Java如何实现线程排序问题

package com.blithe;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

public class ReentrantLockDemo {

    private static ReentrantLock lock = new ReentrantLock();

    private static Condition cA = lock.newCondition();
    private static Condition cB = lock.newCondition();
    private static Condition cC = lock.newCondition();

    private static CountDownLatch lB = new CountDownLatch(1);
    private static CountDownLatch lC = new CountDownLatch(1);

    /**
     * 存在三个线程cA、cB、cC,三个线程依次打印A、B、C,要求依次输出结果ABCABC
     * @param args
     */
    public static void main(String[] args) {
        new Thread(() ->{
            lock.lock();

            try {
                for (int i = 0; i < 10; i++) {
                    cB.signal();
                    System.out.print("A");
                    // 保证线程执行顺序,由A线程先进行执行
                    if (i == 0) lB.countDown();
                    // 阻塞当前线程
                    cA.await();
                }
                // 保证在所有的程序执行结束的时候,线程不处于await状态
                cB.signal();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }
        }, "threadA").start();

        new Thread(() ->{
            try {
                // 确保如果线程B先执行,则线程进入阻塞状态
                lB.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            lock.lock();

            try {
                for (int i = 0; i < 10; i++) {
                    cC.signal();
                    System.out.print("B");
                    if (i == 0) lC.countDown();
                    cB.await();
                }
                cC.signal();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }, "threadB").start();

        new Thread(() ->{
            try {
                lC.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            lock.lock();

            try {
                for (int i = 0; i < 10; i++) {
                    cA.signal();
                    System.out.print("C");
                    cC.await();
                }
                cA.signal();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }, "threadC").start();
    }
}

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