Search code examples
javahashcode

Are two Java objects with same hashcodes not necessarily equal?

I understand why providing same hashcode for two equal (through equals) objects is important. But is the vice versa true as well, if two objects have same hashcode do they have to be equal? Does the contract still hold? I cannot find an example where this could happen, because if all those attributes that are taking part in equals method are being used to override hashcode method as well then we will always same hashcode of objects that are equal. Please comment.

Solution

  • If two objects have the same hashcode then they are NOT necessarily equal. Otherwise you will have discovered the perfect hash function.

    But the opposite is true: if the objects are equal, then they must have the same hashcode.