同步模式之顺序控制，如何控制三个线程依次输出： abc abc abc abc abc？

1.通过 synchronized wait notifyAll 控制三个线程 依次输出 abc abc abc abc abc

	private static Thread t1, t2, t3;
	
	// 用于控制当前哪一个线程执行, state = 0时 t1线程执行， state = 1时 t2线程执行，state = 2时 t3线程执行
    private static int state = 0;

	@Test
    public void test3() throws InterruptedException {
        t1 = new Thread(() -> {
            synchronized (lock) {
                for (int i = 0; i < 5; i++) {
                    while (state != 0) {
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            throw new RuntimeException(e);
                        }
                    }
                    log.info("---------------" + i + "-------------------");
                    log.info("a");
                    state = 1;
                    lock.notifyAll();
                }
            }
        });

        t2 = new Thread(() -> {
            synchronized (lock) {
                for (int i = 0; i < 5; i++) {
                    while (state != 1) {
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            throw new RuntimeException(e);
                        }
                    }
                    log.info("b");
                    state = 2;
                    lock.notifyAll();
                }
            }
        });

        t3 = new Thread(() -> {
            synchronized (lock) {
                for (int i = 0; i < 5; i++) {
                    while (state != 2) {
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            throw new RuntimeException(e);
                        }
                    }
                    log.info("c");
                    state = 0;
                    lock.notifyAll();
                }
            }
        });

        t1.start();
        t2.start();
        t3.start();

        t1.join();
        t2.join();
        t3.join();

    }

2.通过 ReenTrantLock 控制三个线程 依次输出 abc abc abc abc abc

	
	private static Thread t1, t2, t3;

    // 用于控制当前哪一个线程执行, state = 0时 t1线程执行， state = 1时 t2线程执行，state = 2时 t3线程执行
    private static int state = 0;

    private static final Lock reentrantLock = new ReentrantLock();

    private static final Condition[] conditions = new Condition[3];
	
	@Test
    public void test4() throws InterruptedException {
        for (int i = 0; i < 3; i++) {
            conditions[i] = reentrantLock.newCondition();
        }

        Thread t1 = new Thread(() -> {
            reentrantLock.lock();
            try {
                for (int i = 0; i < 5; i++) {
                    while (state != 0) {
                        conditions[0].await();
                    }
                    log.info("---------------" + i + "-------------------");
                    log.info("a");
                    state = 1;
                    conditions[1].signal();
                }
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            } finally {
                reentrantLock.unlock();
            }
        });

        Thread t2 = new Thread(() -> {
            reentrantLock.lock();
            try {
                for (int i = 0; i < 5; i++) {
                    while (state != 1) {
                        conditions[1].await();
                    }
                    log.info("b");
                    state = 2;
                    conditions[2].signal();
                }
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            } finally {
                reentrantLock.unlock();
            }
        });

        Thread t3 = new Thread(() -> {
            reentrantLock.lock();
            try {
                for (int i = 0; i < 5; i++) {
                    while (state != 2) {
                        conditions[2].await();
                    }
                    log.info("c");
                    state = 0;
                    conditions[0].signal();
                }
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            } finally {
                reentrantLock.unlock();
            }
        });

        t1.start();
        t2.start();
        t3.start();

        t1.join();
        t2.join();
        t3.join();

    }

3.通过 park unpark 控制三个线程 依次输出 abc abc abc abc abc

	
	private static Thread t1, t2, t3;

	@Test
    public void test5() throws InterruptedException {

        t1 = new Thread(() -> {
            for (int i = 0; i < 5; i++) {
                log.info("---------------" + i + "-------------------");
                log.info("a");
                LockSupport.unpark(t2);
                LockSupport.park();
            }
        });

        t2 = new Thread(() -> {
            for (int i = 0; i < 5; i++) {
                LockSupport.park();
                log.info("b");
                LockSupport.unpark(t3);
            }
        });

        t3 = new Thread(() -> {
            for (int i = 0; i < 5; i++) {
                LockSupport.park();
                log.info("c");
                LockSupport.unpark(t1);
            }
        });

        t1.start();
        t2.start();
        t3.start();

        t1.join();
        t2.join();
        t3.join();

    }