calculator using scanner class

package afterfeb13;

import java.util.Scanner;

public class calculator {
    static int c = 0;

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter input for a:");
        int a = sc.nextInt();
        System.out.println("Enter input for b:");
        int b = sc.nextInt();

        int d = add(a, b);
        System.out.println("add : " + d);
        int f = sub(a, b);
        System.out.println("sub : " + f);
        int e = multiple(a, b);
        System.out.println("multi : " + e);
        float g = div(a, b);
        System.out.println("div : " + g);
    }

    private static int div(int a, int b) {

        c = a / b;
        return c;

    }

    private static int multiple(int a, int b) {
        c = a * b;
        return c;

    }

    private static int sub(int a, int b) {

        c = a - b;
        return c;

    }

    private static int add(int a, int b) {
        c = a + b;
        return c;

    }

}

Output:

Enter input for a:
1548
Enter input for b:
576
add : 2124
sub : 972
multi : 891648
div : 2.0

Different way calculator:Scanner class as static

package afterfeb13;

import java.util.Scanner;

public class cal {
    static Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        System.out.println("calculatore");
        add();
        sub();
        multiple();
        div();

    }

    private static void div() {
        System.out.println("div Enter input for a:");
        int a = sc.nextInt();
        System.out.println("div Enter input for b:");
        int b = sc.nextInt();

        int c = a / b;
        System.out.println("add of a/b:" + c);

    }

    private static void multiple() {
        System.out.println("multiple Enter input for a:");
        int a = sc.nextInt();
        System.out.println("multiple Enter input for b:");
        int b = sc.nextInt();

        int c = a * b;
        System.out.println("add of a*b:" + c);
    }

    private static void sub() {
        System.out.println("sub Enter input for a:");
        int a = sc.nextInt();
        System.out.println("sub Enter input for b:");
        int b = sc.nextInt();

        int c = a - b;
        System.out.println("sub of a-b:" + c);

    }

    private static void add() {
        System.out.println("add Enter input for a:");
        int a = sc.nextInt();
        System.out.println("add Enter input for b:");
        int b = sc.nextInt();

        int c = a + b;
        System.out.println("add of a+b:" + c);

    }

}

Output:

calculatore
add Enter input for a:
12
add Enter input for b:
23
add of a+b:35
sub Enter input for a:
23
sub Enter input for b:
4
sub of a-b:19
multiple Enter input for a:
23
multiple Enter input for b:
34
add of a*b:782
div Enter input for a:
45
div Enter input for b:
5
add of a/b:9

Reference(TBD):https://www.tpointtech.com/Scanner-class

Java Scanner Class Constructors(TBD)

Java Scanner Class Methods(TBD)

Comments

[Dhanush]

Modern approach using Java 8 features:
lambdas, Streams, Maps, Exception Handling,...

package Programs;

import java.util.*;
import java.util.function.BiFunction;
import java.util.stream.Stream;

public class Calculator {
    private static final Map<Integer, BiFunction<Double, Double, Double>> operations = new LinkedHashMap<>();

    static {
        operations.put(1, (a, b) -> a + b); 
        operations.put(2, (a, b) -> a - b);  
        operations.put(3, (a, b) -> a * b);  
        operations.put(4, (a, b) -> b != 0 ? a / b : Double.NaN);  
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        boolean continueCalc = true;

        while (continueCalc) {
            System.out.println("\nSelect an operation:");
            System.out.println("0. Exit");
            operations.forEach((k, v) -> System.out.println(k + ". " + getOperationName(k)));

            String input = scanner.nextLine();
            int choice;
            try {
                choice = Integer.parseInt(input);
            } catch (NumberFormatException e) {
                System.out.println("Invalid input! Exiting...");
                break;
            }

            if (choice == 0) {
                System.out.println("Exiting the calculator. Goodbye!");
                continueCalc = false;
                continue;
            }

            if (!operations.containsKey(choice)) {
                System.out.println("Invalid choice! Exiting...");
                break;
            }

            System.out.println("Enter two numbers (space-separated): ");
            String[] parts = scanner.nextLine().split(" ");
            double[] numbers = null;
            try {
                numbers = Stream.of(parts)
                                .mapToDouble(Double::parseDouble)
                                .toArray();
            } catch (NumberFormatException e) {
                System.out.println("Invalid number input! Exiting...");
                break;
            }

            if (numbers.length < 2) {
                System.out.println("You must enter two numbers! Exiting...");
                break;
            }

            double result = operations.get(choice).apply(numbers[0], numbers[1]);
            System.out.println("Result: " + result);
        }
        scanner.close();
    }

    private static String getOperationName(int choice) {
        return switch (choice) {
            case 1 -> "Addition";
            case 2 -> "Subtraction";
            case 3 -> "Multiplication";
            case 4 -> "Division";
            default -> "Unknown";
        };
    }
}

You might think this is too much for a calculator. But its preferred where future modifications, extensions, and error handling are important in production.
Output:

[Neelakandan R]

Thanks bro