Java 中 AQS 的几大经典实现示例详解

import java.util.concurrent.locks.ReentrantLock;
public class ReentrantLockExample {
    private final ReentrantLock lock = new ReentrantLock();
    public void safeMethod() {
        lock.lock(); // 获取锁
        try {
            // 临界区代码
            System.out.println("线程安全操作");
        } finally {
            lock.unlock(); // 释放锁
        }
    }
}

import java.util.concurrent.locks.ReentrantReadWriteLock;
public class ReadWriteLockExample {
    private final ReentrantReadWriteLock rwLock = new ReentrantReadWriteLock();
    private int sharedData = 0;
    public void readData() {
        rwLock.readLock().lock(); // 获取读锁
        try {
            System.out.println("读取数据: " + sharedData);
        } finally {
            rwLock.readLock().unlock(); // 释放读锁
        }
    }
    public void writeData(int value) {
        rwLock.writeLock().lock(); // 获取写锁
        try {
            sharedData = value;
            System.out.println("写入数据: " + value);
        } finally {
            rwLock.writeLock().unlock(); // 释放写锁
        }
    }
}

import java.util.concurrent.Semaphore;
public class SemaphoreExample {
    private final Semaphore semaphore = new Semaphore(3); // 允许最多3个线程同时访问
    public void accessResource() throws InterruptedException {
        semaphore.acquire(); // 获取许可证
        try {
            // 访问共享资源
            System.out.println("资源被占用中...");
            Thread.sleep(1000); // 模拟操作
        } finally {
            semaphore.release(); // 释放许可证
        }
    }
}

import java.util.concurrent.CountDownLatch;
public class CountDownLatchExample {
    public static void main(String[] args) throws InterruptedException {
        CountDownLatch latch = new CountDownLatch(3); // 初始化计数器为3
        for (int i = 0; i < 3; i++) {
            new Thread(() -> {
                System.out.println("子线程完成任务");
                latch.countDown(); // 计数器减1
            }).start();
        }
        latch.await(); // 主线程等待计数器归零
        System.out.println("所有任务完成，主线程继续");
    }
}

import java.util.concurrent.CyclicBarrier;
public class CyclicBarrierExample {
    public static void main(String[] args) {
        CyclicBarrier barrier = new CyclicBarrier(3, () -> 
            System.out.println("所有线程到达屏障，执行后续任务"));
        for (int i = 0; i < 3; i++) {
            new Thread(() -> {
                try {
                    System.out.println("线程到达屏障");
                    barrier.await(); // 等待其他线程
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }
}