Question

Draw a class inheritance diagram for the following set of classes. • Class Goat extends Object and adds a member variable tail and functions milk and jump. • Class Pig extends Object and adds a member variable nose and functions eat and wallow. • Class Horse extends Object and adds member variables height and color, and functions run and jump. • Class Racer extends Horse and adds a function race. • Class Equestrian extends Horse and adds a member variable weight and functions trot and isTrained.

Short answer

Object -> Goat, Pig, Horse. Horse -> Racer, Equestrian.

Step-by-step solution

Identify the Base Class

Determine the base class from which all other classes are derived. In this case, the base class is `Object`.

Analyze Classes Directly Derived from Base Class

Identify the classes that extend from the `Object` class. Here, `Goat`, `Pig`, and `Horse` extend `Object`.

List Members of Each Class

For each class directly extending the base class, list their member variables and functions:- `Goat`: tail, milk(), jump()- `Pig`: nose, eat(), wallow()- `Horse`: height, color, run(), jump()

Analyze Subclasses of Horse

Identify classes that extend from `Horse`. Here, `Racer` and `Equestrian` are subclasses of `Horse`.

List Members of Subclasses of Horse

Detail the member variables and functions of the subclasses:- `Racer` (extends `Horse`): race()- `Equestrian` (extends `Horse`): weight, trot(), isTrained()

Draw the Class Inheritance Diagram

Draw the inheritance diagram as follows:1. `Object`2. From `Object`, draw lines to `Goat`, `Pig`, and `Horse`.3. From `Horse`, draw lines to `Racer` and `Equestrian`.

Key concepts

Class Hierarchy

A class hierarchy is essentially a structured tree of classes in object-oriented programming (OOP). Each node represents a class, and the edges represent inheritance relationships between those classes. In a hierarchical diagram, we can easily visualize how classes derive or extend from one another.
In the given exercise, the base or root class is `Object`. Every other class extends from `Object` directly or indirectly. Here's the breakdown:

• `Goat`, `Pig`, and `Horse` are directly derived from `Object`.
• `Racer` and `Equestrian` are derived from `Horse`, which means they indirectly extend `Object` via `Horse`.

Understanding the hierarchy helps clarify class relationships and can expose how features and functions are inherited and shared among classes.
Each level of the class hierarchy adds specificity. For example, a `Horse` includes properties like height and color, while its subclasses like `Racer` and `Equestrian` inherit these properties and add unique ones like race() for `Racer`.
This ensure that more specific classes do not have to rewrite code from more general classes, leading to more maintainable and readable code.

Object-Oriented Programming

Object-oriented programming (OOP) is a programming paradigm based on the concept of objects, which can contain both data (attributes or fields) and functions (methods). The main aim of OOP is to increase the flexibility and maintainability of code.
Key principles of OOP include:

• Encapsulation: Bundling the data and methods that operate on the data into a single unit or class.
• Abstraction: Hiding complex implementation details and showing only the essential features of the object.
• Polymorphism: Allowing objects to be treated as instances of their parent class rather than their actual class.
• Inheritance: Allowing a new class to inherit the properties and methods of an existing class.

In the exercise given, OOP concepts are applied where classes like `Goat`, `Pig`, and `Horse` are encapsulated units extending `Object`. Each class not only contains unique data and methods but also inherits general characteristics from their parent `
class.

Inheritance

Inheritance is one of the four major pillars of object-oriented programming. It allows a class (subclass) to inherit members (attributes and methods) from another class (superclass). Effective use of inheritance helps in code reuse, reduces redundancy, and improves software maintainability.
In the given example:

• `Goat`, `Pig`, and `Horse` are subclasses of `Object`.
• `Racer` and `Equestrian` are further subclasses of `Horse`.

All these subclasses inherit common features from their parent class `Object`, which means they all share some foundational characteristics. However, each subclass can add its features and modify inherited ones.
For example, `Horse` has attributes like height and color, and methods like run and jump. The subclasses `Racer` and `Equestrian` inherit these attributes and methods and augment them with specific features like race() for `Racer` and isTrained() for `Equestrian`.
Inheritance facilitates polymorphism: a `Racer` is a `Horse`, but a more specialized `Horse` with race capabilities. This makes the program dynamic and expandable without altering existing code<.