java中的线程间通信

Question

彼此依赖的线程如何在Java中进行通信？

例如,我正在构建一个带有线程的Web爬虫,这些线程需要来自其他线程的数据.

Answer 1

以下是Inter线程通信的示例:

public class Main {
    public static void main(String[] args) {
        Chat m = new Chat();
        new T1(m);
        new T2(m);
    }
}

class Chat {
    boolean flag = false;

    public synchronized void FromSam(String msg) {
        if (flag) {
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.println(msg);
        flag = true;
        notify();
    }

    public synchronized void FromJam(String msg) {
        if (!flag) {
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        System.out.println(msg);
        flag = false;
        notify();
    }
}

class T1 implements Runnable {
    Chat m;
    String[] s1 = { "Hello Jam", "How are you ?", "I am also doing fine!" };

    public T1(Chat m1) {
        this.m = m1;
        new Thread(this, "Sam").start();
    }

    public void run() {
        for (int i = 0; i < s1.length; i++) {
            m.FromSam(s1[i]);
        }
    }
}

class T2 implements Runnable {
    Chat m;
    String[] s2 = { "HI Sam", "I am good,And U ?", "ha haa" };

    public T2(Chat m2) {
        this.m = m2;
        new Thread(this, "Jam").start();
    }

    public void run() {
        for (int i = 0; i < s2.length; i++) {
            m.FromJam(s2[i]);
        }
    }
}

Answer 2

这取决于沟通的性质.

• 它是双工的(即A与B和B会谈到A)吗？
• 是完成数据的沟通还是沟通？
• 等等.

最简单和最可取的线程间通信形式只是等待其他线程的完成.这通过使用最容易完成Future:

ExecutorService exec = Executors.newFixedThreadPool(50);
final Future f = exec.submit(task1);
exec.submit(new Runnable() {
    @Override
    public void run() {
        f.get();
        // do stuff
    }
});

第二个任务在第一个任务完成之前不会执行.

Java 5+有许多并发实用程序来处理这类事情.这可能意味着使用LinkedBlockingQueues CountDownLatch或许多其他.

要深入研究并发性Java Concurrency in Practice是必读的.