UNIVERSITY OF WEST ATTICA
SCHOOL OF ENGINEERING
DEPARTMENT OF COMPUTER ENGINEERING AND INFORMATICS

University of West Attica · Department of Computer Engineering and Informatics

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Software Development Methodologies

Classes and Inheritance

Vasileios Evangelos Athanasiou
Student ID: 19390005

GitHub · LinkedIn

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Supervision

Supervisor: Georgios Prezerakos, Professor

UNIWA Profile · LinkedIn

Co-supervisor: Angelos Georgoulas, Assistant Professor

Scholar · LinkedIn

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Athens, March 2023

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README

Classes and Inheritance

This project implements Exercise 1: Classes and Objects, based on the specifications from the Department of Computer Engineering and Information Technology at the University of West Attica.

The goal is to design a Java class hierarchy that models different types of vehicles while practicing key Object-Oriented Programming (OOP) concepts.

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Table of Contents

Section	Folder/File	Description
1	INSTALL.md	Installation and execution instructions
2	README.md	Project overview and usage information
3	assign/	Assignment description documents
3.1	assign/SDM Exercise 1 (Classes & Inheritance).pdf	Assignment description (English)
3.2	assign/ΜΑΕ Ασκήση 1 (Classes & Inheritance).pdf	Assignment description (Greek)
4	src/	Java source code implementing classes and inheritance
4.1	src/Vehicle.java	Base Vehicle class definition
4.2	src/Car.java	Car class inheriting from Vehicle
4.3	src/Plane.java	Plane class inheriting from Vehicle
4.4	src/VehicleTest.java	Test program demonstrating the functionality of the classes

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1. Project Overview

The exercise demonstrates how to build a structured class hierarchy using:

• Inheritance
• Encapsulation
• Method overriding
• State management through class attributes

The system includes a base Vehicle class and two specialized classes:

• Car
• Plane

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2. Key Learning Objectives

• Implement inheritance using a base Vehicle class and derived classes (Car, Plane)
• Manage class attributes and constructors
• Apply method overriding, especially the toString() method
• Handle state transitions, such as maintenance tracking based on usage

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3. Class Structure

3.1 Vehicle Class (Base Class)

The Vehicle class contains attributes common to all vehicles.

3.1.1 Attributes

• make
• model
• year
• weight
• needsMaintenance (boolean, default = false)
• tripsSinceMaintenance (int, default = 0)

3.1.2 Methods

repair()

public void repair() {
    tripsSinceMaintenance = 0;
    needsMaintenance = false;
}

Resets the maintenance state of the vehicle.

3.2 Car Class (Derived Class)

The Car class extends Vehicle.

3.2.1 Additional Attributes

• isDriving (boolean)
• horsepower (int)

3.2.2 Methods

• drive()
  • Sets isDriving = true
• stop()
  • Sets isDriving = false
  • Increments tripsSinceMaintenance

Maintenance rule:

If tripsSinceMaintenance > 100
→ needsMaintenance = true

3.3 Plane Class (Derived Class)

The Plane class also extends Vehicle.

3.3.1 Additional Attributes

• isFlying (boolean)
• wingspan (float)

3.3.2 Methods

• fly()
  • Allowed only when needsMaintenance == false
  • Otherwise prints a warning message and prevents takeoff
• land()
  • Sets isFlying = false
  • Increments tripsSinceMaintenance

Maintenance rule:

If tripsSinceMaintenance > 80
→ needsMaintenance = true