Java并发中 volatile Demo

class VolatileExample {
    volatile int x = 0;
     int b = 0;

     public void write() {
        x = 5;
        b = 1;
    }
   
    /**
     *  
     *   加上 volatile 栈中变量会无效，每次读取主存变量。
     *  不加volatile 每次读取的是栈中变量   
     */

    public void read() {
        //int dummy = b;
        while (x != 5) {
        }
    }

    public static void main(String[] args) throws Exception {
        final VolatileExample example = new VolatileExample();
        Thread thread1 = new Thread(new Runnable() {
            public void run() {
                example.write();
            }
        });
        Thread thread2 = new Thread(new Runnable() {
            public void run() {
                example.read();
            }
        });
        thread2.start();
        Thread.sleep(1000);
        thread1.start();
       
    }
}

http://ifeve.com/how-to-use-volatile/