CAS之基本类型与引用类型

1.1 long

1static final Unsafe unsafe ;
2static Long offset;
3private volatile long  state= 1;
4
5static {
6	try {
7		Field field = Unsafe.class.getDeclaredField("theUnsafe");
8		field.setAccessible(true);
9		unsafe = (Unsafe)field.get(null);	
10		offset = unsafe.objectFieldOffset(TestUnsafe.class.getDeclaredField("state"));
11	} catch (Exception e) {
12		System.out.println(e.getLocalizedMessage());
13		throw new Error(e);
14	}
15}
16
17public static void main(String[] args) {
18	TestUnsafe testUnsafe = new TestUnsafe();
19	boolean success = unsafe.compareAndSwapLong(testUnsafe,offset,1,3);
20	System.out.println("sucess:"+success+" after cas:"+testUnsafe.state);
21}
22
23

1.2 Long

1static final Unsafe unsafe ;
2static Long offset;
3//等同于Long.valueOf(1L)==>new Long(1L),是引用类型
4private volatile Long  state= 1L;
5
6static {
7​	try {
8​		Field field = Unsafe.class.getDeclaredField("theUnsafe");
9​		field.setAccessible(true);
10​		unsafe = (Unsafe)field.get(null);	
11​		offset = unsafe.objectFieldOffset(TestUnsafe2.class.getDeclaredField("state"));
12​	} catch (Exception e) {
13​		System.out.println(e.getLocalizedMessage());
14​		throw new Error(e);
15​	}
16}
17public static void main(String[] args) {
18​	TestUnsafe2 testUnsafe = new TestUnsafe2();
19​	boolean success = unsafe.compareAndSwapObject(testUnsafe,offset,1L,3L);
20​    //此处若换成 boolean success = unsafe.compareAndSwapLong(testUnsafe,offset,1L,3L);将失败,因为state是引用类型,不能用直接实际的值来比较,而应该用引用的实际内存地址做对比
21​	System.out.println("sucess:"+success+" after cas:"+testUnsafe.state);
22}
23
24​