Inheritance: every key term you need

Inheritance

Subclass extends superclass; inherits fields/methods. Code reuse, hierarchy. class Dog extends Animal { }

Superclass vs Subclass

Superclass (parent): general class (Animal). Subclass (child): specific class (Dog). Subclass IS-A superclass.

Method Overriding

Subclass redefines superclass method. Same name/signature, different implementation. Enables polymorphism.

Method Overloading

Same method name, different parameter types/number. Different from overriding; both can coexist.

super Keyword

Access superclass methods/constructors. super.method() calls parent's method. super() calls parent's constructor.

Constructors & Inheritance

Subclass constructor must call super() to initialize superclass fields. super() must be first statement.

Access Modifiers & Inheritance

private: subclass can't access. protected: subclass can access. public: all can access. default: package only.

Abstract Classes

abstract class: can't instantiate directly. Forces subclasses to implement abstract methods. abstract method has no body.

Abstract Methods

Method with no implementation in superclass; subclass must override. Ensures all subclasses implement required behavior.

Polymorphism

One interface, many forms. Animal a = new Dog(); a.sound(); calls Dog's method, not Animal's. Dynamic dispatch.

Object Class

All classes extend Object implicitly. Methods: toString(), equals(), getClass(). Can override toString() for meaningful output.

Unit 9 Summary

Inheritance creates class hierarchy. Subclass extends superclass, overrides methods. Polymorphism via interfaces/abstract classes.

More AP Computer Science A guides

• Primitives
• Using Objects
• Boolean Expressions
• Loops
• Writing Classes