What may you not do in a subclass?

In object-oriented programming, particularly in the context of subclasses, the ability to change aspects of inherited methods is subject to certain rules. A subclass can effectively inherit methods from a parent class and implement its own version of these methods, demonstrating polymorphism through method overriding. However, the signature of an inherited method must remain unchanged when it is overridden.

Modifying the signature – including the method name, return type, or parameter types – is not permissible. This is crucial because it breaks the contract established by the method in the parent class. Interfaces and polymorphism rely on consistent method signatures to function as expected in dynamic binding scenarios.

Adding new elements and constructors with their own signatures are permitted actions when defining subclasses, as these contribute to the specialization and extension of a class’s functionality. The ability to override inherited methods without altering the signature is an essential feature that allows subclasses to provide specific implementations while maintaining compatibility with the base class's interface.