对覆盖“ AbstractMap.SimpleEntry <>”中的“ equals（）”有什么意义吗？ “ equals（）”应该是最终的吗？

Question

Now, I am using guava collections, and am all good and happy. But, I want to understand why my own code did not work. I think I was trying to do the impossible:

I created a SortedSet<Map.Entry<K, V>> data structure. The bug was that I sometimes got duplicates in the Set. For me, a "duplicate" Map.Entry was one where its key matched another entry's key. I wanted to ignore the value with regard to calculating equality.

But, here is the API:
AbstractMap.SimpleEntry : public boolean equals(Object o)

I was like "No. I don't want that." I tried to bend SimpleEntry to my will by extending it and overriding equals() so as to only use the keys to decide equality.

question
Making AbstractMap.SimpleEntry only use the key to decide equality had some sort of ripple effect that would be almost impossible to fully understand?

Is there absolutely any possible reason to override equals() in AbstractMap.SimpleEntry? The javadoc is so restrictive with deciding equality, shouldn't equals() just be made final ?

Answer 1

It's conceivable that you might implement equals in some more optimized way, such as if you'd precached the hash code for the key. Otherwise, yes, it should be considered final. It is a part of the Map.Entry contract that equality must be tested on both key and the value.