AtomicStampedReference 注意事项 2019-06-08

以下是AtomicStamedReference中compareAndSet方法的源码

public boolean compareAndSet(V expectedReference,
                                 V newReference,
                                 int expectedStamp,
                                 int newStamp) {
    Pair current = pair;
    return
           expectedReference == current.reference &&
            expectedStamp == current.stamp &&
            ((newReference == current.reference &&
              newStamp == current.stamp) ||
             casPair(current, Pair.of(newReference, newStamp)));
}

从上述源码可知reference与stamp比较时使用的是==而非equal方法。
因此expectedReference因直接传入getReference()方法的返回值。同时对原始数据类型的使用需特别注意。以下为错误示例：
❌

public class AtomicStampedTest {

    private static AtomicStampedReference atomicInteger = new AtomicStampedReference<>(0, 0);

    public static Integer incrAtomicInteger(AtomicStampedReference atomicInteger){
        while (true) {
            final int timeStamp = atomicInteger.getStamp();
            int /* ❌错误，应改为Integer*/ currunt = atomicInteger.getReference();
            Integer attemptValue = currunt + 1;
            int nextStamp = timeStamp + 1;
            if (atomicInteger.compareAndSet(currunt, attemptValue, timeStamp, nextStamp)) {
                return attemptValue;
            }
        }
    }

    public static void main(String[] args) {
        Integer value = incrAtomicInteger(atomicInteger);
        System.out.println(value);
    }
}