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High Level Language Lab
Lab # 06: Composition and Inheritance
Objectives:




Constructor
Object Relation
Composition
Inheritance
Instructions:
 You are allowed to use your own laptops.
 You can consult the books, manuals and class lectures.
 You should have stationary like register and ballpoint to analyze the tasks first.
 Ensure that your working environment is working properly.
 Only in practice session, consultation is allowed.
 Attempt all questions yourself and follow programming standards.
 Write down your task on register and submit your work on 13/04/2022.
High Level Language Lab
By: Mr. Uzair Saeed
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Introduction
In OOP, various kinds of relationships (i.e. inheritance, association and composition) exist between
various classes/objects. Inheritance is modeled as is-a relationship. Inheritance exists between classes
and main goal of inheritance is make object that would represent specialized version of original
objects. For example, a car is vehicle, student is person etc.
On the other hand, association and aggregation/composition represent uses-a and has-a relationship,
respectively between objects. It is based on the object-oriented design where an object can acquire
properties of another objects. In advance, aggregation and composition are two types of association
representing weak and strong relationship. Composition is special kind of aggregation which
represents ownership between objects along with the existence of life-cycle dependency. A
department employee relationship is an example of aggregation whereas university-department
relationship is an example of composition.
Experiment 1: Department/Employee (Use of Composition)
//
//
//
//
//
//
//
File: MyMain.java
Version: V1.0
Date: 05-04-2022
Name: Uzair Saeed
ID:
BS-Teacher-01
This is runnable class for Department
Demonstrate use of composition
public class MyMain
{
public static void main(String[] args)
{
Department cs = new Department("Computational Sciences");
cs.DepInfo();
}
}
//File: Department.java
//Version: V1.0
//Date: 05-04-2022
//Name: Uzair Saeed
//ID:
BS-Teacher-01
//This is department class which contain name and teacher info
class Department{
private String depName;//store department name
private Teacher[] teacher;//teacher object composition
public Department(String depName) {
High Level Language Lab
By: Mr. Uzair Saeed
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this.depName = depName;
teacher = new Teacher[2];//adding two teacher in department
teacher[0] = new Teacher("Ehsan",2,3,2020);
teacher[1] = new Teacher("Naveed",31,1,2022);
}
//method for displaying department info
public void DepInfo() {
System.out.print("Department : "+depName);
System.out.print(" has following faculty ");
for(int i = 0 ; i<teacher.length;i++) {
System.out.println("\n\n");//adding new line
System.out.print(i+1);
teacher[i].TeacherInfo();//calling teacher method
}
}
}
//File: Teacher.java
//Version: V1.0
//Date: 05-04-2022
//Name: Uzair Saeed
//ID:
BS-Teacher-01
//This is teacher class which contain name and joining date
class Teacher{
private String name;//store teacher name
private Date joiningDate;//composition of Date class object
//paramerterize constructor of date class
public Teacher(String name, int day, int month, int year) {
this.name = name;
//calling date parameterize constructor
this.joiningDate = new Date(day,month, year);
}
//method for displaying TeacherInfo
public void TeacherInfo() {
System.out.print("
Name :"+name);
joiningDate.JoinInfor();//calling date public method
}
}
//File: Date.java
//Version: V1.0
//Date: 05-04-2022
//Name: Uzair Saeed
//ID:
BS-Teacher-01
//This is date class which contain date, month and year
High Level Language Lab
By: Mr. Uzair Saeed
Page |4
class Date{
private int day;//hold day of month
private int month;//store month
private int year;//hold year
//paramerterize constructor of date class
public Date(int day, int month, int year) {
this.day = day;
this.month = month;
this.year = year;
}
//method for displaying joining date
public void JoinInfor() {
System.out.print("
Joining Date:
"+day+"/"+month+"/"+year);
}
}
Experiment 2: Employee Program (Use of inheritance)
// File: TestEmployee.java
// Version: V1.0
// Date: 05-04-2022
// Name: Uzair Saeed
// ID:
BS-Teacher-01
// This is runnable class for Employee
// Demonstrate use of inheritance
public class TestEmployee {
public static void main(String args[]) {
SalaryComEmployee ali = new
SalaryComEmployee("Muhammad","Ali","33100-222",100,0.1f,5000);
ComissionEmployee majid = new
ComissionEmployee("Majid","Khan","33101-45",500,0.5f);
System.out.println("Salried Employee Detail ");
System.out.println(ali);//call toString method
System.out.println("Total Earning "+ali.earnings());
High Level Language Lab
By: Mr. Uzair Saeed
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System.out.println("\n\nCommission Employee Detail ");
System.out.println(majid);//call toString method
System.out.println("Total Earning "+majid.earnings());
System.out.println("\n\nChanging Ali Data");
ali.setFirstName("Waqas");
ali.setLastName("Jadon");
ali.setSalary(-200);//invalid data
System.out.println("Salried Employee Detail ");
System.out.println(ali);//call toString method
System.out.println("Total Earning "+ali.earnings());
}
}
//File: Employee.java
//Version: V1.0
//Date: 05-04-2022
//Name: Uzair Saeed
//ID:
BS-Teacher-01
//This is Employee which define first, last name and cnic
//Employee is parent class demonstrate use of inheritance
class Employee{
private String firstName;//store firstName
private String lastName;//store lastName
private String cnic;//store cnic
public Employee(String first, String last, String cnic) {
firstName = first;
lastName = last;
this.cnic = cnic;
}
//getters and setters
//which enforce encapsulation
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;
}
High Level Language Lab
By: Mr. Uzair Saeed
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public String getCnic() {
return cnic;
}
public void setCnic(String cnic) {
this.cnic = cnic;
}
//toString is built-in method in java lang
//performing method overriding
//will call this method on object
@Override
public String toString() {
String str = "First name is "+getFirstName();
str += "\nLast Name is "+getLastName();
str +="\nCnic is "+getCnic();
return str;
}
}
//File: ComissionEmployee.java
//Version: V1.0
//Date: 05-04-2022
//Name: Uzair Saeed
//ID:
BS-Teacher-01
//This is ComissionEmployee which define sale and commission
//ComissionEmployee is child class inherit properties of Employee
class ComissionEmployee extends Employee{
private float grosSale;//weekly sale
private float comRate;//commission rate
public ComissionEmployee(String first, String last, String cnic,
float sale, float rate) {
super(first, last, cnic);//call parent class constructor
setGrosSale(sale);//calling gross sale setter
setComRate(rate);//commission rate setter
}
//getters and setters
//which enforce encapsulation
public float getGrosSale() {
return grosSale;
}
public void setGrosSale(float sale) {
if(sale > 0)//validate sale must be greater than zero
grosSale = sale;
}
public float getComRate() {
return comRate;
High Level Language Lab
By: Mr. Uzair Saeed
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}
public void setComRate(float rate) {
if(rate > 0 && rate <= 1)//validate rate between 0 and 1
comRate = rate;
}
//earning method return earing of commission employee
public float earnings() {
return getComRate()*getGrosSale();
}
//toString is built-in method in java lang
//performing method overriding
//will call this method on object
@Override
public String toString() {
String str=super.toString();//employee class toString method
str += "\nGross Sale is "+getGrosSale();
str +="\nCommission Rate is "+getComRate();
return str;
}
}
//File: SalaryComEmployee.java
//Version: V1.0
//Date: 05-04-2022
//Name: Uzair Saeed
//ID:
BS-Teacher-01
//This is SalaryComEmployee which define monthly salary
//SalaryComEmployee is child class inherit properties of
ComissionEmployee
class SalaryComEmployee extends ComissionEmployee{
private int salary;//monthly salary
public SalaryComEmployee(String first, String last, String cnic,
float sale, float rate, int salary) {
super(first, last, cnic,sale,rate);//call parent class
constructor
setSalary(salary);
}
//getters and setters
//which enforce encapsulation
public int getSalary() {
return salary;
}
High Level Language Lab
By: Mr. Uzair Saeed
Page |8
public void setSalary(int salary) {
if(salary > 0)//validate salary must be greater than zero
this.salary = salary;//assigning salary
}
//earning method return earing of salaried employee
public float earnings() {
return salary+super.earnings();
}
//toString is built-in method in java lang
//performing method overriding
//will call this method on object
@Override
public String toString() {
String str=super.toString();//employee class toString method
str += "\nMonthly Salary is "+getSalary();
return str;
}
}
Salried Employee Detail
First name is Muhammad
Last Name is Ali
Cnic is 33100-222
Gross Sale is 100.0
Commission Rate is 0.1
Monthly Salary is 5000
Total Earning 5010.0
Commission Employee Detail
First name is Majid
Last Name is Khan
Cnic is 33101-45
Gross Sale is 500.0
Commission Rate is 0.5
Total Earning 250.0
Changing Ali Data
Salried Employee Detail
First name is Waqas
Last Name is Jadon
High Level Language Lab
By: Mr. Uzair Saeed
Page |9
Cnic is 33100-222
Gross Sale is 100.0
Commission Rate is 0.1
Monthly Salary is 5000
Total Earning 5010.0
Task 1: University System (Object Relationship)
Consider six classes i.e. Person, Professor, Researcher, Department, Laboratory and University
has following specifications.
Class University has
 Two attributes of string i.e. universityName and location.
 An attribute named dept from Department
Class Department has
 Two attributes i.e. deptId and depName.
 A constructor overloading to initialize date fields
 A method display() to show all attributes
Class Laboratory contains
 Two attributes labId and experimentNo.
 A constructor overloading to initialize date fields
Class Person has
 Two attributes of i.e. name and age.
 A constructor overloading to initialize date fields
 A method display() to show all attributes
Class Professor is a Person and has
 Attributes of profId.
 Attributes of dept of type Department.
 A constructor overloading to initialize date fields
 A method display() to show all attributes
Class Researcher is a Professor and has
 A data field named lab of type Laboratory
 A constructor overloading to initialize date fields
 A method display() to show all attributes
a) Draw UML diagram for each class and show inheritance
between these classes
and composition relationship
b) Implement all these classes in Java while illustrating concept of inheritance and composition.
High Level Language Lab
By: Mr. Uzair Saeed