Calculator, params and return value of Main - Practice Exercises Java

Lesson 5:

Functions

Exercise 5.32:

Calculator, params and return value of Main

Objetive:

Create a program to calculate a sum, subtraction, product or division, analyzing the command line parameters:

calc 5 + 379

(Parameters must be a number, a sign, and another number; allowed signs are + - * x / )

This version must return the following error codes:
1 if the number of parameters is not 3
2 if the second parameter is not an accepted sign
3 if the first or third parameter is not a valid number
0 otherwise

public class Main
{
	public static int main(String[] args)
	{
		if (args.length != 3)
		{
			System.out.println("Error!");
			System.out.println("Usage: number1 operand number2");
			System.out.println("Where operand can be + - / * x ·");
			return 1;
		}

		try
		{
			int number1 = Integer.parseInt(args[0]);
			int number2 = Integer.parseInt(args[2]);

			switch (args[1])
			{
				case "+":
				{
						System.out.println(number1 + number2);
						break;
				}

				case "-":
				{
						System.out.println(number1 - number2);
						break;
				}

				case "/":
				{
						System.out.println(number1 / number2);
						break;
				}

				case "*":
				case "x":
				case "·":
				{
						System.out.println(number1 * number2);
						break;
				}

				default:
				{
						System.out.println("Error!");
						System.out.println("Operand must be + - / * x or ·");
						return 2;
						break;
				}
			}
		}

		catch (RuntimeException e)
		{
			System.out.println("Error!");
			System.out.println("Not a valid number");
			return 3;
		}

		return 0;
	}
}