Why did java designers impose a mandate that
if obj1.equals(obj2) then
obj1.hashCode() MUST Be == obj2.hashCode()
Why did java designers impose a mandate that if obj1.equals(obj2) then obj1.hashCode() MUST Be
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Why did java designers impose a mandate that
if obj1.equals(obj2) then
obj1.hashCode() MUST Be == obj2.hashCode()
As far as I know that’s not baked into the language – you could technically have objects whose equals() method does not check the hashcode but you’ll get pretty peculiar results.
In particular if you put a bunch of these objects into a HashMap or HashSet the map/set will use the hashCode() method to determine whether the objects may be duplicates – so you can have a situation where a collection will store 2 objects you’ve defined as equals (which should never happen) because they’re each returning different hashCodes.