按照順序列印執行緒A、B、C，共列印五輪：

public class Test {

    public static void main(String[] args) {
        AlternatePrinting printing = new AlternatePrinting();
        new Thread(() -> {
            for (int i = 1; i <= 5; i++) {
                try {
                    printing.method1(i);
                } catch
 
 (Exception e) {
                    e.printStackTrace();
                }
            }
        }, "A").start();

        new Thread(() -> {
            for (int i = 1; i <= 5; i++) {
                try {
                    printing.method2(i);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }, "B"
 
).start();

        new Thread(() -> {
            for (int i = 1; i <= 5; i++) {
                try {
                    printing.method3(i);
                    System.out.println("<------------我是可愛的分割線------------->");
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }, "C"
 
).start();
    }
}

class AlternatePrinting {

    private int number = 1;
    private Lock lock = new ReentrantLock();
    private Condition condition1 = lock.newCondition();
    private Condition condition2 = lock.newCondition();
    private Condition condition3 = lock.newCondition();

    public void method1(int time) throws Exception {
        lock.lock();
        try {
            if (number != 1) {
                    condition1.await();
            }
            System.out.println(Thread.currentThread().getName() + "\t" + time);
            number = 2;
            // 喚醒2
            condition2.signal();
        } finally {
            lock.unlock();
        }
    }

    public void method2(int time) throws Exception {
        lock.lock();
        try {
            if (number != 2) {
                condition2.await();
            }
            System.out.println(Thread.currentThread().getName() + "\t" + time);
            number = 3;
            // 喚醒3
            condition3.signal();
        } finally {
            lock.unlock();
        }
    }

    public void method3(int time) throws Exception {
        lock.lock();
        try {
            if (number != 3) {
                condition3.await();
            }
            System.out.println(Thread.currentThread().getName() + "\t" + time);
            number = 1;
            // 喚醒1
            condition1.signal();
        } finally {
            lock.unlock();
        }
    }
}