序言

以前看过多线程交替打印奇偶数，知道大概怎么写，实际写的时候会卡住，特此记录下来

方法一：wait, notify，性能较差，不推荐使用

public class TestThread {
    public static int i = 1;

    public static final int TOTAL = 100;

    public static Object lock = new Object();

    public static void main(String[] args) {
        Thread thread1 = new Thread(() -> {
            while (i <= TOTAL) {
                synchronized (lock) {
                    if (i % 2 == 1) {
                        System.out.println("i=" + i++);
                        lock.notify();
                    } else {
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        });

        Thread thread2 = new Thread(() -> {
            while (i <= TOTAL) {
                synchronized (lock) {
                    if (i % 2 == 0) {
                        System.out.println("i=" + i++);
                        lock.notify();
                    } else {
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        });

        thread1.start();
        thread2.start();
    }
}

方法二：countDownLatch，推荐使用

public class TestThread2 {
    private static AtomicInteger num = new AtomicInteger(1);

    private static CountDownLatch countDownLatch = new CountDownLatch(2);

    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread() {
            @Override
            public void run() {
                while (num.intValue() < 100) {
                    if (num.intValue() % 2 == 1) {
                        System.out.println("奇数线程:"+num.intValue());
                        num.incrementAndGet();
                    }
                    countDownLatch.countDown();
                }
            }
        };

        Thread t2 = new Thread() {
            @Override
            public void run() {
                while (num.intValue() <= 100) {
                    if (num.intValue() % 2 == 0) {
                        System.out.println("偶数线程:"+num.intValue());
                        num.incrementAndGet();
                    }
                    countDownLatch.countDown();
                }
            }
        };

        t1.start();
        t2.start();
        countDownLatch.await();
    }
}