尚硅谷JUC#线程按序交替

要求：编写一个程序，开启 3 个线程，这三个线程的 ID 分别为 A、B、C，每个线程将自己的 ID 在屏幕上打印，要 求输出的结果必须按顺序显示。 如：ABCABCABC…… 或ABBCCCABBCCC…依次递归

public class TestABCAlternate {
	
	public static void main(String[] args) {
		AlternateDemo ad = new AlternateDemo();
		
		new Thread(new Runnable() {
			@Override
			public void run() {
				
				for (int i = 1; i <= 20; i++) {
					ad.loopA(i);
				}
				
			}
		}, "A").start();
		
		new Thread(new Runnable() {
			@Override
			public void run() {
				
				for (int i = 1; i <= 20; i++) {
					ad.loopB(i);
				}
				
			}
		}, "B").start();
		
		new Thread(new Runnable() {
			@Override
			public void run() {
				
				for (int i = 1; i <= 20; i++) {
					ad.loopC(i);
					
					System.out.println("-----------------------------------");
				}
				
			}
		}, "C").start();
	}

}

class AlternateDemo{
	
	private int number = 1; //当前正在执行线程的标记
	
	private Lock lock = new ReentrantLock();
	private Condition condition1 = lock.newCondition();
	private Condition condition2 = lock.newCondition();
	private Condition condition3 = lock.newCondition();
	
	/**
	 * @param totalLoop : 循环第几轮
	 */
	public void loopA(int totalLoop){
		lock.lock();
		
		try {
			//1. 判断
			if(number != 1){
				condition1.await();   //线程A等待
			}
			
			//2. 打印
			for (int i = 1; i <= 1; i++) {
				System.out.println(Thread.currentThread().getName() + "\t" + i + "\t" + totalLoop);
			}
			
			//3. 唤醒
			number = 2;
			condition2.signal();  //唤醒B线程
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			lock.unlock();
		}
	}
	
	public void loopB(int totalLoop){
		lock.lock();
		
		try {
			//1. 判断
			if(number != 2){
				condition2.await();		//线程B等待
			}
			
			//2. 打印
			for (int i = 1; i <= 1; i++) {
				System.out.println(Thread.currentThread().getName() + "\t" + i + "\t" + totalLoop);
			}
			
			//3. 唤醒
			number = 3;
			condition3.signal();		//唤醒C线程
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			lock.unlock();
		}
	}
	
	public void loopC(int totalLoop){
		lock.lock();
		
		try {
			//1. 判断
			if(number != 3){
				condition3.await();		//C线程等待
			}
			
			//2. 打印
			for (int i = 1; i <= 1; i++) {
				System.out.println(Thread.currentThread().getName() + "\t" + i + "\t" + totalLoop);
			}
			
			//3. 唤醒
			number = 1;
			condition1.signal();		//唤醒A线程
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			lock.unlock();
		}
	}
	
}