Java中读写锁有个接口java.util.concurrent.locks.ReadWriteLock，也有具体的实现ReentrantReadWriteLock，详细的API可以查看JavaAPI文档。
下面这个例子是在文例子的基础上，将普通锁改为读写锁，并添加账户余额查询的功能，代码如下：
import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.locks.ReadWriteLock;import java.util.concurrent.locks.ReentrantReadWriteLock;/*** Java线程：锁** @author leizhimin 2009-11-5 10:57:29*/public class Test { public static void main(String[] args) { //创建并发访问的账户 MyCount myCount = new MyCount("95599200901215522", 10000); //创建一个锁对象 ReadWriteLock lock = new ReentrantReadWriteLock(false); //创建一个线程池 ExecutorService pool = Executors.newFixedThreadPool(2); //创建一些并发访问用户，一个信用卡，存的存，取的取，好热闹啊 User u1 = new User("张三", myCount, -4000, lock, false); User u2 = new User("张三他爹", myCount, 6000, lock, false); User u3 = new User("张三他弟", myCount, -8000, lock, false); User u4 = new User("张三", myCount, 800, lock, false); User u5 = new User("张三他爹", myCount, 0, lock, true); //在线程池中执行各个用户的操作 pool.execute(u1); pool.execute(u2); pool.execute(u3); pool.execute(u4); pool.execute(u5); //关闭线程池 pool.shutdown(); }}/*** 信用卡的用户*/class User implements Runnable { private String name; //用户名 private MyCount myCount; //所要操作的账户 private int iocash; //操作的金额，当然有正负之分了 private ReadWriteLock myLock; //执行操作所需的锁对象 private boolean ischeck; //是否查询 User(String name, MyCount myCount, int iocash, ReadWriteLock myLock, boolean ischeck) { this.name = name; this.myCount = myCount; this.iocash = iocash; this.myLock = myLock; this.ischeck = ischeck; } public void run() { if (ischeck) { //获取读锁 myLock.readLock().lock(); System.out.println("读：" + name + "正在查询" + myCount + "账户，当前金额为" + myCount.getCash()); //释放读锁 myLock.readLock().unlock(); } else { //获取写锁 myLock.writeLock().lock(); //执行现金业务 System.out.println("写：" + name + "正在操作" + myCount + "账户，金额为" + iocash + "，当前金额为" + myCount.getCash()); myCount.setCash(myCount.getCash() + iocash); System.out.println("写：" + name + "操作" + myCount + "账户成功，金额为" + iocash + "，当前金额为" + myCount.getCash()); //释放写锁 myLock.writeLock().unlock(); } }}/*** 信用卡账户，可随意透支 */class MyCount { private String oid; //账号 private int cash; //账户余额 MyCount(String oid, int cash) { this.oid = oid; this.cash = cash; } public String getOid() { return oid; } public void setOid(String oid) { this.oid = oid; } public int getCash() { return cash; } public void setCash(int cash) { this.cash = cash; } @Override public String toString() { return "MyCount{" + "oid='" + oid + '/'' + ", cash=" + cash + '}'; }}
写：张三正在操作MyCount{oid='95599200901215522', cash=10000}账户，金额为-4000，当前金额为10000写：张三操作MyCount{oid='95599200901215522', cash=6000}账户成功，金额为-4000，当前金额为6000写：张三他弟正在操作MyCount{oid='95599200901215522', cash=6000}账户，金额为-8000，当前金额为6000写：张三他弟操作MyCount{oid='95599200901215522', cash=-2000}账户成功，金额为-8000，当前金额为-2000写：张三正在操作MyCount{oid='95599200901215522', cash=-2000}账户，金额为800，当前金额为-2000写：张三操作MyCount{oid='95599200901215522', cash=-1200}账户成功，金额为800，当前金额为-1200读：张三他爹正在查询MyCount{oid='95599200901215522', cash=-1200}账户，当前金额为-1200写：张三他爹正在操作MyCount{oid='95599200901215522', cash=-1200}账户，金额为6000，当前金额为-1200写：张三他爹操作MyCount{oid='95599200901215522', cash=4800}账户成功，金额为6000，当前金额为4800Process finished with exit code 0
在实际开发中，最好在能用读写锁的情况下使用读写锁，而不要用普通锁，以求更好的性能。
此出处：http://lavasoft.blog.51cto.com/62575/222433
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