Week 5 Practice Questions - Object Oriented
Programming Paradigm
1. Abstraction
Qn 1: Create an abstract class Animal with abstract methods make Sound() and
eat().Create subclasses Dog, Cat, and Bird that inherit from Animal and
implement the abstract
methods accordingly.
abstract class Animal
{
public abstract void sound();
public abstract void eat();
}
class Dog extends Animal
{
public void sound()
{
System.out.println("Barking");
}
public void eat()
{
System.out.println("Dog is eating");
}
}
class Cat extends Animal
{
public void sound()
{
System.out.println("Meowing");
}
public void eat()
{
System.out.println("Cat is eating");
}
}
class Bird extends Animal
{
public void sound()
{
System.out.println("Chirping");
}
public void eat()
{
System.out.println("Bird is eating");
}
}
public class Animals
{
public static void main(String[] args) {
Dog dog = new Dog();
Cat cat = new Cat();
Bird bird = new Bird();
dog.sound();
dog.eat();
cat.sound();
cat.eat();
bird.sound();
bird.eat();
}
}
Output:
Qn 2: Create an abstract class Shape with abstract methods calculateArea()
and calculatePerimeter(). Create subclasses Circle, Rectangle, and Triangle
that inherit from
Shape and implement the abstract methods accordingly.
abstract class Shape
{
public abstract double Area();
public abstract double Perimeter();
}
class Circle extends Shape
{
int radius;
Circle(int r)
{
radius = r;
}
public double Area()
{
return radius*radius;
}
public double Perimeter()
{
return 2*3.14*radius;
}
}
class Rectangle extends Shape
{
int length,width; Rectangle(int
l,int w)
{
length = l;
width = w;
}
public double Area()
{
return length*width;
}
public double Perimeter()
{
return 2*(length+width);
}
}
class Triangle extends Shape
{
int height,base,side1,side2; Triangle(int h,int
b,int s1,int s2)
{
height=h;
base=b;
side1=s1;
side2=s2;
}
public double Area()
{
return (height*base)/2;
}
public double Perimeter()
{
return base+side1+side2;
}
}
public class Shapes
{
public static void main(String args[])
{
Circle c=new Circle(5);
System.out.println("Area of Circle: "+c.Area());
System.out.println("Perimeter of Circle: "+c.Perimeter());
Rectangle r=new Rectangle(5,6);
System.out.println("Area of Rectangle: "+r.Area());
System.out.println("Perimeter of Rectangle: "+r.Perimeter());
Triangle t= new Triangle(10, 8, 7, 6);
System.out.println("Area of Triangle: "+t.Area());
System.out.println("Perimeter of Triangle: "+t.Perimeter());
}
}
Output:
Qn 3: Create an abstract class Employee with abstract methods
calculateSalary() andgetEmployeeDetails(). Create subclasses
RegularEmployee, ContractEmployee, and HourlyEmployee that inherit from
Employee and implement the abstract methods Accordingly
abstract class Employee {
String name;
int id;
public Employee(String name, int id) {
this.name = name;
this.id = id;
}
abstract double calculateSalary();
abstract String getEmployeeDetails();
}
class RegularEmployee extends Employee {
double basicSalary;
double bonus;
public RegularEmployee(String name, int id, double basicSalary, doublebonus) {
super(name, id); this.basicSalary =
basicSalary;this.bonus = bonus;
}
@Override
double calculateSalary() { return
basicSalary + bonus;
}
@Override
String getEmployeeDetails() {
return "Regular Employee: " + name + ", ID: " + id + ", Salary: " +calculateSalary();
}
}
class ContractEmployee extends Employee {double
contractAmount;
public ContractEmployee(String name, int id, double contractAmount) {super(name,
id);
this.contractAmount = contractAmount;
}
@Override
double calculateSalary() {return
contractAmount;
}
@Override
String getEmployeeDetails() {
return "Contract Employee: " + name + ", ID: " + id + ", ContractAmount: " +
calculateSalary();
}
}
class HourlyEmployee extends Employee {
double hourlyRate;
int hoursWorked;
public HourlyEmployee(String name, int id, double hourlyRate, int
hoursWorked) {
super(name, id); this.hourlyRate =
hourlyRate; this.hoursWorked =
hoursWorked;
}
@Override
double calculateSalary() {
return hourlyRate * hoursWorked;
}
@Override
String getEmployeeDetails() {
return "Hourly Employee: " + name + ", ID: " + id + ", Hours Worked: "
+ hoursWorked + ", Salary: " + calculateSalary();
}
}
public class Employees {
public static void main(String[] args) {
Employee regEmp = new RegularEmployee("John Mark", 101, 50000, 5000);
Employee contEmp = new ContractEmployee("Jane Smith", 102, 60000); Employee
hourEmp = new HourlyEmployee("Mark Johnson", 103, 50, 160);
System.out.println(regEmp.getEmployeeDetails());
System.out.println(contEmp.getEmployeeDetails());
System.out.println(hourEmp.getEmployeeDetails());
}
}
Output:
II. Polymorphism
Qn 1: Create a hierarchy of animals with classes like Animal, Mammal, Bird,
and Fish. Implement polymorphism to demonstrate different animal sounds.
Hint:
Create an abstract class Animal with an abstract method makeSound().
Create subclasses Mammal, Bird, and Fish, inheriting from Animal and
overriding the makeSound() method.
Create an array of Animal objects to store different types of animals.
Iterate through the array and call the makeSound() method for each animal,
demonstrating polymorphism.
abstract class Animal {
String name;
public Animal(String name) {
this.name = name;
}
abstract void makeSound();
}
class Mammal extends Animal {
public Mammal(String name) {
super(name);
}
@Override
void makeSound() {
System.out.println(name + " says: Roar!");
}
}
class Bird extends Animal {
public Bird(String name) {
super(name);
}
@Override
void makeSound() {
System.out.println(name + " says: Tweet!");
}
}
class Fish extends Animal {
public Fish(String name) {
super(name);
}
@Override
void makeSound() {
System.out.println(name + " says: Blub!");
}
}
public class Animals {
public static void main(String[] args) {Animal[]
animals = new Animal[3]; animals[0] = new
Mammal("Lion"); animals[1] = new
Bird("Sparrow"); animals[2] = new
Fish("Goldfish");
for (Animal animal : animals) {
animal.makeSound();
}
}
}
Output:
Qn 2: Overload
Create a Calculator class with multiple calculate () methods that take different
combinations of arguments (e.g., calculate (int, int), calculate (double,
double), calculate (int, int, char)). Implement these methods to perform
different arithmeticoperations based on the arguments.
public class Calculator {
public int calculate(int a, int b) {
return a + b;
}
public double calculate(double a, double b) {
return a + b;
}
public int calculate(int a, int b, char operator) {
switch (operator) {
case '+':
return a + b;
case '-':
return a - b;
case '*':
return a * b;
case '/':
if (b != 0) {
return a / b;
} else {
throw new ArithmeticException("Division by zero is not
allowed.");
}
default:
throw new IllegalArgumentException("Invalid operator");
}
}
public static void main(String[] args) {
Calculator calc = new Calculator();
System.out.println("Sum of 10 and 20 (int): " + calc.calculate(10,
20));
System.out.println("Sum of 5.5 and 2.3 (double): " +
calc.calculate(5.5, 2.3));
System.out.println("Product of 10 and 20 (int with operator): " +
calc.calculate(10, 20, '*'));
System.out.println("Division of 10 and 2 (int with operator): " +
calc.calculate(10, 2, '/'));
}
}
Output:
Qn 3: Override
Create a base class Calculator with a calculate () method that takes two double
arguments.
Implement this method to perform addition. Create subclasses SubtractionCalculator,
MultiplicationCalculator, and DivisionCalculator that inherit from Calculator
andoverride
the calculate () method to perform their respective arithmetic operations.
class Calculator {
public double calculate(double a, double b) {
return a + b;
}
}
class SubtractionCalculator extends Calculator {
@Override
public double calculate(double a, double b) {return a -
b;
}
}
class MultiplicationCalculator extends Calculator {
@Override
public double calculate(double a, double b) {return a *
b;
}
}
class DivisionCalculator extends Calculator {
@Override
public double calculate(double a, double b) {if (b != 0) {
return a / b;
} else {
throw new ArithmeticException("Division by zero is not allowed.");
}
}
}
public class Calculators {
public static void main(String[] args) { Calculator
addCalc = new Calculator();
Calculator subCalc = new SubtractionCalculator(); Calculator
mulCalc = new MultiplicationCalculator();Calculator divCalc =
new DivisionCalculator();
System.out.println("Addition: " + addCalc.calculate(10, 5));
System.out.println("Subtraction: " + subCalc.calculate(10, 5));
System.out.println("Multiplication: " + mulCalc.calculate(10, 5));
System.out.println("Division: " + divCalc.calculate(10, 5));
}
}
Output:
III. Inheritance
Qn 1: Base Class: Animal
➢ Attributes: name, sound, num_legs
➢ Methods: make_sound(),
walk() Derived Classes:
➢ Dog: barks
➢ Cat: meows
➢ Bird: chirps,
fliesQuestions:
1. Create a base class Animal with the specified attributes and methods.
2. Create derived classes Dog, Cat, and Bird that inherit from Animal.
3. Override the make_sound() and walk() methods in each derived class to
providespecific
implementations.
4. Create objects of each derived class and demonstrate their behavior
(e.g., call make_sound() and walk() methods).
// Base class Animal
class Animal {
String name;
String sound;
int num_legs;
// Constructor
public Animal(String name, String sound, int num_legs) {this.name =
name;
this.sound = sound; this.num_legs =
num_legs;
}
// Method to make sound public
void make_sound() {
System.out.println(name + " makes a sound: " + sound);
}
// Method to walk public
void walk() {
System.out.println(name + " walks on " + num_legs + " legs.");
}
}
// Subclass Dog
class Dog extends Animal {
// Constructor
public Dog(String name) { super(name,
"barks", 4);
}
// Override make_sound() method
@Override
public void make_sound() {
System.out.println(name + " barks: Woof Woof!");
}
// Override walk() method
@Override
public void walk() {
System.out.println(name + " walks on " + num_legs + " legs, waggingits tail.");
}
}
// Subclass Cat
class Cat extends Animal {
// Constructor
public Cat(String name) { super(name,
"meows", 4);
}
// Override make_sound() method
@Override
public void make_sound() {
System.out.println(name + " meows: Meow Meow!");
}
// Override walk() method
@Override
public void walk() {
System.out.println(name + " walks gracefully on " + num_legs + "legs.");
}
}
// Subclass Bird
class Bird extends Animal {
// Constructor
public Bird(String name) { super(name,
"chirps", 2);
}
// Override make_sound() method
@Override
public void make_sound() {
System.out.println(name + " chirps: Tweet Tweet!");
}
// Override walk() method
@Override
public void walk() {
System.out.println(name + " hops on " + num_legs + " legs andflies.");
}
}
// Main class to test the implementationpublic
class Animals {
public static void main(String[] args) {
// Create objects of derived classesAnimal
dog = new Dog("Buddy"); Animal cat = new
Cat("Whiskers"); Animal bird = new
Bird("Tweety");
// Demonstrate behavior
dog.make_sound();
dog.walk();
cat.make_sound();
cat.walk();
bird.make_sound();
bird.walk();
}
}
Output:
Qn 2: Consider a vehicle hierarchy with a base class Vehicle that has attributes
like make,
model, year, and num_wheels. We want to create derived classes Car, Truck,
andMotorcycle
that inherit from Vehicle and have additional specific attributes and methods.
Additionally, we
want to introduce another base class Engine with attributes like type,
horsepower, and
fuel_type, and have Car, Truck, and Motorcycle inherit from both Vehicle and
Engine.Implement using multiple inheritance.
class Vehicle {
String make;
String model;
int year;
int num_wheels;
public Vehicle(String make, String model, int year, int num_wheels) {
this.make = make;
this.model = model;
this.year = year;
this.num_wheels = num_wheels;
}
public void displayVehicleInfo() { System.out.println("Make: " + make);
System.out.println("Model: " + model); System.out.println("Year: "
+ year); System.out.println("Number of Wheels: " + num_wheels);
}
}
interface Engine { String
getType(); int
getHorsepower();
String getFuelType();
}
class Car extends Vehicle implements Engine {String
engineType;
int horsepower;
String fuelType;int
numDoors;
public Car(String make, String model, int year, int num_wheels, StringengineType, int
horsepower, String fuelType, int numDoors) {
super(make, model, year, num_wheels);
this.engineType = engineType;
this.horsepower = horsepower; this.fuelType
= fuelType; this.numDoors = numDoors;
}
@Override
public String getType() {return
engineType;
}
@Override
public int getHorsepower() {return
horsepower;
}
@Override
public String getFuelType() {return
fuelType;
}
public void displayCarInfo() {
displayVehicleInfo();
System.out.println("Engine Type: " + getType());
System.out.println("Horsepower: " + getHorsepower());
System.out.println("Fuel Type: " + getFuelType());
System.out.println("Number of Doors: " + numDoors);
}
}
class Truck extends Vehicle implements Engine {String
engineType;
int horsepower;
String fuelType; int
loadCapacity;
public Truck(String make, String model, int year, int num_wheels, StringengineType, int
horsepower, String fuelType, int loadCapacity) {
super(make, model, year, num_wheels);
this.engineType = engineType;
this.horsepower = horsepower; this.fuelType
= fuelType; this.loadCapacity = loadCapacity;
}
@Override
public String getType() {return
engineType;
}
@Override
public int getHorsepower() {return
horsepower;
}
@Override
public String getFuelType() {return
fuelType;
}
public void displayTruckInfo() {
displayVehicleInfo();
System.out.println("Engine Type: " + getType()); System.out.println("Horsepower: " +
getHorsepower()); System.out.println("Fuel Type: " + getFuelType());
System.out.println("Load Capacity: " + loadCapacity + " kg");
}
}
class Motorcycle extends Vehicle implements Engine {String
engineType;
int horsepower; String
fuelType; boolean
hasSidecar;
public Motorcycle(String make, String model, int year, int num_wheels,String
engineType, int horsepower, String fuelType, boolean hasSidecar) {
super(make, model, year, num_wheels);
this.engineType = engineType;
this.horsepower = horsepower; this.fuelType
= fuelType; this.hasSidecar = hasSidecar;
}
@Override
public String getType() {return
engineType;
}
@Override
public int getHorsepower() {return
horsepower;
}
@Override
public String getFuelType() {return
fuelType;
}
public void displayMotorcycleInfo() {
displayVehicleInfo();
System.out.println("Engine Type: " + getType()); System.out.println("Horsepower: " +
getHorsepower()); System.out.println("Fuel Type: " + getFuelType());
System.out.println("Has Sidecar: " + (hasSidecar ? "Yes" : "No"));
}
}
public class Vehicles {
public static void main(String[] args) {
Car car = new Car("Toyota", "Corolla", 2020, 4, "V6", 300, "Petrol",
4);
Truck truck = new Truck("Ford", "F-150", 2019, 4, "V8", 400, "Diesel",
1000);
Motorcycle motorcycle = new Motorcycle("Harley-Davidson", "Iron 883",
2021, 2, "V-Twin", 70, "Petrol", false);
System.out.println("Car Details:");
car.displayCarInfo();
System.out.println("\nTruck Details:");
truck.displayTruckInfo();
System.out.println("\nMotorcycle Details:");
motorcycle.displayMotorcycleInfo();
}
}
Output:
IV. Encapsulation
Qn 1: A bank wants to create a class to represent bank accounts. Each
accountshould have a
unique account number, an initial balance, and methods to deposit and
withdrawfunds. The
bank wants to ensure that the account balance is always positive and that
withdrawals do not
exceed the balance.
➢ Create a class named BankAccount with private attributes for
accountNumber, balance,
and a constant for the minimum balance allowed.
➢ Implement public getter and setter methods for the accountNumber attribute.
➢ Implement public methods deposit and withdraw that update the
balanceappropriately,
ensuring that the balance remains positive and that withdrawals do not exceed
the balance.
class BankAccount {
// Private attributes
private String accountNumber;
private double balance;
private static final double MIN_BALANCE = 0.0; // Minimum balance allowed
// Constructor
public BankAccount(String accountNumber, double initialBalance) {
this.accountNumber = accountNumber;
if (initialBalance >= MIN_BALANCE) {
this.balance = initialBalance;
} else {
throw new IllegalArgumentException("Initial balance cannot be
negative.");
}
}
// Public getter for accountNumber
public String getAccountNumber() {
return accountNumber;
}
// Public setter for accountNumber
public void setAccountNumber(String accountNumber) {
this.accountNumber = accountNumber;
}
// Public method to deposit funds public
void deposit(double amount) {
if (amount > 0) { balance
+= amount;
System.out.println("Deposited: $" + amount + ". New balance: $" +
balance);
} else {
throw new IllegalArgumentException("Deposit amount must be
positive.");
}
}
// Public method to withdraw funds public
void withdraw(double amount) {
if (amount > 0) {
if (balance - amount >= MIN_BALANCE) {
balance -= amount;
System.out.println("Withdrew: $" + amount + ". New balance: $"
+ balance);
} else {
System.out.println("Insufficient funds. Withdrawal denied.");
}
} else {
throw new IllegalArgumentException("Withdrawal amount must be
positive.");
}
}
// Public getter for balancepublic
double getBalance() {
return balance;
}
}
public class Bank {
public static void main(String[] args) {
// Create a new bank account with an initial balance
BankAccount account = new BankAccount("123456789", 500.00);
// Display account details
System.out.println("Account Number: " + account.getAccountNumber());
System.out.println("Initial Balance: $" + account.getBalance());
// Deposit funds
account.deposit(150.00);
// Withdraw funds
account.withdraw(200.00);
// Attempt to withdraw more funds than available
account.withdraw(600.00);
// Display final balance
System.out.println("Final Balance: $" + account.getBalance());
}
}
Output:
Qn 2: Write a Java program to create a class called Rectangle with private
instancevariables
length and width. Provide public getter and setter methods to access and
modifythese
variables.
class Rectangle {
// Private instance variables
private double length;
private double width;
// Constructor to initialize the length and width
public Rectangle(double length, double width) {
this.length = length;
this.width = width;
}
// Default constructor
public Rectangle() {
this.length = 0.0;
this.width = 0.0;
}
// Getter for length
public double getLength() {return
length;
}
// Setter for length
public void setLength(double length) {if
(length > 0) {
this.length = length;
} else {
System.out.println("Length must be positive.");
}
}
// Getter for width
public double getWidth() {
return width;
}
// Setter for width
public void setWidth(double width) {if
(width > 0) {
this.width = width;
} else {
System.out.println("Width must be positive.");
}
}
// Method to calculate the area of the rectanglepublic
double calculateArea() {
return length * width;
}
// Method to calculate the perimeter of the rectanglepublic
double calculatePerimeter() {
return 2 * (length + width);
}
// Method to display the details of the rectanglepublic void
displayRectangleInfo() {
System.out.println("Length: " + length); System.out.println("Width: " +
width); System.out.println("Area: " + calculateArea());
System.out.println("Perimeter: " + calculatePerimeter());
}
}
public class Rectangles {
public static void main(String[] args) {
// Create a Rectangle object using the parameterized constructor
Rectangle rect1 = new Rectangle(5.0, 3.0);
rect1.displayRectangleInfo();
// Modify the length and width using setter methods
rect1.setLength(7.5);
rect1.setWidth(4.0);
System.out.println("\nAfter modifying length and width:");
rect1.displayRectangleInfo();
// Create a Rectangle object using the default constructor
Rectangle rect2 = new Rectangle();
System.out.println("\nDefault Rectangle:");
rect2.displayRectangleInfo();
// Set length and width for the default rectangle
rect2.setLength(6.0);
rect2.setWidth(2.5);
System.out.println("\nAfter setting length and width:");
rect2.displayRectangleInfo();
}
}
Output:
Rohit N Rajput
RA2311033010119
AK-2
