Función calculadora, parámetros y valor de retorno de Main Aprende programación con ejercicios Java

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;
	}
}