You should override equals() and hashCode() together to maintain the general contract between them. According to the contract:

  • If two objects are considered equal by equals(), they must have the same hash code.
  • If two objects have the same hash code, it does not necessarily mean they are equal, but they must be placed in the same bucket in hash-based collections (like HashMap, HashSet).

Failing to override both methods properly can cause incorrect behavior in collections, leading to bugs in your program, such as objects not being found in a HashMap or HashSet.