多线程的一些工具类

1. countdownlatch

public class Main {
    public static void main(String[] args) throws InterruptedException {
        // 主线程等待n个子线程，每次调用countdown表示该线程准备好了
        CountDownLatch latch = new CountDownLatch(2);
        new Thread(() -> {
            System.out.println("线程1执行");
            latch.countDown();
        }).start();
        new Thread(() -> {
            System.out.println("线程2执行");
            latch.countDown();
        }).start();
        new Thread(() -> {
            System.out.println("线程3执行");
            latch.countDown();
        }).start();
        latch.await();
        System.out.println("执行结束");
    }
}

2. cyclicbarrier

public class Main {
    public static void main(String[] args) throws InterruptedException {
        // 当n个线程同时到达时执行回调方法，await表示线程到达
        CyclicBarrier cyc = new CyclicBarrier(2, () -> {
            System.out.println("到齐啦");
        });
        new Thread(() -> {
            try {
                cyc.await();
                System.out.println("线程1运行");
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            } catch (BrokenBarrierException e) {
                throw new RuntimeException(e);
            }
        }).start();        
        new Thread(() -> {
            try {
                cyc.await();
                System.out.println("线程2运行");
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            } catch (BrokenBarrierException e) {
                throw new RuntimeException(e);
            }
        }).start();
    }
}

3. semaphore

public class Main {
    public static void main(String[] args) throws InterruptedException {
        // 控制最多n个线程同时执行,acquire表示获取信号量，release是释放
        Semaphore semaphore = new Semaphore(3);
        for (int i = 0; i < 10; i++) {
            int ii = i;
            new Thread(() -> {
                try {
                    semaphore.acquire();
                    System.out.println("线程" + ii + "运行");
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
            }).start();
        }
    }
}

4. atomicinteger

public class Main {
    public static volatile AtomicInteger INTEGER = new AtomicInteger(0);
    public static void main(String[] args) throws InterruptedException {
        // 原子类实现自增操作
        for (int i = 0; i < 10; i++) {
            new Thread(INTEGER::incrementAndGet).start();
        }
        Thread.sleep(5);
        System.out.println(INTEGER.get());
    }
}