HashMap Performance when overriding hashcode method

Question

In a HashMap, if I put custom objects as a key.

What would happen if I override hashCode() method and implement it to pass value as \'1

Answer 1

Always returning 1 in hashCode() will degrade the performance of HashMap. Every object defaults to the same bucket, and the hash tables become linked lists. According to Effective Java, item 9, you get quadratic time instead of linear.

Returning a random value will violate the provision that equal objects have equal hashCodes, you won't be able to retrieve the stored objects.