三个线程交替打印ABC

public class ABCLock {
    public static void main(String[] args){
        //共用的对象，保证是同个锁
       final PrintABC printABC= new PrintABC();

        new Thread(new Runnable() {
            @Override
            public void run() {
                printABC.printA();
            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                printABC.printC();
            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                printABC.printB();
            }
        }).start();



    }

}

class PrintABC{
    private final ReentrantLock lock = new ReentrantLock();
    //通知打印A的信号
    private Condition printA=lock.newCondition();
    //通知打印B的信号
    private Condition printB=lock.newCondition();
    //通知打印C的信号
    private Condition printC=lock.newCondition();
    //控制打印第一次的打印值
    private  int flag=0;

    public  void printA(){
        for(int i=0;i<5;i++) {
            lock.lock();
            try {
                //循环检测标志，不是0，不发出打印A信号
                while(flag !=0)
                    printA.await();
                System.out.println("A");
                flag=1;
                //发出打印b的信号
                printB.signal();
            } catch (Exception e) {
                e.printStackTrace();
            }finally {
                lock.unlock();
            }
        }
    }

    public  void printB(){
        for(int i=0;i<5;i++) {
            lock.lock();
            try {
                while (flag !=1)
                    printB.await();

                    System.out.println("B");
                    flag=2;
                    printC.signal();
                } catch (Exception e) {
                    e.printStackTrace();
                }finally {
                lock.unlock();
            }

        }
    }

    public  void printC(){
        for(int i=0;i<5;i++) {
            lock.lock();
            try {
                while (flag !=2)
                    printC.await();
                System.out.println("C");
                flag=0;
                printA.signal();
            } catch (Exception e) {
                e.printStackTrace();
            }finally {
                lock.unlock();
            }
        }
    }
}