多线程轮流打印a，b，c

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

public class PrintABC {
    private static Lock lock = new ReentrantLock();
    private static Condition conditionA = lock.newCondition();
    private static Condition conditionB = lock.newCondition();
    private static Condition conditionC = lock.newCondition();
    private static int count = 0;

    public static void main(String[] args) {
        Thread threadA = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                print("A", conditionA, conditionB);
            }
        });

        Thread threadB = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                print("B", conditionB, conditionC);
            }
        });

        Thread threadC = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                print("C", conditionC, conditionA);
            }
        });

        threadA.start();
        threadB.start();
        threadC.start();
    }

    private static void print(String str, Condition current, Condition next) {
        lock.lock();
        try {
            while (count % 3 != 0) {
                current.await();
            }
            System.out.print(str);
            count++;
            next.signal();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
}

在这个示例中，我们使用了ReentrantLock和Condition来实现线程之间的协作。每个线程在打印自己的字符后，会唤醒下一个线程，并等待自己的下一个轮次。通过这种方式，三个线程可以轮流打印出"abcabcabc..."这样的字符串。