Explanation of the Code:

This java program is a Simple Calculator that allows users to perform addition, subtraction, multiplication, and division. The program runs in a loop, allowing the user to perform multiple calculations until they decide to exit.

Step-by-Step Explanation:

1. Importing Scanner Class

import java.util.Scanner;

- The Scanner class is imported from java.util to read input from the user.

2. Creating the Class

class simplecalculator {

- A class named simplecalculator is created.

- It follows java naming conventions, but the class name should start with an uppercase letter (e.g., SimpleCalculator).

3. Main Method

public static void main(String[] args) {

- The main method is the entry point of the program.

- Inside the main method, we initialize the Scanner object.

4. Creating Scanner Object

Scanner userinput = new Scanner(System.in);

- Scanner object userinput is created to take input from the user.

5. Infinite While Loop

while(true) {

- This loop runs indefinitely, allowing the user to perform multiple calculations.

- The loop will only exit when the user selects 0.

6. Displaying Calculator Header

System.out.println(" \n -");

System.out.println(" | Simple Calculator |");

System.out.println(" -");

- The header is displayed to make the calculator look structured and user-friendly.

7. Displaying the List of Operations

System.out.println("\nselect your choice of operation from the below options (1 - 4)numbers only:");

System.out.println("-");

System.out.println("1.)Addition\n2.)substraction\n3.)multplication\n4.)division");

System.out.println("enter your choice from (1- 4) : ");

- The available mathematical operations are displayed for the user.

8. Checking for Invalid Input (Non-Numeric Values)

if(!userinput.hasNextInt()) {

System.out.println(" Invalid Input : you cannot select non - numeric values ");

System.out.println("\nselect your choice of operation from the options (1 - 4)numbers only:");

userinput.next(); // Clear the invalid input

continue; // Restart the loop again.

}

- If the user enters a non-numeric value (like a letter or symbol), an error message is displayed.

- The invalid input is cleared using userinput.next(), and the loop restarts.

9. Taking User Input for Choice

int choice = userinput.nextInt();

- The program reads the user's choice for the operation.

10. Exit Condition

if(choice == 0) {

System.out.println(" Thank you for using simple calculator. !!! GOODBYE !!!");

break; // Exits the loop

}

- If the user enters 0, the program exits.

11. Handling Invalid Choice

if (choice > 4) {

System.out.println("Invalid choice! Please select a valid option.");

continue; // Restart the loop again.

}

- If the user enters a number greater than 4, an error message is displayed.

12. Reading the First Number

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

if (!userinput.hasNextDouble()) {

System.out.println("Invalid input! Please enter a valid number.");

userinput.next(); // Clear invalid input

continue; // Restart the loop

}

double num1 = userinput.nextDouble();

- The program asks the user to enter the first number.

- If the user enters a non-numeric value, an error message is shown, and the loop restarts.

13. Reading the Second Number

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

if (!userinput.hasNextDouble()) {

System.out.println("Invalid input! Please enter a valid number.");

userinput.next(); // Clear invalid input

continue; // Restart the loop

}

double num2 = userinput.nextDouble();

- The program asks the user to enter the second number.

- Again, input validation ensures that only numeric values are accepted.

14. Performing the Selected Operation

double result;

- The result variable is declared to store the output of the calculation.

Addition

if(choice==1){ // ADDITION

result = num1+num2;

System.out.println("The addition of "+num1+" + "+num2+" = "+result);

}

- If the user selects 1, the program adds num1 and num2.

Subtraction

else if(choice==2){ // SUBTRACTION

result = num1-num2;

System.out.println("The Subtraction of "+num1+" - "+num2+" = "+result);

}

- If the user selects 2, the program subtracts num2 from num1.

Multiplication

else if(choice==3){ // MULTIPLICATION

result = num1 * num2;

System.out.println("The Multiplication of "+num1+" "+num2+" = "+result);

}

- If the user selects 3, the program multiplies num1 and num2.

Division

else if(choice==4){ // DIVISION

if(num1==0 || num2==0){

System.out.println("Error : Division by zero is not allowed.");

}

else {

result = num1/num2;

System.out.println("The Division of "+num1+" / "+num2+" = "+result);

}

}

- If the user selects 4, the program divides num1 by num2.

- If num2 == 0, an error message prevents division by zero.

15. Closing the Scanner

userinput.close();

- The Scanner is closed to prevent memory leaks.

Summary of Features

✅ Handles multiple calculations using a while loop.

✅ Prevents crashes from invalid input (letters, symbols, etc.).

✅ Allows the user to exit the calculator with 0.

✅ Prevents division by zero.

✅ Handles incorrect choices gracefully.

Example Run:

-

| Simple Calculator |

-

select your choice of operation from the below options (1 - 4)numbers only:

-

1.)Addition

2.)Substraction

3.)Multiplication

4.)Division

enter your choice from (1- 4) :

a

Invalid Input : you cannot select non - numeric values

select your choice of operation from the options (1 - 4)numbers only:

enter your choice from (1- 4) :

2

Enter your first number:

5

Enter your second number:

3

The Subtraction of 5.0 - 3.0 = 2.0

Conclusion

Your Simple Calculator program is efficient, user-friendly, and error-proof. Let me know if you need further modifications! 🚀😊