public class NumberPrint implements Runnable {    private int state = 1;    private int n = 1;    // 使用lock做锁    private ReentrantLock lock = new ReentrantLock();    // 获得lock锁的3个分支条件    private Condition c1 = lock.newCondition();    private Condition c2 = lock.newCondition();    private Condition c3 = lock.newCondition();    @Override    public void run() {        new Thread(new Runnable() {            public void run() {                for (int i = 0; i < 5; i++) {                    try {                        // 线程1获得lock锁后, 其他线程将无法进入需要lock锁的代码块.                        // 在lock.lock()和lock.unlock()之间的代码相当于使用了synchronized(lock){}                        lock.lock();                        while (state != 1)                            try {                                // 线程1竞争到了lock, 但是发现state不为1, 说明此时还未轮到线程1打印.                                 // 因此线程1将在c1上wait                                // 与解法一不同的是, 三个线程并非在同一个对象上wait, 也不由同一个对象唤醒                                c1.await();                            } catch (InterruptedException e) {                                e.printStackTrace();                            }                        // 如果线程1竞争到了lock, 也通过了state判定, 将执行打印任务                        for (int j = 0; j < 5; j++) {                            System.out.println(Thread.currentThread().getName()                                    + ": " + n++);                        }                        System.out.println();                        // 打印完成后将state赋值为2, 表示下一次的打印任务将由线程2执行                        state = 2;                        // 唤醒在c2分支上wait的线程2                        c2.signal();                    } finally {                        // 打印任务执行完成后需要确保锁被释放, 因此将释放锁的代码放在finally中                        lock.unlock();                    }                }            }        }, "线程1").start();        new Thread(new Runnable() {            public void run() {                for (int i = 0; i < 5; i++) {                    try {                        lock.lock();                        while (state != 2)                            try {                                c2.await();                            } catch (InterruptedException e) {                                e.printStackTrace();                            }                        for (int j = 0; j < 5; j++) {                            System.out.println(Thread.currentThread().getName()                                    + ": " + n++);                        }                        System.out.println();                        state = 3;                        c3.signal();                    } finally {                        lock.unlock();                    }                }            }        }, "线程2").start();        new Thread(new Runnable() {            public void run() {                for (int i = 0; i < 5; i++) {                    try {                        lock.lock();                        while (state != 3)                            try {                                c3.await();                            } catch (InterruptedException e) {                                e.printStackTrace();                            }                        for (int j = 0; j < 5; j++) {                            System.out.println(Thread.currentThread().getName()                                    + ": " + n++);                        }                        System.out.println();                        state = 1;                        c1.signal();                    } finally {                        lock.unlock();                    }                }            }        }, "线程3").start();    }        public static void main(String[] args) {        new NumberPrint().run();    }}