Method Overriding and Polymorphism - 11

Method Overriding

Key Concepts

• Method Overriding: Hiding of methods by subclasses.
• Inheritance: Extending class functionality and reusing code.
• Abstraction: Code written for a superclass works for its subclasses.
• Polymorphism: Achieved through method overriding, allowing a single method to work differently based on the subclass.
• Dynamic Dispatch: Java determines which method to call at runtime, irrespective of the variable type.

SuperGoose Example

• Goose subclasses Animal.
• The talk method in Goose hides the talk method in Animal.
• super.talk(): Calls the Animal version of talk from within Goose.

Animal Override Example

• Demonstrates dynamic dispatch: the instance's version of the method is always called.

Polymorphism

• Supports writing code that works with any subclass of a superclass.
• The interface remains consistent, but the implementation varies.

Expression Class

• Illustrates polymorphism using a simple arithmetic expression class.
• Includes integer literals, addition, and multiplication.
• Subclasses: Value, Add, Multiply.
• Employs inheritance, recursion, and method overriding.

Value Class

• Represents an integer literal value.

Add Class

• Represents the addition operator.
• Uses Expression to store any subclass.
• .describe() and .evaluate() methods are polymorphic and recursive.

Multiply Class

• Similar to the Add class, but represents multiplication.

\@Override Annotation

• Used to prevent errors in method overriding.
• Ensures the method signature (name and parameter list) is exactly the same as the superclass method.
• Provides the compiler with extra information to verify overriding.

Software Development Lifecycle (SDLC)

• An idealized, iterative view of software development.
• Design: Breaking problems into classes.
• Implementation: Writing those classes.
• Classes facilitate testing and maintenance through data hiding and abstraction.