COMP 155: Object Oriented Programming Concepts

Inheritance

Class obtains variables and methods from another class.

Subclass

Derived class that specializes behavior of superclass.

Superclass

Base class from which subclasses are derived.

Code Reuse

Using existing code to avoid duplication.

Class Hierarchy

Structure showing relationships between classes.

Transitive Inheritance

Subclass instances are also superclass instances.

extends keyword

Keyword used to inherit from another class.

Single Inheritance

One subclass extends one superclass.

Multi-level Inheritance

Subclass extends another subclass.

Hierarchical Inheritance

Multiple subclasses extend a single superclass.

Object Class

Default class at the top of hierarchy.

Method Overriding

Subclass provides its own implementation of superclass method.

Access Modifiers

Control visibility of class members (e.g., private).

Instance

Object created from a class.

Polymorphism

Ability to treat objects of different classes uniformly.

Encapsulation

Bundling data and methods that operate on data.

Abstract Class

Class that cannot be instantiated, may contain abstract methods.

Interface

Contract that classes can implement, defining methods.

Method Signature

Combination of method name and parameter types.

Constructor

Special method called when an object is instantiated.

Overloading

Defining multiple methods with the same name but different parameters.

Aggregation

Relationship where one class contains references to another.

Visibility Modifiers

Determine accessibility of class members.

Public Modifier

Accessible from outside the class definition.

Private Modifier

Accessible only within the class definition.

Protected Modifier

Accessible in subclasses and same package.

Default Access

Accessible within the current Java package.

Encapsulation

Restricting access to class members.

Super Keyword

Refers to superclass members in subclass.

Constructor Call

Invokes superclass constructor from subclass.

Method Call

Calls superclass method to avoid redundancy.

Variable Hiding

Subclass variables hide superclass variables.

Class A Example

Defines variable 'i' initialized to 1.

Class B Example

Defines variable 'i' initialized to 2.

Show Method

Prints value of variable 'i' in subclass.

Inheritance

Subclassing allows access to superclass members.

Access Control

Regulates member visibility in Java.

Protected vs Public

Protected is less accessible than public.

Protected vs Private

Protected is more accessible than private.

Method Redundancy

Avoids duplicate code by using superclass methods.

Class Member

Variables and methods within a class.

Java Package

Namespace for organizing related classes.

Super

Keyword to access superclass members.

Hiding

Subclass variable obscures superclass variable.

Multi-Level Hierarchy

Inheritance structure with multiple levels of classes.

Box Class

Represents a 3D box with dimensions.

BoxWeight Class

Extends Box to include weight property.

Ship Class

Extends BoxWeight to include shipping cost.

Volume Method

Calculates volume of a box: width height depth.

Constructor

Special method to initialize class objects.

Superclass

Class from which properties are inherited.

Subclass

Class that inherits properties from superclass.

Method Overriding

Subclass method replaces superclass method with same signature.

super Keyword

Used to call superclass constructors or methods.

Child Class

Class that inherits from a parent class.

Parent Class

Class from which child classes derive.

Reference Type

Type of variable that determines which class methods can be called.

Object Creation

Instantiating a class to create an object.

Encapsulation

Hiding class attributes and methods from outside access.

Constructor Overloading

Multiple constructors with different parameters in a class.

Inheritance

Mechanism to acquire properties from another class.

Data Member

Variable defined in a class.

Access Modifier

Defines visibility of class members (e.g., private, public).

Polymorphism

Ability to process objects differently based on their data type.

Overridden Method

Method in sub-class that replaces super-class method.

Sub-class Method

Method that overrides a super-class method.

Super-class Method

Original method hidden by sub-class method.

Hiding

Sub-class method conceals super-class method.

Overriding

Same method name in parent and child classes.

Method Signature

Method name and parameter types combined.

Polymorphism

Objects of different classes respond to same method.

Dynamic Binding

Method call resolved at runtime based on object type.

Polymorphic Reference

Reference that can point to different object types.

Overloading

Multiple methods with same name, different signatures.

Common Interface

Defined by super-class for sub-classes to implement.

Specialized Behavior

Sub-class implementation of inherited method.

Driver Class

Class containing main method to execute code.

Output of show()

Displays value of k from sub-class B.

Constructor

Method to initialize object attributes.

Inheritance

Mechanism where sub-class inherits properties of super-class.

Object Type

Class type of an instantiated object.

Method Invocation

Calling a method on an object.

Java Reference

Variable that holds the address of an object.

Polymorphic References

References resolved at run-time, not compile-time.

Dynamic Binding

Method invocation determined at run-time.

Dynamic Method Dispatch

Runtime selection of method based on object type.

Animal Class

Base class for animal sound methods.

Pig Class

Subclass of Animal that overrides animalSound.

Dog Class

Subclass of Animal that overrides animalSound.

makeSound() Method

Calls animalSound() based on Animal object.

Superclass Constructor

Called before subclass constructor executes.

Constructor Call Order

Superclass constructors execute before subclass constructors.

Implicit Constructor Call

Default constructor called if no explicit call is made.

Explicit Constructor Call

Use super() to call parameterized superclass constructor.

Base Class Object

All Java classes inherit from Object class.

Object Class Methods

Includes equals(), getClass(), hashCode(), toString().

instanceof Operator

Tests if an object is of a specific type.

Type Comparison Operator

Compares instance type with specified type.

Overriding Methods

Subclass provides specific implementation of superclass method.

Elegant Software Design

Achieved through careful use of polymorphic references.