What will happen if, in a class used as a key, the equals and hashCode methods behave differently despite having matching values?

If in a class used as a key in collections like HashMap, the methods equals() and hashCode() are implemented inconsistently (i.e., two objects are considered equal by equals(), but have different hashCodes(), or vice versa), this will lead to incorrect behavior of the collection.

What exactly will happen:

• HashMap uses hashCode() to determine the bucket where the key is placed.
• If two equal objects have different hashCodes(), they will go into different buckets, and searching by key may not find the required element.
• This violates the contract that equal objects must have the same hashCode().

As a result:

• When trying to get a value by a key that is equal to an existing one but has a different hashCode(), the search will not find the element.
• Duplicate keys may occur, which will violate the application's logic.

Therefore, it is always important to override equals() and hashCode() consistently to ensure the correct operation of hash collections.