cas 代码

public class CounterUnsafe {
    volatile int i = 0;

    private static Unsafe unsafe = null;

    //i字段的偏移量
    private static long valueOffset;

    static {
        //unsafe = Unsafe.getUnsafe();
        try {
            Field field = Unsafe.class.getDeclaredField("theUnsafe");
            field.setAccessible(true);
            unsafe = (Unsafe) field.get(null);

            Field fieldi = CounterUnsafe.class.getDeclaredField("i");
            valueOffset = unsafe.objectFieldOffset(fieldi);

        } catch (NoSuchFieldException | IllegalAccessException e) {
            e.printStackTrace();
        }
    }


    public void add() {
        //i++;
        for (;;){
            int current = unsafe.getIntVolatile(this, valueOffset);
            if (unsafe.compareAndSwapInt(this, valueOffset, current, current+1))
                break;
        }
    }
}

public class Demo1_CounterTest {

    public static void main(String[] args) throws InterruptedException {
        final CounterUnsafe ct = new CounterUnsafe();

        for (int i = 0; i < 6; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    for (int j = 0; j < 10000; j++) {
                        ct.add();
                    }
                    System.out.println("done...");
                }
            }).start();
        }

        Thread.sleep(6000L);
        System.out.println(ct.i);
    }
}

标签：valueOffset,cas,代码,CounterUnsafe,unsafe,int,static,public
来源： https://www.cnblogs.com/wscp/p/16101830.html