Question

Write a program that creates an abstract class called dimension. Create two subclasses, rectangle and triangle, that include appropriate methods for both the subclasses that calculate and display the area of the rectangle and triangle.

Short answer

Define an abstract class, implement subclasses Rectangle and Triangle with methods to calculate their areas.

Step-by-step solution

Define the Abstract Class

Create an abstract class named `Dimension` which serves as a blueprint for other shapes. This abstract class will include abstract methods that must be defined by any class inheriting from it. In many programming languages like Java, this can be achieved by including at least one abstract method (for example, `calculateArea()`). If using Python, use the `abc` module to define an abstract method.

Create the Rectangle Class

Define a class `Rectangle` that inherits from the `Dimension` abstract class. Implement the `calculateArea()` method which calculates the area of the rectangle using the formula \( \text{Area} = \text{length} \times \text{width} \). Add any required properties (e.g., constructor parameters to initialize length and width) and a method to display the calculated area.

Create the Triangle Class

Define a class `Triangle` inheriting from the `Dimension` abstract class. Implement the `calculateArea()` method specific to a triangle using the formula \( \text{Area} = \frac{1}{2} \times \text{base} \times \text{height} \). Include necessary properties (e.g., base and height initialization parameters) and include a method to display the area.

Implement and Test the Program

In your main program, create instances of `Rectangle` and `Triangle`, set their dimensions, and use the implemented methods to calculate and display their respective areas. This will confirm that the subclasses correctly implement the functionality defined in the abstract class.

Key concepts

Inheritance

Inheritance is a fundamental concept in object-oriented programming (OOP) that allows us to create a new class, known as a child class, that inherits properties and behaviors from an existing class, called the parent class. It is like reusing existing code to build new functionalities without rewriting it from scratch.
For example, in the exercise, the abstract class `Dimension` acts as the parent class. The Rectangle and Triangle, which are subclasses, inherit characteristics defined in `Dimension`. This means they must implement any abstract methods, such as `calculateArea()`, that are declared in the parent class.
Inheritance promotes a cleaner and more organized code structure by making it easy to add new features or modify existing ones. It also helps in reducing redundancy, as common properties and methods can be defined in the parent class and reused in child classes. Overall, it supports the concept of "DRY" - Don't Repeat Yourself, which is a key principle in programming.

Polymorphism

Polymorphism is a concept that allows methods to do different things based on which object they are acting on, even if the method calls are identical. It allows one interface to be used for a general class of actions. The specific action is determined by the exact nature or class of the object it is invoked upon.
In the provided exercise, polymorphism is seen in action through the method `calculateArea()` implemented in both `Rectangle` and `Triangle` subclasses. These subclasses provide their own specific implementation of the method, allowing each shape to calculate its area according to its own formula.
By using polymorphism, you can write flexible and reusable code. It enables programmers to invoke methods on objects without needing to know about their specific types at compile time. This leads to more dynamic and scalable programs. Moreover, polymorphism allows extensions and changes to be made with minimal impact on existing code bases, which is extremely valuable in maintaining large systems.

Object-Oriented Programming

Object-Oriented Programming (OOP) is a programming paradigm centered around objects rather than actions. It focuses on using objects to design and build applications. OOP principles ensure that software is modular, scalable, and easy to maintain by organizing code into units, each containing both data and functionality.
In OOP, everything is treated as an object, which encapsulates both data and methods that manipulate that data. This encapsulation helps protect the internal state of objects from being manipulated in unintended ways. The exercise shows OOP principles by defining classes such as `Dimension`, `Rectangle`, and `Triangle`. Each class is a blueprint for creating objects that belong to that class.
OOP leverages four main principles: encapsulation, inheritance, polymorphism, and abstraction. These allow for structuring programs in a way that reduces complexity and increases reusability. Through OOP practices, developers can build software that is more manageable and easier to debug, as real-world problems can be tackled in a more natural and realistic manner through the use of objects. As such, OOP continues to be a widely embraced methodology in software development.