How can I have a HashMap with unique keys in java?

Question

How can I have a HashMap with unique keys in Java? Or even does this make any sense to have unique keys in HashMap or the keys are unique by default? I am a newbie. thx

Answer 1

HashMap is a collection to store (key,value) pairs and According to the documentation of HashMap the keys are always unique.

If you add a key which already exists(collision) in the hashmap, the old value will be replaced.