Java多线程之并发锁

这是自JDK5.0开始提供的Java并发包里面的类

下面是关于Java并发锁的测试代码

package com.jadyer.thread.lock;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;/** * LockTest * @author 宏宇 * @create Mar 1, 2012 7:12:04 PM */public class LockTest {public static void main(String[] args) {FoodCenter fc = new FoodCenter();new Thread(new ThreadDog(fc, "It is dog`s food")).start();new Thread(new ThreadPig(fc, "It is pig`s food")).start();}}class ThreadDog implements Runnable{private FoodCenter fc;private String foodname;public ThreadDog(FoodCenter fc, String foodname){this.fc = fc;this.foodname = foodname;}@Overridepublic void run() {while(true){try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}fc.getFood(foodname);}}}class ThreadPig implements Runnable{private FoodCenter fc;private String foodname;public ThreadPig(FoodCenter fc, String foodname){this.fc = fc;this.foodname = foodname;}@Overridepublic void run() {while(true){try {Thread.sleep(2000);} catch (InterruptedException e) {e.printStackTrace();}fc.getFood(foodname);}}}/** * @see ========================================================================================= * @see java.util.concurrent是JDK5.0开始提供的Java并发包，其子包locks是专门用于处理线程锁的 * @see java.util.concurrent.locks.Lock较synchronized关键字比，有一个最大的区别，那就是 * @see Lock可以比synchronized更细粒度的控制锁，体现在try{...}finally{mylock.unlock();} * @see ========================================================================================= * @see Lock有点像公共厕所的门闩，只有正在使用厕所的人，把门闩打开出来了，其它人才可以使用公厕 * @see Lock比传统线程模型中的synchronized方式更加面向对象。与生活中的锁类似，锁本身也应该是一个对象 * @see 两个线程执行的代码片段要实现同步互斥的效果，那么这两个线程所使用的必须是同一个Lock对象 * @see 并且，锁应该位于待操作的资源类的内部方法中，而非线程代码中 * @see ========================================================================================= */class FoodCenter {Lock mylock = new ReentrantLock(); //创建一个锁public void getFood(String name) {int len = name.length();mylock.lock(); //上锁try {for (int i = 0; i < len; i++) {System.out.print(name.charAt(i));}System.out.println();} finally {mylock.unlock(); //解锁}}}

下面是关于Java读写锁的测试代码

package com.jadyer.thread.lock;import java.util.concurrent.locks.ReadWriteLock;import java.util.concurrent.locks.ReentrantReadWriteLock;/** * Java读写锁 * @see 锁分为读锁和写锁。多个读锁不互斥。读锁与写锁互斥。写锁与写锁互斥。这是由JVM自己控制的 * @see 如果代码只读数据，可以很多人同时读，但不能同时写，那就上读锁 * @see 如果代码修改数据，并且不允许同时读，只能一个人写，那就上写锁 * @see 总之：读的时候上读锁，写的时候上写锁 */public class ReadWriteLockDemo{private Object myData = 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ReadWriteLock rwl = new ReentrantReadWriteLock();public void get() {rwl.readLock().lock(); //读锁try {System.out.println(Thread.currentThread().getName() + " be ready to read data");Thread.sleep((long) (Math.random() * 1000));System.out.println(Thread.currentThread().getName() + " have read data : " + myData);} catch (InterruptedException e) {e.printStackTrace();} finally {rwl.readLock().unlock();}}public void put(Object data) {rwl.writeLock().lock(); //写锁try {System.out.println(Thread.currentThread().getName() + " be ready to write data");Thread.sleep((long) (Math.random() * 1000));this.myData = data;System.out.println(Thread.currentThread().getName() + " have write data : " + myData);} catch (InterruptedException e) {e.printStackTrace();} finally {rwl.writeLock().unlock();}}}