Java final

java final

/**
Convert to Roman Numerals
Author: Chrissy LeMaire
Cohort: M0706
FINAL PROJECT
Last Changed: March 10, 2007.
*/

import java.*;
import java.util.*;
import java.lang.Math.*;


public class convertRoman
{
	public static void main(String args[])
	{
		String romanInput;
		Integer runningTotal = 0,index,nextNum,currNum;
		Character tokenizedInput;

		/* We will use a hashmap to store the Roman Numerals and their buddies.
		   http://java.sun.com/j2se/1.4.2/docs/api/java/util/HashMap.html
		   Hashmaps are like VB's Dictionary object. They map a key to a value.
		   In this case, "C" would be a key and 100 would be the value. */

		HashMap<Character, Integer> map = new HashMap<Character, Integer>();
			//  ^Stronger typing prevents compile warning: convertRoman.java uses unchecked or unsafe operations.
			//	More Info @ http://groups.google.com/group/uw.cs.cs241/msg/2fa36118400f83d1
		map.put('I',1);
		map.put('V',5);
		map.put('X',10);
		map.put('L',50);
		map.put('C',100);
		map.put('D',500);
		map.put('M',1000);

		Scanner keyboard = new Scanner(System.in);

		System.out.println("Type in number to convert:");
		System.out.println();
		romanInput = keyboard.nextLine().toUpperCase(); // because Java is case-sensitive
		romanInput = romanInput.trim(); // just in case


		for (index = 0; index < romanInput.length(); index++)
			{
				/* Below we will check to see if there are more than 4 characters of the same type in a row.*/
				if (index+3 < romanInput.length()) 				// In order to not throw an exeption
					if (
						romanInput.charAt(index) == romanInput.charAt(index+1) &&
						romanInput.charAt(index) == romanInput.charAt(index+2) &&
						romanInput.charAt(index) == romanInput.charAt(index+3))
					{
					System.out.println("Warning: As a general guideline, you may want to consider not using the same character four times in a row.");
					System.out.println("");
					}

				/*  stringTokenizer is good for full words, but not characters. We will use a charAt index instead.
					More info here: http://www.ling.ohio-state.edu/~kcohen/javaStringHandling.html */
				tokenizedInput = romanInput.charAt(index);

				/* If the input contains anything other than IVXLCDM, Reject */
				if (map.containsKey(tokenizedInput) == false)
					{
					System.out.println("Foo, that aint no roman numeral.");
					System.exit(0);
					}

				/* Alright, Let's Start */
				currNum = map.get(tokenizedInput); //Convert tokenziedInput (such as "I") to its numerical value ("1")

				/*
				We need to follow a few rules here:
				1. Subtract only powers of ten, such as I, X, or C. Writing VL for 45 is not allowed: write XLV instead.
				2. Subtract only a single letter from a single numeral. Write VIII for 8, not IIX; 19 is XIX, not IXX.
				3. Don't subtract a letter from another letter more than ten times greater. This means that you can only
				  subtract I from V or X, and X from L or C, so MIM is illegal.

				In this code, we will "look ahead" to the next roman numeral to determine if we must subtract or add.
				We will look ahead by using index+1, but only if index+1 isn't too big of a number.
				*/

				if (index+1 < romanInput.length()) // To make sure we try to look past the last numeral.
					{
					nextNum = map.get(romanInput.charAt(index+1)); //Get the next numeral

						if(currNum >= nextNum) // if its more than or equal to, add it.
							runningTotal = runningTotal + currNum;
						else //otherwise, subtract it. But only if it follows the rules.

							if  ( ((Math.log(index)/Math.log(10))%1 == 0 && index>1) || (nextNum/10>currNum) ) //this addresses rule #1 and #3

								{
								System.out.println("Your roman numeral is not valid.");
								System.exit(0);
								}
							else
								{
								runningTotal = runningTotal + (nextNum-currNum);
								index++; // This, by nature, takes care of rule #2 -- we never parse more than 2 at a time.
								}
					}
				else
				// It's the last character. It can only be added.
				runningTotal = runningTotal + currNum;

			}

				System.out.println(runningTotal);
	}
}