读写锁ReadWriteLock的基本使用，创建一个缓冲池。

创建一个读写锁

ReadWriteLock rw = new ReentrantReadWriteLock();

代码：

package Exce;


import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;


public class ThreadCacheTest {


/**读写锁的应用
* @param args
*/
private Map<String, Object> map = new HashMap<String, Object> ();
public static void main(String[] args) {
for(int i=1;i<=3;i++){
new Thread(new Runnable(){

@Override
public void run() {

System.out.println(Thread.currentThread().getName()+"取到数据--"+new ThreadCacheTest().getData("aa"));
}

}).start();

 try {
Thread.sleep(2000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} 
}
}
public Object getData(String key){
ReadWriteLock rw1 = new ReentrantReadWriteLock();
//上一个读锁
rw1.readLock().lock();
Object value = null;
try{
   value = map.get(key);
 //要上写锁，先释放读锁
rw1.readLock().unlock();
rw1.writeLock().lock();
try{
if(value == null){

value = "abc";
}
}finally{
rw1.writeLock().unlock();
}
rw1.readLock().lock();
}finally{ 
rw1.readLock().unlock();
}

return value;
}
}