使用runnable实现 数据共享 ，供大家参考，具体内容如下
先上代码：
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 |
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
|
1 2 3 4 5 6 7 8 |
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：
|
1 2 3 4 5 6 7 8 9 10 |
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：
|
1 2 3 4 5 6 7 8 9 |
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：
|
1 2 3 4 5 6 7 8 9 10 11 |
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。
原文链接：https://blog.csdn.net/NewUser2771894007/article/details/79630721
查看更多关于使用Runnable实现数据共享的详细内容...