ReentrantReadWriteLock分为读和写锁：
读与读锁不阻塞；
读与写锁阻塞;
写与写锁阻塞;
package com.lxht.test;

import java.util.concurrent.locks.ReentrantReadWriteLock;


/**
 * 测试ReentrantReadWriteLock
 */
public class TestReenTrantWriteReadLock {
    public static void main(String[] args) {
        ReentrantReadWriteLock readLock = new ReentrantReadWriteLock();
        WriteThread thread1 = new WriteThread(readLock);
        WriteThread thread4 = new WriteThread(readLock);
        Thread thread2 = new ReadThread(readLock);
        Thread thread3 = new ReadThread(readLock);
        thread1.start();
        thread2.start();
        thread3.start();
        thread4.start();
    }
}

/**
 * 读线程
 */
class ReadThread extends  Thread {
    private ReentrantReadWriteLock readLock;

    public ReadThread(ReentrantReadWriteLock readLock) {
        this.readLock = readLock;
    }

    public void run() {
        readLock.readLock().lock();
        for (int i = 0; i < 10; i++) {
            System.out.println(this.getName() + ";i =" + i);
        }
        readLock.readLock().unlock();
    }
}

/**
 * 写线程
 */
class WriteThread extends  Thread {
    private ReentrantReadWriteLock readLock;

    public WriteThread(ReentrantReadWriteLock readLock) {
        this.readLock = readLock;
    }

    public void run() {
        readLock.writeLock().lock();
        for (int i = 0; i < 10; i++) {
            System.out.println(this.getName() + ";i =" + i);
        }
        readLock.writeLock().unlock();
    }
}