ReentrantReadWriteLock类

读写锁表示有两个锁，一个是读操作相关的锁，称为共享锁；另一个写操作相关的锁，称为排它锁
多个线程可以同时进行读取操作，但同一时刻只允许一个线程进行写操作

读写实例

“读写”、“写读”、“写写”都是互斥的，而“读读”是异步的，非互斥的

class Service {

    private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();

    public void read() {
        try {
            try {
                lock.readLock().lock();
                System.out.println("read lock:"
                        + Thread.currentThread().getName() + "-"
                        + System.currentTimeMillis());
                Thread.sleep(10000);
            } finally {
                lock.readLock().unlock();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public void write() {
        try {
            try {
                lock.writeLock().lock();
                System.out.println("write lock:"
                        + Thread.currentThread().getName() + "-"
                        + System.currentTimeMillis());
                Thread.sleep(10000);
            } finally {
                lock.writeLock().unlock();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

class RService implements Runnable {

    private Service service;

    public RService(Service service) {
        this.service = service;
    }

    @Override
    public void run() {
        service.read();
    }
}

class WService implements Runnable {

    private Service service;

    public WService(Service service) {
        this.service = service;
    }

    @Override
    public void run() {
        service.write();
    }
}

public class Run {

    public static void main(String[] args) throws InterruptedException {
        Service service = new Service();
        Thread rThread = new Thread(new RService(service));
        rThread.start();
        Thread.sleep(1000);

        Thread wThread = new Thread(new WService(service));
        wThread.start();
    }
}