Java Exercise 6

Objective:

After completing this exercise, you will be able to:

• Concept of Inheritance
• Implement a super class and sub classes in Java
• Understand the working of super class and sub class constructors

Activity:

Task 1:

Consider the following hierarchy as it exists in a university:

• There are two types of persons in the university i.e. Student and Faculty
• Every Person has some basic information that is common to all persons i.e. the first_name and last_name stored as private attributes and age which is a protected attribute.
• A student can in turn be either an Undergraduate or a Graduate student, every student has a cgpa.
• An undergraduate student has a fyp_name as his private attribute.
• A graduate student has a thesis topic as his private attribute.
• A faculty member has private attributes about the number of courses he is currently teaching, i.e. his course_count and a three digit telephone extension number. 

Implement the entire hierarchy of the Class i.e. define all the classes along with their attributes and their inheritance.

Task 2:

Add appropriate constructors to all the classes created in Exercise 2. For example the constructor for the Person class should take three inputs (for first_name, last_name and age). The student constructor should take four inputs, three for its parent class (i.e. Person) and one float value to be assigned to the cgpa attribute.

Task 3:

Add getters and setters function headings and implementation (resp) for all attributes in all the classes that you have defined.

Solution:

class Person {
    private String firstName;
    private String lastName;
    protected int age;

    public Person(String fname, String lname, int age) {
        System.out.println("Person() called");
        this.firstName = fname;
        this.lastName = lname;
        this.age = age;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

class Student extends Person {
    protected float cgpa;

    public Student(String fname, String lname, int age, float c_gpa) {
        super(fname, lname, age);
        System.out.println("Student() called");
        this.cgpa = c_gpa;
    }

    public float getCGPA() {
        return cgpa;
    }

    public void setCGPA(float cgpa) {
        this.cgpa = cgpa;
    }
}

class Undergraduate extends Student {
    private String fypName;

    public Undergraduate(String fname, String lname, int age, float c_gpa, String fyp_n) {
        super(fname, lname, age, c_gpa);
        System.out.println("Undergraduate() called");
        this.fypName = fyp_n;
    }

    public String getFYPName() {
        return fypName;
    }

    public void setFYPName(String fypName) {
        this.fypName = fypName;
    }
}

class Graduate extends Student {
    private String thesisTopic;

    public Graduate(String fname, String lname, int age, float c_gpa, String thesistopic) {
        super(fname, lname, age, c_gpa);
        System.out.println("Graduate() called");
        this.thesisTopic = thesistopic;
    }

    public String getThesisTopic() {
        return thesisTopic;
    }

    public void setThesisTopic(String thesisTopic) {
        this.thesisTopic = thesisTopic;
    }
}

class Faculty extends Person {
    private int courseCount;
    private String extensionNumber;

    public Faculty(String fname, String lname, int age, int courseCount, String extensionNumber) {
        super(fname, lname, age);
        System.out.println("Faculty() called");
        this.courseCount = courseCount;
        this.extensionNumber = extensionNumber;
    }

    public int getCourseCount() {
        return courseCount;
    }

    public void setCourseCount(int courseCount) {
        this.courseCount = courseCount;
    }

    public String getExtensionNumber() {
        return extensionNumber;
    }

    public void setExtensionNumber(String extensionNumber) {
        this.extensionNumber = extensionNumber;
    }
}

public class Main {
    public static void main(String[] args) {
        Undergraduate ted = new Undergraduate("Ted", "Thompson", 22, 3.91f, "Some FYP Name");
        Faculty richard = new Faculty("Richard", "Karp", 45, 2, "420");

        System.out.println("Undergraduate: " + ted.getFirstName() + " " + ted.getLastName() + " (" + ted.getAge() + " years old, CGPA: " + ted.getCGPA() + ", FYP Name: " + ted.getFYPName() + ")");
        System.out.println("Faculty: " + richard.getFirstName() + " " + richard.getLastName() + " (" + richard.getAge() + " years old, Teaching " + richard.getCourseCount() + " courses this semester, Extension Number: " + richard.getExtensionNumber() + ")");
    }
}