Convert roman numerals

[matzahboy]

I made a program to simplify roman numerals (projecteuler.net/index.php?section=problems&id=89]Problem 89 - Project Euler). I think that my method works, but I'm not sure if it is the most efficient method. Is there a way to shorten it and improve the time it takes to run it? Here's my code:

/*
 Converts Roman Numerals
 */
 
 import java.io.*;
import java.util.Scanner;

public class Problem_89 {
    
    
    public static String westernToRoman(int western) {
    	int level=7;
    	String roman = "";
    	while(level>0) {
    		if(western - levelToValue(level)>=0) {
    			roman += String.valueOf(levelToNumeral(level));
    			western -= levelToValue(level);
    		} else {
    			//Check to see if you should use subtraction
    			int subtractorLevel = (int)Math.floor(level/2)*2-1;
    			if(subtractorLevel>0 && western-(levelToValue(level)-levelToValue(subtractorLevel))>=0) {
    				western -= (levelToValue(level)-levelToValue(subtractorLevel));
    				roman = roman + levelToNumeral(subtractorLevel) + levelToNumeral(level);
    			}
    			level--;
    				
    		}
    	}
    	return roman;
    }
    
    public static int romanToWestern(String roman) {
    	
    	int western = 0; //the numerical version
    	char currentChar;
    	char nextChar;
    	
    	int i=0;
    	
    	while(i<roman.length()) {
    		currentChar = roman.charAt(i);
    		if(i<roman.length()-1) {
    			nextChar = roman.charAt(i+1);
    			if(getValue(currentChar)<getValue(nextChar)) {
    				western += (getValue(nextChar) - getValue(currentChar));
    				i+=2;
    			} else {
    				western += getValue(currentChar);
    				i++;
    			}
    		} else {
    			western += getValue(currentChar);
    			i++;
    		}
    	}
    	return western;
    	
    }
    
    private static int getValue(char l) { //Converts the numeral to a number
    	String letter = String.valueOf(l);
    	if(letter.equalsIgnoreCase("I")) return 1;
    	if(letter.equalsIgnoreCase("V")) return 5;
    	if(letter.equalsIgnoreCase("X")) return 10;
    	if(letter.equalsIgnoreCase("L")) return 50;
    	if(letter.equalsIgnoreCase("C")) return 100;
    	if(letter.equalsIgnoreCase("D")) return 500;
    	if(letter.equalsIgnoreCase("M")) return 1000;
    	return 0;
    }
    
    private static char levelToNumeral(int level) {
    	String character;
    	if(level == 1)
    		character = "I";
    	else if(level == 2)
    		character = "V";
    	else if(level == 3)
    		character = "X";
    	else if(level == 4)
    		character = "L";
    	else if(level == 5)
    		character = "C";
    	else if(level == 6)
    		character = "D";
    	else if (level == 7)
    		character = "M";
    	else
    		character = "E";
    	return character.charAt(0);
    }
    
    private static int levelToValue(int level) {
    	if(level == 1)
    		return 1;
    	if(level == 2)
    		return 5;
    	if(level == 3)
    		return 10;
    	if(level == 4)
    		return 50;
    	if(level == 5)
    		return 100;
    	if(level == 6)
    		return 500;
    	if(level == 7)
    		return 1000;
    	//error
    	System.out.println("Error in the getLevel sub. level = " + level);
    	return 1;
    }
    
    public static void main(String[] args) throws FileNotFoundException  {
    	
    	String[] numerals = new String[1000];
    	int charactersBefore=0;
    	int charactersAfter=0;
    	
    	//Read the txt file:
    	File fFile = new File("C:\\roman.txt");
    	Scanner scanner = new Scanner(fFile);
    	int i=0;
    	while ( scanner.hasNextLine() ){
        	numerals[i] = scanner.nextLine();
        	i++;
    	}
    	
    	String simplified;
    	
    	//Calculate "charactersBefore" and then simplify the numerals
    	for (i=0; i<1000; i++) {
    		charactersBefore += numerals[i].length();
    		int western = Problem_89.romanToWestern(numerals[i]);
    		String roman = Problem_89.westernToRoman(western);
    		charactersAfter += roman.length();
    		System.out.println(numerals[i] + " becomes " + western + " which becomes " + roman);
    	}
    	
    	System.out.println("We gained " + (charactersBefore - charactersAfter) + " characters");
    }
}

[Fubarable]

The "best" way is the way that 1) works for you, 2) is reliable and testable, and 3) is understandable to you and to others.

so there are many best and efficient ways to do this. One way is like so:

public enum Roman
{
  M(1000), CM(900), D(500), CD(400), C(100), 
  XC(90), L(50), XL(40), X(10), IX(9), V(5), 
  IV(4), I(1);

  private int number;

  private Roman(int number)
  {
    this.number = number;
  }

  public int getNumber()
  {
    return number;
  }

  public static String toRoman(int arabicInt)
  {
    StringBuilder result = new StringBuilder();
    for (int i = 0; i < values().length; i++)
    {
      int termCount = arabicInt / values()[i].getNumber();
      for (int j = 0; j < termCount; j++)
      {
        result.append(values()[i].toString());
      }
      arabicInt %= values()[i].getNumber();
    }
    return result.toString();
  }

}

public class TestRoman
{
  public static void main(String[] args)
  {
    System.out.println(Roman.toRoman(1975));
    for (int i = 0; i < 400; i++)
    {
      // note empty string "" if int is 0
      System.out.println(Roman.toRoman(i));
    }

  }
}