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java并发编程是程序员基本技能。 我是李福春,我在准备面试,今天的题目是: synchronized和ReentrantLock的区别? 这两货都是java提供的同步机制,提供了互斥语义和可见性,当一个线程获得资源之后,其它竞争资源的线程必须等待或者堵塞。 区别如下:package org.example.mianshi.concurrent;/** * 线程不安全例子,共享数据sharedState * @author lifuchun */public class ThreadSafeSample { public int sharedState; public void nonSafeAction() { while (sharedState < 100000) { int former = sharedState++; int latter = sharedState; if (former != latter - 1) { System.out.printf("Observed data race, former is " + former + ", " + "latter is " + latter); } } } public static void main(String[] args) throws InterruptedException { final ThreadSafeSample sample = new ThreadSafeSample(); Thread threadA = new Thread() { @Override public void run() { sample.nonSafeAction(); } }; Thread threadB = new Thread() { @Override public void run() { sample.nonSafeAction(); } }; threadA.start(); threadB.start(); threadA.join(); threadB.join(); }}共享了数据,然后只有两个线程修改,就表现出数据的不一致性。 然后可以改造一下,分别使用sychronized ,ReetrantLock改造,保证线程安全。
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