一、分为两种：公平和非公平 线程 a b c d e 公平：按顺序执行：a,b,d,e 读锁 c 写锁       1.a,b 执行 c 堵塞，d,e 等待       2.a,b执行结束 c获取锁 d,e堵塞等待       3.c执行结束 d开始执行，然后在唤醒e 非公平：       1，2步骤相同       3，c执行结束的时候，新来个线程 f读锁，在d没有唤醒的情况下，会获取读锁，然后在唤醒d，e

package 第三章.读写锁; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.locks.ReentrantReadWriteLock; /**  * Created by zzq on 2018/1/23.  */ public class WebTestReadAndWriteLock {
      ReentrantReadWriteLock lock = new ReentrantReadWriteLock();     public static void main(String[] args) {
          final WebTestReadAndWriteLock lock = new WebTestReadAndWriteLock();         // 建N个线程，同时读         ExecutorService service = Executors.newCachedThreadPool();         service.execute(new Runnable() {
              public void run() {
                  lock.readFile(Thread.currentThread());             }         });         service.execute(new Runnable() {
              public void run() {
                  lock.readFile(Thread.currentThread());             }         });         // 建N个线程，同时写         ExecutorService service1 = Executors.newCachedThreadPool();         service1.execute(new Runnable() {
              public void run() {
                  lock.writeFile(Thread.currentThread());             }         });         service.execute(new Runnable() {
              public void run() {
                  lock.readFile(Thread.currentThread());             }         });         service.execute(new Runnable() {
              public void run() {
                  lock.readFile(Thread.currentThread());             }         });         service1.execute(new Runnable() {
              public void run() {
                  lock.writeFile(Thread.currentThread());             }         });     }     // 读操作     public void readFile(Thread thread){
          lock.readLock().lock();         boolean readLock = lock.isWriteLocked();         if(!readLock){
              System.out.println("当前为读锁！");         }         try{
              for(int i=0; i<5; i++){
                  try {
                      Thread.sleep(1000);                 } catch (InterruptedException e) {
                      e.printStackTrace();                 }                 System.out.println(thread.getName() + ":正在进行读操作……");             }             System.out.println(thread.getName() + ":读操作完毕！");         }finally{
              System.out.println("释放读锁！");             lock.readLock().unlock();         }     }     // 写操作     public void writeFile(Thread thread){
          lock.writeLock().lock();         boolean writeLock = lock.isWriteLocked();         if(writeLock){
              System.out.println("当前为写锁！");         }         try{
              for(int i=0; i<5; i++){
                  try {
                      Thread.sleep(1000);                 } catch (InterruptedException e) {
                      e.printStackTrace();                 }                 System.out.println(thread.getName() + ":正在进行写操作……");             }             System.out.println(thread.getName() + ":写操作完毕！");         }finally{
              System.out.println("释放写锁！");             lock.writeLock().unlock();         }     } }