HANDS ON JAVA(OOP - based uses) (Part-IV)

            Practice JAVA like Never Before!

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Day 4 🔥

Objective

Learning to implement menu-driven programs, overloading methods and constructors:-

1. Design a class to represent a Bank Account. Include the following things:

Fields

• Name of the depositor

• Address of the depositor

• Account number

• Balance amount in the account

Methods

• To assign initial values

• To deposit an amount

• To withdraw an amount after checking balance

• To display the name, address, and balance of a customer

From the main() method create an object and call these methods.

• Program

import java.util.Scanner;

class BankAcc{

String name, address;

long acc_no;

double balance;

BankAcc(String p, String q, long r, double s){

name = p;

address = q;

acc_no = r;

balance = s;

}

void deposit(double x){

System.out.println("Pre-existing Balance = "+balance);

balance += x;

System.out.println("Amount Deposited = "+x);

System.out.println("New Balance = "+balance);

}

void withdraw(double x){

System.out.println("Pre-existing Balance = "+balance);

balance -= x;

System.out.println("Amount Withdrawn = "+x);

System.out.println("New Balance = "+balance);

}

void display(){

System.out.println("Your(Account Holder) name is "+name+". \nYour"+

"account number is "+acc_no+". \nYour address is "+address+

". \nYour present balance = "+balance);

}

}//end class

class Main{

public static void main(String[] args){

Scanner sc = new Scanner(System.in);

System.out.println("Enter your name:- ");

String name = sc.nextLine();

System.out.println("Enter your address:- ");

String add = sc.nextLine();

System.out.println("Enter your account number:- ");

long num = sc.nextLong();

System.out.println("Enter your initial balance:- ");

double bal = sc.nextDouble();

//creating and initializing an instance of class: BanAcc :-

BankAcc ob = new BankAcc(name, add, num, bal);

//MENU:-

System.out.println("OPTIONS MENU:\nEnter \'1\' to deposit money\n"+

"\'2\' to withdraw money\n\'3\' to see account info and \n\'-1\'"+

" to EXIT");

//running infinitely until user wants to break:-

int n, flag=1;

double temp;

while(flag==1){

System.out.println("\nEnter Your Choice:- ");

n = sc.nextInt();

switch(n){

case 1:

System.out.println("Enter the deposit amount:- ");

temp = sc.nextDouble();

ob.deposit(temp);

break;

case 2:

System.out.println("Enter the withdraw amount:- ");

temp = sc.nextDouble();

ob.withdraw(temp);

break;

case 3:

ob.display();

break;

case 4:

System.out.println("Thank You ^_^");

flag=0;

break;

default:

System.out.println("Invalid Choice! \nPlease try again.");

}//end switch case

}//end while

}//end main()

}//end class

• Output:

       

---------------------------------------------------

2. Create a class and determine if method overloading holds good for the return type of methods or not.

• Program:

Observation: Method overloading does not work if two methods are different only in terms of their return type.

Reason: when it’s called, it creates confusion on which function is being called since the no. of parameters and their data types are identical.

This is an example:-

class Operate{
int add(int p, int q){
return p+q;
}
double add(int p, int q){
return p+q;
}
}//end class

class Main{
public static void main(String[] args){
Operate obj = new Operate();
int n1 = obj.add(2, 3);
double n2 = obj.add(2, 7);
System.out.println("1st sum = "+n1+" and 2nd sum = "+n2);
}
}

            Error:- 

Solution: For method overloading to hold good,

having only different return types will not help.  

We need either:-

i> different data types of parameters:-

class Operate{

int add(int p, int q){

return p+q;

}

double add(double p, double q){

return p+q;

}

}//end class

class Main{

public static void main(String[] args){

Operate obj = new Operate();

int n1 = obj.add(2, 3);

double n2 = obj.add(100, 7.9);

System.out.println("1st sum = "+n1+" and 2nd sum = "+n2); 

        }

}

• Output:

ii> different no. of parameters:-

class Operate{

int add(int p, int q){

return p+q;

}

double add(int p, int q, int r){

return p+q+r;

}

}//end class

class Main{

public static void main(String[] args){

Operate obj = new Operate();

int n1 = obj.add(2, 3);

double n2 = obj.add(100, 7, 250);

System.out.println("1st sum = "+n1+" and 2nd sum = "+n2);

}

}

• Output:

---------------------------------------------------

3. Overload the constructors for classes Cuboid and Rectangle of a rectangular figure and display its area and volume. Rectangle is the superclass and Cuboid is the subclass.

• Program:

import java.util.Scanner;

//Superclass:-

class Rectangle{

double len, breadth;

Rectangle(double l, double b){

this.len = l;

this.breadth = b;

}

double area(){

return len*breadth;

}

}

//Sub-class:-

class Cuboid extends Rectangle{

double height;

Cuboid(double l, double b, double h){

super(l, b);//parent class constructor call from child class

this.height = h;

}

double vol(){

return area()*height;

}

}

class Main{

public static void main(String[] args){

Scanner sc=new Scanner(System.in);

double l, b, h;

System.out.println("Enter length: ");

l = sc.nextDouble();

System.out.println("Enter breadth: ");

b = sc.nextDouble();

System.out.println("Enter height: ");

h = sc.nextDouble();

Cuboid obj = new Cuboid(l, b, h);

System.out.println("Area of Rectangle: "+obj.area());

System.out.println("Volume of Cuboid: "+obj.vol());

}

}

• Output:

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<---------- End of Part - IV ---------->😋