读写锁分为读锁和写锁，多个线程获取读锁不互斥，读写锁、写写锁互斥。

package readwrite;

import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * Created by lenovo on 2018/5/3.
 */
public class Service {

    private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();

    public void read() {
        try {
            lock.readLock().lock();
            System.out.println(Thread.currentThread().getName() + "获得读锁:" + System.currentTimeMillis());
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.readLock().unlock();
        }

    }

    public void write() {
        try {
            lock.writeLock().lock();
            System.out.println(Thread.currentThread().getName() + "获得写锁:" + System.currentTimeMillis());
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.writeLock().unlock();
        }
    }
}
package readwrite;

/**
 * Created by lenovo on 2018/5/3.
 */
public class Run {
    public static void main(String[] args) {
        Service service = new Service();
        Runnable readRunnable = new Runnable() {
            @Override
            public void run() {
                service.read();
            }
        };
        Runnable writeRunnable = new Runnable() {
            @Override
            public void run() {
                service.write();
            }
        };
        Thread readThread1 = new Thread(readRunnable);
        Thread readThread2 = new Thread(readRunnable);
        Thread writeThread = new Thread(writeRunnable);

        readThread1.start();
        readThread2.start();
        writeThread.start();

    }
}

输出

Thread-0获得读锁:1526039192299
Thread-1获得读锁:1526039192300
Thread-2获得写锁:1526039195300