要求

开启3个线程，ID分别为A,B,C，每个线程将自己的ID在屏幕上打印10遍，要求输出的结果必须按顺序显示

public class TestABCAlternate {
    public static void main(String[] args) {
        AlternateDemo ad = new AlternateDemo();
        new Thread(new Runnable() {
            @Override
            public void run() {
                // TODO Auto-generated method stub
                for (int i = 0; i < 20; i++) {
                    ad.loopA(i);
                }
            }
        }, "A").start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                // TODO Auto-generated method stub
                for (int i = 0; i < 20; i++) {
                    ad.loopB(i);
                }
            }
        }, "B").start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                // TODO Auto-generated method stub
                for (int i = 0; i < 20; i++) {
                    ad.loopC(i);
                }
            }
        }, "C").start();
    }
}

class AlternateDemo {
    private int number = 1; // 当前正在执行线程的标记

    private Lock lock = new ReentrantLock();//使用lock方式进行加锁
    private Condition condition1 = lock.newCondition();
    private Condition condition2 = lock.newCondition();
    private Condition condition3 = lock.newCondition();

    public void loopA(int totalLoop) {
        lock.lock();
        try {
            if (number != 1) {
                condition1.await();
            }
            for (int i = 1; i <= 5; i++) {//改变循环次数
                System.out.println(Thread.currentThread().getName() + "\t" + i
                        + "\t" + totalLoop);
            }
            number = 2;
            condition2.signal();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public void loopB(int totalLoop) {
        lock.lock();
        try {
            if (number != 2) {
                condition2.await();
            }
            for (int i = 1; i <= 15; i++) {
                System.out.println(Thread.currentThread().getName() + "\t" + i
                        + "\t" + totalLoop);
            }
            number = 3;
            condition3.signal();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public void loopC(int totalLoop) {
        lock.lock();
        try {
            if (number != 3) {
                condition3.await();
            }
            for (int i = 1; i <= 20; i++) {
                System.out.println(Thread.currentThread().getName() + "\t" + i
                        + "\t" + totalLoop);
            }
            number = 1;
            condition1.signal();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
}