使用runnable实现数据共享，供大家参考，具体内容如下
先上代码：
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public class testthread { private static final logger logger = loggerfactory.getlogger(testthread.class); private final class myrunnable implements runnable { private int i; public myrunnable() { this.i = 10; } public void run() { while(i > 0) { synchronized (this) { if (i > 0) { i--; logger.debug("{} buy one ticket, {} left. ", thread.currentthread().getname(), i); } } } } } @test public void testrunable() throws interruptedexception{ myrunnable myrunnable = new myrunnable(); thread th1 = new thread(myrunnable); thread th2 = new thread(myrunnable); th1.start(); th2.start(); th1.join(); th2.join(); }} |
楼上的代码很简单，模拟一个售票系统。通过两个thread对象开启两条线程同时运行一个myrunnable实例。
几个注意点：
1. 没有加上synchronised关键词的话，即
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public void run() { while(i > 0) { if (i > 0) { i--; logger.debug("{} buy one ticket, {} left. ", thread.currentthread().getname(), i); } } } |
系统的运行结果：
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thread-1 buy one ticket, 8 left. thread-2 buy one ticket, 8 left. thread-2 buy one ticket, 6 left. thread-1 buy one ticket, 6 left. thread-2 buy one ticket, 5 left. thread-1 buy one ticket, 4 left. thread-2 buy one ticket, 3 left. thread-1 buy one ticket, 2 left. thread-2 buy one ticket, 1 left. thread-1 buy one ticket, 0 left. |
可以看到，缺少同步的程序输出明显有问题。
2. 在进入同步代码块之后，还需要对i的值再进行一次判断，即，如果不加if判断：
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public void run() { while(i > 0) { synchronized (this) { i--; logger.debug("{} buy one ticket, {} left. ", thread.currentthread().getname(), i); } } } |
程序的运行结果为：
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thread-2 buy one ticket, 9 left. thread-2 buy one ticket, 8 left. thread-2 buy one ticket, 7 left. thread-2 buy one ticket, 6 left. thread-2 buy one ticket, 5 left. thread-2 buy one ticket, 4 left. thread-2 buy one ticket, 3 left. thread-2 buy one ticket, 2 left. thread-2 buy one ticket, 1 left. thread-2 buy one ticket, 0 left. thread-1 buy one ticket, -1 left. |
可以看出，出现了“多卖”的现象， 所以需要在进入同步代码块中再进行一次if判断。
总结
synchronised用于互斥访问共享变量， 并在同步代码块中使用if判断更新共享变量。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。
原文链接：https://blog.csdn.net/NewUser2771894007/article/details/79630721
