AtomicMarkableReference 可以解决ABA问题 #1627
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因为AtomicMarkableReference是通过内部类Pair实现数据存储，每次替换都是通过Pair.of方法new一个类出来进行替换原先的值
如果ABA出现，那么最后的A肯定是一个新的Pair实例，即当前的A和之前的A不是同一个实例，当现场使用compareAndSet则会返回false
以下是compareAndSet的实现：
Pair<V> current = pair;
return
expectedReference == current.reference &&
expectedMark == current.mark &&
((newReference == current.reference &&
newMark == current.mark) ||
casPair(current, Pair.of(newReference, newMark)));
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因为AtomicMarkableReference是通过内部类Pair实现数据存储，每次替换都是通过Pair.of方法new一个类出来进行替换原先的值
如果ABA出现，那么最后的A肯定是一个新的Pair实例，即当前的A和之前的A不是同一个实例，当线程使用compareAndSet则会返回false
以下是compareAndSet的实现：
public boolean compareAndSet(V expectedReference,
V newReference,
boolean expectedMark,
boolean newMark) {
Pair current = pair;
return
expectedReference == current.reference &&
expectedMark == current.mark &&
((newReference == current.reference &&
newMark == current.mark) ||
casPair(current, Pair.of(newReference, newMark)));
}