使用Runnable实现数据共享，供大家参考，具体内容如下

先上代码：

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

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：

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：

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：

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。