Getting User Input in Java for a Calculator

General Discussions
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Absolutely! Scanner is easy, BufferedReader is fast, but what if you need security? If you’re working on a command-line calculator and require secure input handling, Console is a great option.

System.console() helps in reading Java user input securely, especially for password-like inputs.

Here’s how you can use it in a calculator:

import java.io.Console;

public class Calculator {
    public static void main(String[] args) {
        Console console = System.console();
        if (console == null) {
            System.out.println("No console available!");
            return;
        }

        double num1 = Double.parseDouble(console.readLine("Enter first number: "));
        char operator = console.readLine("Enter operator (+, -, *, /): ").charAt(0);
        double num2 = Double.parseDouble(console.readLine("Enter second number: "));

        double result = switch (operator) {
            case '+' -> num1 + num2;
            case '-' -> num1 - num2;
            case '*' -> num1 * num2;
            case '/' -> (num2 != 0) ? num1 / num2 : Double.NaN;
            default -> {
                System.out.println("Invalid operator!");
                yield 0;
            }
        };

        console.printf("Result: %.2f%n", result);
    }
}

:small_blue_diamond: Why use Console?

:heavy_check_mark: Best for secure input (e.g., passwords, sensitive data).

:heavy_check_mark: Works well in command-line applications.

:exclamation: Note: It won’t work in some IDEs like Eclipse because they don’t support System.console().

So, which method should you choose?

  • If you need simplicity → Use Scanner.
  • If you need speed for large inputs → Use BufferedReader.
  • If you need security for sensitive inputs → Use Console.

Hope this helps! Let me know if you need any improvements in your calculator! :blush: