ReadWriteLock多线程下操作

ReadWriteLock是实现多线程环境下同步的一种方式。与synchronized相比，它在读的频率大于写的频率的时候，效率有很大的提升。而且拥有writelock的情况下还可以拥有readlock，相反则不能。

提供一个多线程环境的资源类
package zl.readandwrite.date;


import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

public class DateUtil {

private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
private Lock readLock = readWriteLock.readLock();
private Lock writeLock = readWriteLock.writeLock();
private String date = "2012-10-10" ;

public  String get() {
String date = null ;
readLock.lock();
try {
System.out.println(Thread.currentThread().getName());
Thread.sleep(2000);
System.out.println(Thread.currentThread().getName());
date = this.date ;
return date ;
} catch (InterruptedException e) {
// TODO 自动生成 catch 块
e.printStackTrace();
} finally {
readLock.unlock();
}
return null ;
}

public void set(String date) {
writeLock.lock() ;
try {
System.out.println(Thread.currentThread().getName());
Thread.sleep(2000);
System.out.println(Thread.currentThread().getName());
this.date = date ;
} catch (InterruptedException e) {
// TODO 自动生成 catch 块
e.printStackTrace();
} finally {
writeLock.unlock();
}
}

}


提供一个线程类：
package zl.readandwrite.thread;

import zl.readandwrite.date.DateUtil;

public class DateThread extends Thread {

private boolean flag ;
private DateUtil dateUtil ;

public DateThread(boolean flag , DateUtil dateUtil) {
this.flag = flag ;
this.dateUtil = dateUtil ;
}

public void run() {
if(flag)
dateUtil.get();
else
dateUtil.set("2011-11-11");
}
}

测试代码：
import zl.readandwrite.date.DateUtil;
import zl.readandwrite.thread.DateThread;


public class Test {

/**
* @param args
*/
public static void main(String[] args) {
DateUtil dateUtil = new DateUtil() ;
Thread date1 = new DateThread(true , dateUtil );
Thread date2 = new DateThread(false , dateUtil );

date1.setName("读数据1");
date2.setName("写数据2");


date2.start();
date1.start();

}

}


输出：
写数据2
写数据2
读数据1
读数据1