个是主线程，另一个线程是在主线程中产生的线程A.现在我希望主线程启动线程 A 并等待线程 A 在 run 方法中执行了其部分代码，并且线程 A 应该挂起自己.然后主线程应该开始运行，运行几行代码，然后线程 A 应该从它停止的地方开始，反之亦然.这应该发生 n 次.我正在尝试如下:

I have two threads in my java programme, one is main thread and other thread is thread A which is spawned in main thread. now i want main thread to start thread A and wait till thread A has executed some part of its code in run method and thread A should suspend itself. main thread should then start running, run few lines of code and then again thread A should start from where it has stopped and vice versa. this should happen for n number of times. I am trying as belows:

线程A类:

public class ThreadA implements Runnable { boolean suspended = false; boolean stopped = false; synchronized void stop() { stopped = true; suspended = false; notify(); } synchronized void suspend() { suspended = true; } synchronized void resume() { suspended = false; notify(); } void job() throws InterruptedException { for (int i = 0; i < 5; i++) synchronized (this) { System.out.println("performing job."); suspend(); while (suspended) { notify(); suspended = false; } } } @Override public void run() { try { job(); } catch (InterruptedException e) { e.printStackTrace(); } } }

主线程:

public class MainThread { public static void main(String[] args) throws InterruptedException { ThreadA a1=new ThreadA(); Thread t1=new Thread(a1); synchronized (t1) { t1.start(); for (int i = 0; i < 5; i++) { t1.wait(); System.out.println("perform some action"); a1.resume(); } } } }

预期输出:

performing job. perform some action performing job. perform some action performing job. perform some action performing job. perform some action performing job. perform some action

实际输出:

performing job. performing job. performing job. performing job. performing job. perform some action

即使我在作业方法中发出了 notify() 信号，我也不知道为什么整个 for 循环会在线程 A 中执行.

I don't know why the whole for loop is getting executed in Thread A even when i've issued a notify() signal in job method.

推荐答案

这里有更简单的方法

public class TwoThread { public static void main(String[] args) throws InterruptedException { ThreadA a1 = new ThreadA(); Thread t1 = new Thread(a1); synchronized (a1) { t1.start(); for (int i = 0; i < 5; i++) { a1.wait(); System.out.println("perform some action " + i); a1.notify(); } } } } public class ThreadA implements Runnable { boolean suspended = false; boolean stopped = false; void job() throws InterruptedException { for (int i = 0; i < 5; i++) synchronized (this) { System.out.println("performing job. " + i); notify(); wait(); } } public void run() { try { job(); } catch (InterruptedException e) { e.printStackTrace(); } } }