public class VolatileTest {    private volatile int i = 0;    public void add() {        i++;    }    public int getI() {        return this.i;    }    public static void main(String[] args) {        final VolatileTest volatileTest = new VolatileTest();        for (int i = 0; i < 10000; i++) {            new Thread(new Runnable() {                @Override                public void run() {                    try {                        Thread.sleep((int)Math.random() * 20);                    } catch (InterruptedException e) {                        e.printStackTrace();                    }                    volatileTest.add();                }            }).start();        }        System.out.println(volatileTest.getI());    }}

　　read-update-write并不是线程安全的