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Tag: hashcode

How can UserDefined class be a key of hashmap if hashCode() & equals() return same value

I am trying to implement HashMap with UserDefined class as Key, i am successfull even when I implement both hashCode() (returns 0 for every object) & equals() (returns false for every object). My Code output:- Can anyone let me know the reason how it’s working Answer This is happening because equals is returning false. The equals/hashCode contract is completely broken.

How to create a HashMap with two keys (Key-Pair, Value)?

I have a 2D array of Integers. I want them to be put into a HashMap. But I want to access the elements from the HashMap based on Array Index. Something like: For A[2][5], map.get(2,5) which returns a value associated with that key. But how do I create a hashMap with a pair of keys? Or in general, multiple keys: