线程间各种操作

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1、两个线程依次执行

private static void demo2() {
    Thread A = new Thread(new Runnable() {
        @Override
        public void run() {
            printNumber("A");
        }
    });

    Thread B = new Thread(new Runnable() {
        @Override
        public void run() {
            System.out.println("B 开始等待 A");
            try {
                A.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            printNumber("B");
        }
    });

    B.start();
    A.start();
}

2、两个线程按照指定方式有序交叉运行

/**
 * A 1, B 1, B 2, B 3, A 2, A 3
 */
private static void demo3() {
    Object lock = new Object();

    Thread A = new Thread(new Runnable() {
        @Override
        public void run() {
            synchronized (lock) {
                System.out.println("A 1");
                try {
                    lock.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                System.out.println("A 2");
                System.out.println("A 3");
            }

        }
    });

    Thread B = new Thread(new Runnable() {
        @Override
        public void run() {
            synchronized (lock) {
                System.out.println("B 1");
                System.out.println("B 2");
                System.out.println("B 3");

                lock.notify();
            }
        }
    });

    A.start();
    B.start();
}

3、四个线程 A B C D，其中 D 要等到 A B C 全执行完毕后才执行，而且 A B C 是异步执行

private static void runDAfterABC() {
    int worker = 3;
    CountDownLatch countDownLatch = new CountDownLatch(worker);

    new Thread(new Runnable() {
        @Override
        public void run() {
            System.out.println("D is waiting for other three threads");
            try {
                countDownLatch.await();
                System.out.println("All done, D starts working");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

        }
    }).start();

    for (char threadName='A'; threadName <= 'C'; threadName++) {
        final String tN = String.valueOf(threadName);
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println(tN + "is working");
                try {
                    Thread.sleep(100);
                } catch (Exception e) {
                    e.printStackTrace();
                }

                System.out.println(tN + "finished");
                countDownLatch.countDown();
            }
        }).start();
    }
}