Arithmetic Table

/**************************************************************************************************
 *  Program Name:     Programming Project 4.6: Arithmetic Table
 *  Author:           Terry Weiss
 *  Date Written:     September 25, 2015
 *  Course/Section:   CSC 111-003W
 *  Program Description:
 *     Design and implement an application that produces an arithmetic table, showing the
 *  results of a user-specified operation on the integers 1 through a user-defined maximum.
 **************************************************************************************************/

import java.util.Scanner;


public class ArithmeticTable
{
    public static String makeTable( String operator, int highestFactor )
    {
        int column, row, value;
        String table = "";

        // Print the header row
        table += operator + "\t";
        for (column = 1; column <= highestFactor; column++)
        {
            table += String.format("%3d\t", column);
        }
        table += "\n";

        // Print table
        for (row = 1; row <= highestFactor; row++ )
        {
            table += String.format("%2d|\t", row);   // Display row number

            for (column = 1; column <= highestFactor; column++)
            {
                if (operator.equals(" x"))
                {
                    value = row * column;
                }
                else if (operator.equals(" +"))
                {
                    value = row + column;
                }
                else if (operator.equals(" -"))
                {
                    value = row - column;
                }
                else // unsupported operation
                {
                    value = 0;
                }

                table += String.format("%3d\t", value);
            }

            table += "\n";
        }

        return table;
    }



    public static void main( String[] args )
    {
        String[] operatorList = { "", " +", " -", " x" };
        String[] operation = { "", "add", "subtract", "multiply" };
        final int MIN_FACTOR = 1, MAX_FACTOR = 20;

        String number, choice;
        int highestFactor, menuChoice;
        Scanner user_input = new Scanner(System.in);

        do
        {
            System.out.print(
                      "\t1. Addition\n"
                    + "\t2. Subtraction\n"
                    + "\t3. Multiplication\n"
                    + "Please enter which table you'd like to make: ");
            choice = user_input.next();

            try {
                menuChoice = Integer.parseInt(choice);
            } catch (NumberFormatException e) {
                System.out.println("That's not a number!");
                menuChoice = -1;
            }
        } while (menuChoice < 1 || menuChoice > 3);

        do
        {
            System.out.print("Please enter how high you'd like to " + operation[menuChoice]
                    + " (up to 20):  ");
            number = user_input.next();

            try {
                highestFactor = Integer.parseInt(number);
            } catch (NumberFormatException e) {
                System.out.print("That's not a number! ");
                highestFactor = -1;
            }
        } while (highestFactor < MIN_FACTOR || highestFactor > MAX_FACTOR);

        System.out.println(makeTable(operatorList[menuChoice], highestFactor));
    }
}