Programming Merit Badge 5b - Java - (C) 2017 Wilson Gramer

/*
 * Main.java
 * Programming Merit Badge - 5b
 *
 * Copyright (C) 2017 Wilson Gramer.
 * All rights reserved.
 */
package co.neef.java.bsa.prgmb.five.b;

import static java.lang.System.exit;

public class Main {

    /**
     * Usage: 'java Main [first number] [operator] [second number] Operators
     * include '+', '-', 'x', and '/'; for ADDITION, SUBTRACTION,
     * MULTIPLICATION, and DIVISION.
     *
     * @param args
     */
    public static void main(String[] args) {
        try { //ADDDED AFTER DEBUG
            switch (args[1]) {
                case "+":
                    System.out.println(args[0] + " " + args[1] + " " + args[2] + " = " + add(args[0], args[2]));
                    break;
                case "-":
                    System.out.println(args[0] + " " + args[1] + " " + args[2] + " = " + sub(args[0], args[2]));
                    break;
                case "x":
                    System.out.println(args[0] + " " + args[1] + " " + args[2] + " = " + mul(args[0], args[2]));
                    break;
                case "/":
                    System.out.println(args[0] + " " + args[1] + " " + args[2] + " = " + div(args[0], args[2]));
                    break;
                default:
                    System.err.println("Usage: 'java Main [first number] [operator] [second number]");
                    System.err.println("Operators include '+', '-', 'x', and '/'; for ADDITION, SUBTRACTION, MULTIPLICATION, and DIVISION.");
            }
        } catch (java.lang.IndexOutOfBoundsException err) { //ADDDED AFTER DEBUG
            System.err.println("Please provide all arguments."); //ADDDED AFTER DEBUG
            System.err.println(); //ADDDED AFTER DEBUG
            System.err.println("Usage: 'java Main [first number] [operator] [second number]"); //ADDDED AFTER DEBUG
            System.err.println("Operators include '+', '-', '*', and '/'; for ADDITION, SUBTRACTION, MULTIPLICATION, and DIVISION."); //ADDDED AFTER DEBUG
            System.err.println(); //ADDDED AFTER DEBUG
            exit(0); //ADDDED AFTER DEBUG
        } //ADDDED AFTER DEBUG
    }

    private static String add(String n1, String n2) {
        String answer = "ERROR";

        answer = n1 + n2;

        return answer;
    }

    private static String sub(String n1, String n2) {
        String answer = "ERROR";

        answer = n1.replace(n2, "");

        return answer;
    }

    private static String mul(String n1, String n2) {
        String answer = "ERROR";

        Integer j = Integer.parseInt(n2) / 2;

        for (int i = 0; i < j; i++) n1 = n1 + n1;
        answer = n1;

        return answer;
    }

    private static String div(String n1, String n2) {
        String answer = "ERROR";

        String[] answerArr = n1.split("(?<=\\G.{" + Integer.parseInt(n2) + "})");

        StringBuilder strBuilder = new StringBuilder();
        for (int i = 0; i < answerArr.length; i++) {
            strBuilder.append(answerArr[i] + " ");
        }
        answer = strBuilder.toString();

        return answer;
    }
}