1 package com.thread;2 3 import java.util.Random;4 import java.util.concurrent.locks.ReentrantReadWriteLock;5 6 public class ReadWriteLockTest {7     public static void main(String[] args) {8         final Queue3 q3 = new Queue3();9         for(int i=0;i<3;i++)
10         {
11             new Thread(){
12                 public void run(){
13                     while(true){
14                         q3.get();
15                     }
16                 }
17
18             }.start();
19         }
20         for(int i=0;i<3;i++)
21         {
22             new Thread(){
23                 public void run(){
24                     while(true){
25                         q3.put(new Random().nextInt(10000));
26                     }
27                 }
28
29             }.start();
30         }31     }
32 }
33
34 class Queue3{
35     private Object data = null;//共享数据，只能有一个线程能写该数据，但可以有多个线程同时读该数据。
36     private ReentrantReadWriteLock rwl = new ReentrantReadWriteLock();
37     public void get(){
38         rwl.readLock().lock();//上读锁，其他线程只能读不能写
39         System.out.println(Thread.currentThread().getName() + " be ready to read data!");
40         try {
41             Thread.sleep((long)(Math.random()*1000));
42         } catch (InterruptedException e) {
43             e.printStackTrace();
44         }
45         System.out.println(Thread.currentThread().getName() + "have read data :" + data);
46         rwl.readLock().unlock(); //释放读锁，最好放在finnaly里面
47     }
48
49     public void put(Object data){
50
51         rwl.writeLock().lock();//上写锁，不允许其他线程读也不允许写
52         System.out.println(Thread.currentThread().getName() + " be ready to write data!");
53         try {
54             Thread.sleep((long)(Math.random()*1000));
55         } catch (InterruptedException e) {
56             e.printStackTrace();
57         }
58         this.data = data;
59         System.out.println(Thread.currentThread().getName() + " have write data: " + data);
60
61         rwl.writeLock().unlock();//释放写锁
62     }
63 }

Thread-0 be ready to read data!
Thread-1 be ready to read data!
Thread-2 be ready to read data!
Thread-0have read data :null
Thread-2have read data :null
Thread-1have read data :null
Thread-5 be ready to write data!
Thread-5 have write data: 6934
Thread-5 be ready to write data!
Thread-5 have write data: 8987
Thread-5 be ready to write data!
Thread-5 have write data: 8496

 1 package com.thread;2 3 import java.util.HashMap;4 import java.util.Map;5 import java.util.concurrent.locks.ReadWriteLock;6 import java.util.concurrent.locks.ReentrantReadWriteLock;7 8 public class CacheDemo {9     private Map<String, Object> map = new HashMap<String, Object>();//缓存器
10     private ReadWriteLock rwl = new ReentrantReadWriteLock();
11     public static void main(String[] args) {
12
13     }
14     public Object get(String id){
15         Object value = null;
16         rwl.readLock().lock();//首先开启读锁，从缓存中去取
17         try{
18             value = map.get(id);
19             if(value == null){  //如果缓存中没有释放读锁，上写锁
20                 rwl.readLock().unlock();
21                 rwl.writeLock().lock();
22                 try{
23                     if(value == null){
24                         value = "aaa";  //此时可以去数据库中查找，这里简单的模拟一下
25                     }
26                 }finally{
27                     rwl.writeLock().unlock(); //释放写锁
28                 }
29                 rwl.readLock().lock(); //然后再上读锁
30             }
31         }finally{
32             rwl.readLock().unlock(); //最后释放读锁
33         }
34         return value;
35     }
36
37 }