Java-5 - 新特性 - 锁

来源：互联网发布：淘宝刷心悦会员的原理编辑：程序博客网时间：2024/06/14 11:35

Java5 的 java.util.concurrent.locks 为锁和等待条件提供一个框架的接口和类，它不同于内置同步和监视器。更灵活地使用锁和条件。

java.util.concurrent.locks包的接口:

|-- Lock接口--------替代了synchronized 方法和语句的使用。为同步代码块和同步函数提供了更广泛的锁定操作，将同步的隐示锁操作变成实现操作、

|-- ReentrantLock类--------一个可重入的互斥锁Lock，它封装了隐示锁操作的方法，但功能更强大。(一个实现了Lock接口的类)

|-- lock()--------获取锁、

|-- unlock()------释放锁、

|-- Condition接口------替代了 Object 监视器方法的使用。对Object的监视器方法(wait、notify 和notifyAll)进行单独封装，变成监视器对象，可以和任意Lock 实现组合使用。

|-- await()------等待。throws InterruptedException、

|-- signal()-----唤醒一个等待线程。

|-- signalAll()---唤醒所有等待线程。

/*北京烤鸭制作和消费的实现至少要有两个线程：1.生产烤鸭的线程生产线程的任务,生产烤鸭。2.消费烤鸭的线程消费线程的任务，消费烤鸭。1线程和2线程是两个不同对象，有两种不同的run方法，但是他们都是在操作同一资源。都是对共享资源烤鸭的操作，为了避免出现线程安全问题，我们要使用同步。可以把共享资源和对共享资源的操作方法封装在缓冲区。代码实现：1.创建一个缓冲区,2.创建两个线程任务,3.创建线程，4.开启线程。*///简单烤鸭，生产一只，消费一只//引入包。。。import java.util.concurrent.locks.*;class KaoYaTest  {public static void main(String[] args) {//创建共享资源对象KaoYaBuffer kaoya = new KaoYaBuffer();//创建生产任务ShengChang sc = new ShengChang(kaoya);//创建消费任务XiaoFei xf = new XiaoFei(kaoya);Thread t1 = new Thread(sc,"张三");//张三线程Thread t2 = new Thread(sc,"李四");Thread t3 = new Thread(xf,"王五");Thread t4 = new Thread(xf,"赵六");t1.start();t2.start();t3.start();t4.start();}}//缓冲区class KaoYaBuffer{//创建一个互斥锁final Lock lock = new ReentrantLock();//创建生产监视器final Condition shengchang_condi  = lock.newCondition(); //创建消费监视器    final Condition xiaofei_condi = lock.newCondition(); //烤鸭的名字private String name;//烤鸭的编号private int count = 1;//标记private boolean flag = false;//对烤鸭的生产操作public void set(String str){//获取锁lock.lock();try{while(flag)//当有烤鸭时，生产等待try{shengchang_condi.await();}catch(InterruptedException e){}name = str + count;count++;System.out.println(Thread.currentThread().getName()+"生产"+name);flag = true;//把标记改成有烤鸭状态//唤醒消费线程xiaofei_condi.signal();}finally{//释放锁lock.unlock();}}//对烤鸭的消费操作public void get(){lock.lock();try{while(!flag)try{xiaofei_condi.await();}catch(InterruptedException e){}System.out.println(Thread.currentThread().getName()+"消费"+name);flag = false;shengchang_condi.signal();}finally{lock.unlock();}}}//生产线程任务class ShengChang implements Runnable{private KaoYaBuffer k;ShengChang(KaoYaBuffer k){this.k = k;}public void run(){while(true){k.set("北京烤鸭");}}}//消费线程任务class XiaoFei implements Runnable{private KaoYaBuffer k;XiaoFei(KaoYaBuffer k){this.k = k;}public void run(){while(true){k.get();}}}

/** 存钱取钱操作 **/

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 +                                '}';        }}

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