Java实现三个线程进行顺序打印的两种方案

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

public class SequencePrint {
    private final Lock lock = new ReentrantLock();
    private final Condition cond1 = lock.newCondition();
    private final Condition cond2 = lock.newCondition();
    private final Condition cond3 = lock.newCondition();
    private int state = 1; // 当前应该打印的序号

    public void print(String name, int targetState, Condition current, Condition next) {
        for (int i = 0; i < 10; i++) { // 假设打印10轮
            lock.lock();
            try {
                // 如果还没轮到我，就一直等着
                while (state != targetState) {
                    current.await();
                }
                System.out.print(name + " ");
                // 修改状态并唤醒下一个线程
                state = (targetState % 3) + 1;
                next.signal();
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            } finally {
                lock.unlock();
            }
        }
    }

    public static void main(String[] args) {
        SequencePrint sp = new SequencePrint();
        new Thread(() -> sp.print("A", 1, sp.cond1, sp.cond2)).start();
        new Thread(() -> sp.print("B", 2, sp.cond2, sp.cond3)).start();
        new Thread(() -> sp.print("C", 3, sp.cond3, sp.cond1)).start();
    }
}

public class WaitNotifyPrint {
    private int state = 1;
    private final Object lock = new Object();

    public void print(String name, int targetState) {
        for (int i = 0; i < 10; i++) {
            synchronized (lock) {
                while (state != targetState) {
                    try { lock.wait(); } catch (InterruptedException e) {}
                }
                System.out.print(name);
                state = (state % 3) + 1;
                lock.notifyAll(); // 唤醒所有人，让他们竞争判断 state
            }
        }
    }

    public static void main(String[] args) {
        WaitNotifyPrint wnp = new WaitNotifyPrint();
        new Thread(() -> wnp.print("A", 1)).start();
        new Thread(() -> wnp.print("B", 2)).start();
        new Thread(() -> wnp.print("C", 3)).start();
    }
}