In Java, what are the key restrictions and rules that apply when overriding a method in a subclass?

Introduction / Context:
Method overriding is a core concept in Java that enables runtime polymorphism. When interviewing Java developers, questions about overriding restrictions are used to check understanding of object oriented design and the Java language specification. If you do not know the rules, you can accidentally break polymorphism or introduce runtime errors.

Given Data / Assumptions:

• There is a superclass that defines an instance method.
• A subclass wants to provide its own implementation of that method.
• The subclass method is intended to override the superclass method, not simply overload it.
• Both methods have the same logical behavior, but the subclass may refine it.

Concept / Approach:
For a method to override another method in Java, certain conditions must be met. The method name and parameter list (the signature) must be exactly the same. The return type must be the same or a covariant (more specific) type. The access level of the overriding method cannot be more restrictive than that of the overridden method. Also, the overriding method cannot declare broader checked exceptions than the overridden method. Finally, static and final methods cannot be overridden; static methods are hidden, and final methods are completely non overridable.

Step-by-Step Solution:
1. Ensure that the subclass method has the same name and the same parameter list as the superclass method. 2. Choose a return type that is either identical to the superclass method or a subclass of that return type (covariant return type). 3. Set the access modifier so that it is at least as accessible as in the superclass, for example changing protected to public is allowed, but changing public to protected is not. 4. When declaring checked exceptions, do not add new broader checked exceptions; you may declare the same exceptions or a subset of them. 5. Verify that the superclass method is not final or static, because those cannot be truly overridden.

Verification / Alternative check:
Modern IDEs such as IntelliJ IDEA and Eclipse help verify overriding rules. When you add the @Override annotation to the subclass method, the compiler checks whether it truly overrides a method from a superclass or interface. If you break any rule, such as mismatched signature or illegal access change, you get a compile time error. This is a convenient way to confirm that your overriding is valid and intentional.

Why Other Options Are Wrong:
Option B is wrong because overriding methods do not have to be static or final; in fact, final methods cannot be overridden at all, and static methods use a different mechanism called method hiding. Option C describes overloading, where the parameter list is different. Option D is incorrect because Java does restrict access level and checked exceptions; you cannot make a public method protected in the subclass, and you cannot add broader checked exceptions to the throws clause when overriding.

Common Pitfalls:
Common mistakes include thinking that a method overrides another when it actually overloads it due to a slightly different parameter list, or accidentally decreasing the access level. Another pitfall is adding new checked exceptions that break existing client code. Developers also sometimes forget to add @Override, missing the chance to catch such errors early. Understanding and respecting these overriding rules leads to clearer, safer polymorphic behavior in Java applications.

Final Answer:
The overriding method must have the same signature, cannot reduce the access level, and cannot throw broader checked exceptions than the overridden method.