Java Code Example: simple calculator

The simple calculator expects user input for the arithmetic operation, and for the two numbers that are to be calculated together. Depending on the arithmetic symbol, a switch statement is used to decide which arithmetic operation is to be performed.

import java.util.Scanner;

public class SimpleCalculator {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        double firstNumber, secondNumber, result = 0.0;
        char arithmeticOperation;
    
        System.out.print("Please enter an arithmetic operation (+, -, *, /): ");
        arithmeticOperation = scan.next().charAt(0);
        System.out.print("Please enter your first number: ");
        firstNumber = scan.nextInt();
        System.out.print("Please enter your second number: ");
        secondNumber = scan.nextInt();
    
        switch (arithmeticOperation) {
            case '+' :
                result = firstNumber + secondNumber; 
                break;
            case '-' :
                result = firstNumber - secondNumber;
                break;
            case '*' : 
                result = firstNumber * secondNumber;
                break;
            case '/' :
                result = firstNumber / secondNumber;
                break;
            default:
                System.out.print("Unknown arithmetic symbol");
        }

        System.out.print(firstNumber + " " + arithmeticOperation + " " + secondNumber + " = " + result);
    }
}

Output

Please enter an arithmetic operation (+, -, *, /): -
Please enter your first number: 34
Please enter your second number: 23
34.0 - 23.0 = 11.0

Code Explanation

Here’s a detailed explanation of the code:

1. We import the Scanner class to read input from the user.

import java.util.Scanner;

2. We define the SimpleCalculator class with a main method.

public class SimpleCalculator {
    public static void main(String[] args) {

3. We create a new Scanner object to read input from the user.

Scanner scan = new Scanner(System.in);

4. We declare three double variables to hold the first number, second number, and result of the calculation.

double firstNumber, secondNumber, result = 0.0;

5. We declare a char variable to hold the arithmetic operation entered by the user.

char arithmeticOperation;

6. We prompt the user to enter an arithmetic operation and read it using the Scanner object.

System.out.print("Please enter an arithmetic operation (+, -, *, /): ");
arithmeticOperation = scan.next().charAt(0);

7. We prompt the user to enter the first number and read it using the Scanner object.

System.out.print("Please enter your first number: ");
firstNumber = scan.nextInt();

8. We prompt the user to enter the second number and read it using the Scanner object.

System.out.print("Please enter your second number: ");
secondNumber = scan.nextInt();

9. We use a switch statement to determine which arithmetic operation was selected and perform the appropriate calculation.

 switch (arithmeticOperation) {
            case '+' :
                result = firstNumber + secondNumber; 
                break;
            case '-' :
                result = firstNumber - secondNumber;
                break;
            case '*' : 
                result = firstNumber * secondNumber;
                break;
            case '/' :
                result = firstNumber / secondNumber;
                break;
            default:
                System.out.print("Unknown arithmetic symbol");
}

10. We display the result of the calculation using System.out.print.

System.out.print(firstNumber + " " + arithmeticOperation + " " + secondNumber + " = " + result);