If a class overrides the default implementation of equality defined by the Object.equals method, and a subclass of that class declares additional fields to the ones that it inherits, the results of equals may be wrong, unless that subclass also redefines equals.

See if the subclass should provide its own implementation of equals to take into account the additional fields that it declares.

If the subclass cannot provide its own implementation of equals because the inherited equals method is final, consider replacing inheritance by composition; instead of class B extending class A, class B could define a field of type A.

In the following example, rectangles r1 and r2 are calculated to be equal, even though they have different dimensions. This is because the class Rectangle does not override Square.equals, so it uses a test for equality that is only applicable to squares, not rectangles. (Note that, in practice, the example should also include an implementation of hashCode.)

To get the correct result, you must override Square.equals in class Rectangle.

Java API Specification: Object.equals().