Object-Oriented Programming (OOP) Roadmap for System Design

Classes & Objects

Blueprints vs instances. Constructors, attributes, methods, and object lifecycle.

• →Constructor
• →Instance
• →State

Encapsulation

Hide internal state behind well-defined interfaces. Access modifiers: public, private, protected.

• →ACCESS CONTROL
• →GETTERS/SETTERS

Inheritance

Extend and reuse behavior. Single vs multiple inheritance. Method overriding. Super calls.

• →IS-A
• →EXTENDS
• →OVERRIDE

Polymorphism

Same interface, many implementations. Method overloading vs overriding. Runtime dispatch.

• →RUNTIME
• → OVERLOAD
• →DUCK TYPING

Abstraction

Expose only necessary complexity. Abstract classes vs interfaces. Contract-based design.

• →INTERFACE
• → ABSTRACT
• →CONTRACT