HashMap with double as key

Question

I found this post on stackoverflow that Double in HashMap states:

I was thinking of using a Double as the key to a HashMap but I know floating point comparisons are unsafe

But I can't really find out why it is unsafe to use doubles as key in your hashmap. Could you guys explain that to me?

What do you want to know that isn't already explained by the many answers to the existing question? — Oliver Charlesworth, Nov 22 '14 at 18:53
They are't "unsafe". It may lead to unexpected results if your expectation is incorrect, which it is likely to be. — harold, Nov 22 '14 at 18:57

score 1 · Answer 1 · answered Nov 22 '14 at 18:57

1

in simple words the key you are using for map, will be changed very much for even a small decimal change in fractions, the probability of missing the values is much higher.

hashCode of java.lang.Double says (int)(v^(v>>>32))

answered Nov 22 '14 at 18:57

prsutar

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HashMap with double as key

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