Key existence check in HashMap

Question

Is checking for key existence in HashMap always necessary?

I have a HashMap with say a 1000 entries and I am looking at improving the efficiency. If the HashMap is b

Answer 1

1. If key class is your's make sure the hashCode() and equals() methods implemented.
2. Basically the access to HashMap should be O(1) but with wrong hashCode method implementation it's become O(n), because value with same hash key will stored as Linked list.