在多线程开发中，经常会出现一种情况，我们希望读写分离。就是对于读取这个动作来说，可以同时有多个线程同时去读取这个资源，但是对于写这个动作来说，只能同时有一个线程来操作，而且同时，当有一个写线程在操作这个资源的时候，其他的读线程是不能来操作这个资源的，这样就极大的发挥了多线程的特点，能很好的将多线程的能力发挥出来。
在Java中，ReadWriteLock这个接口就为我们实现了这个需求，通过他的实现类ReentrantReadWriteLock我们可以很简单的来实现刚才的效果，下面我们使用一个例子来说明这个类的用法。
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package com.bird.concursey.charpet3; import java.util.concurrent.locks.ReadWriteLock; import java.util.concurrent.locks.ReentrantReadWriteLock; public class PricesInfo { private double price1; private double price2; private ReadWriteLock lock; public PricesInfo() { price1 = 1.0; price2 = 2.0; lock = new ReentrantReadWriteLock(); } public double getPrice1() { //读取资源锁定 lock.readLock().lock(); double value = price1; lock.readLock().unlock(); return value; } public double getPrice2() { lock.readLock().lock(); double value = price2; lock.readLock().unlock(); return value; } public void setPrices(double price1, double price2) { lock.writeLock().lock(); this.price1 = price1; this.price2 = price2; lock.writeLock().unlock(); } } |
下面是读和写两个不同的类
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package com.bird.concursey.charpet3; public class Reader implements Runnable { private PricesInfo pricesInfo; public Reader(PricesInfo pricesInfo) { this.pricesInfo = pricesInfo; } @Override public void run() { for (int i = 0; i < 10; i++) { System.out.printf("%s: Price 1: %f\n", Thread.currentThread() .getName(), pricesInfo.getPrice1()); System.out.printf("%s: Price 2: %f\n", Thread.currentThread() .getName(), pricesInfo.getPrice2()); } } } |
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package com.bird.concursey.charpet3; public class Writer implements Runnable { private PricesInfo pricesInfo; public Writer(PricesInfo pricesInfo) { this.pricesInfo = pricesInfo; } @Override public void run() { for (int i = 0; i < 3; i++) { System.out.printf("Writer: Attempt to modify the prices.\n"); pricesInfo.setPrices(Math.random() * 10, Math.random( ) * 8); System.out.printf("Writer: Prices have been modified.\n"); try { Thread.sleep(2); } catch (InterruptedException e) { e.printStackTrace(); } } } public static void main(String[] args) { PricesInfo pricesInfo = new PricesInfo(); Reader readers[] = new Reader[5]; Thread threadsReader[] = new Thread[5]; for (int i = 0; i < 5; i++){ readers[i] = new Reader(pricesInfo); threadsReader[i] = new Thread(readers[i]); } Writer writer = new Writer(pricesInfo); Thread threadWriter = new Thread(writer); for (int i = 0; i < 5; i++){ threadsReader[i].start(); } threadWriter.start(); } } |
总结
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原文链接：http://blog.csdn.net/a352193394/article/details/39405287#comments
