Java多线程--volatile

volatile不会提供加锁机制，只会保证修改对其他线程的可见性，当只有一个线程修改变量值，多个线程读取变量值时可以使用volatile，当多个线程修改变量值时，不能保证变量的安全，会发生丢失更新现象。

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class Test {
	volatile static int m = 0;

	public static void main(String[] args) throws InterruptedException {
		ExecutorService exec = Executors.newCachedThreadPool();
		for (int j = 0; j < 10; j++) {
			exec.execute(new Runnable() {
				int count = 1000;

				@Override
				public void run() {
					while (count-- > 0) 
							m++;
				}

			});
		}
		exec.shutdown();
		while (Thread.activeCount() > 1) {
			Thread.yield();
		}
		System.out.println(m);
	}
}