Setting own class as key in java Hashmap

Question

I have a class which I want to set up as keys in HashMap. I already have implemented the compareTo method for that class. But still when I do:

map.put(new MyKey(d         


        

Answer 1

You should implement equals() and hashCode(). Your class should also be immutable. If it is mutable, it's hash code can change after adding it to map. Then the map can have problems finding it.