java - 如何将线程行为限制为调用它们的方法？

Question

考虑这个示例类:

public class Multithreading extends Thread {
    static int i = 0;

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

        call1();
        call2();
    }

    private static void call2() {

        Multithreading call2obj1 = new Multithreading() {
            public void run() {

            }
        };
        call2obj1.start();

    }

    private static void call1() {

        Multithreading call1obj1 = new Multithreading() {
            public void run() {
                System.out.println("call1obj1");
                sleep(5000);
            }
        };
        Multithreading call1obj2 = new Multithreading() {
            public void run() {
                System.out.println("call1obj2");
                sleep(5000);
            }
        };
        call1obj1.start();
        call1obj2.start();

    }
}

我想要的是 call2() 等待 call1() 完全完成。即，call1obj2 不需要等到 call1obj1 执行完毕，但 call2obj1 应该等到 call1obj1 和 >call1obj2 已完成。

基本上，call1obj1 和 call1obj2 的线程行为必须限制为 call1();

这可能吗？

Answer 1

这是使用 CountDownLatch 的解决方案:

public class Multithreading extends Thread {
static int i = 0;

private static CountDownLatch LATCH;

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

    // Initialize the latch with the number of threads to finish
    LATCH = new CountDownLatch(2);

    call1();

    // Main thread will wait until all thread finished
    LATCH.await();

    call2();
}

private static void call2() {

    Multithreading call2obj1 = new Multithreading() {
        public void run() {
            System.out.println("call2obj1");
        }
    };
    call2obj1.start();

}

private static void call1() {

    Multithreading call1obj1 = new Multithreading() {
        public void run() {
            System.out.println("call1obj1");
            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                LATCH.countDown();
            }
        }
    };
    Multithreading call1obj2 = new Multithreading() {
        public void run() {
            System.out.println("call1obj2");
            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                LATCH.countDown();
            }
        }
    };
    call1obj1.start();
    call1obj2.start();

}

}