Method Overriding and Polymorphism

Inheritance allows classes to acquire fields and methods from a parent. However, inheritance isn’t just about copying code; it’s about specialization. Often, a subclass needs to inherit a general behavior but implement it differently. For example, a “Notification” system might know how to “send” a message, but an “Email” sends differently than an “SMS.”

In this lesson, we will learn how to customize inherited behavior and how to treat different objects as a single, unified type, a concept that makes Java applications flexible and scalable.

Redefining behavior with overriding

When a subclass inherits a method, it can provide its own specific implementation. This is called method overriding. Overriding allows a subclass to replace the behavior defined in its superclass while keeping the same method name and parameters.

To override a method, we define it in the subclass with the exact same signature (name and parameter list) as the parent. We also add the @Override annotation. While this annotation is optional, we always use it because it forces the compiler to verify that we are actually overriding a method. If we make a typo in the name or get the parameters wrong, the compiler will catch the error immediately. @Override also prevents accidental overloading, where a method with a similar name but different parameters is created instead of overriding the intended method.

Rules for overriding

1. Same signature: The method name and parameter list must match the parent’s method exactly. ... ...