Inheritance

Inheritance

mechanism for code reusability in object-oriented programming

Inheritance

relationship between related types/classes in a superclass–subclass hierarchy.

is-a, has-a

relationships in inheritance

Inheritance

Derived classes (subclasses) are created from base classes (superclasses).

Is-a relationship

Shape (superclass) → Circle, Rectangle (subclasses).

share attributes and behaviors

Objects in two or more classes may ___, but also have unique ones.

Substitution principle

Every circle is a shape. Every rectangle is a shape. Not every shape is a circle/rectangle.

public, protected

subclasses can inherit only features with these access modifier

Superclass constructor

superclasses may define constructors; subclasses can invoke them

Extends keyword

indicates that a subclass inherits from a superclass

Protected modifier

feature is accessible to:

• its own class,

• classes in the same package, and to

• subclasses (even outside the package)

Super keyword

used within a subclass to refer to its superclass; can invoke its constructor, call its method, or access superclass attribute

multiple inheritance, single inheritance

Kinds of Inheritance

Multiple inheritance

subclass derived from more than one superclass

EX. A child can come from two parents

• Complicated to implement; used in C++

Single inheritance

• Subclass derived from only one superclass

• Simple subtyping scheme

ultimate cosmic object class

all Java classes descend from this

Protected

Allows features to be inherited by subclasses even outside the same package.

subclass

Always call the superclass constructor in a ___

Method overriding

Subclass provides a specific implementation of a method from its superclass.

return type, method signature

In method overriding, ___ and ___ (name, parameter types) must be the same as the original method