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Gryphon

Mon Jun 09, 2008 8:32 pm


String Manipulation - Roman Numerals

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I am currently trying to make a program that converts Roman numerals to arabic numbers(f.y.i. arabic numbers are just normal numbers, 1,2,3 etc.) and visa versa. I think I have a general idea of what is going on but I'm fairly new to many of these string manipulation commands. The problem is that when I enter any input, it is never converted, the program simply outputs whatever the answer variable is initialized as. I think the problem may be how I'm using all the string commands. Any help with this would be greatly appreciated! Thanks! Heres my code so far:


import java.io.*;
public class RomanConverter
{	public static void main(String[] args)
	{	BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in));
		int arabic = 0;
		
		System.out.println("1) Roman Numerals to Arabic numbers, 2) Arabic numbers to Roman Numbers");
		//get(keyboard);
				
		if(get(keyboard).equals("1"))
		{	System.out.println("Enter the Roman numerals you would like to convert to Arabic numbers");
			System.out.println(romanToArabic(get(keyboard)));
		}
		else
		{	System.out.println("Enter the Arabic numbers you would like to convert to Roman numerals");
			arabic = Integer.valueOf(get(keyboard));
			System.out.println(arabicToRoman(arabic));
		}
		
	}
	
	private static String get(BufferedReader br)
	{	try
		{	String inputString=br.readLine();
			return inputString;
		}
		catch(IOException e)
		{	System.out.println("ERROR");
		}
		return null;
	}	
	
	private static int romanToArabic(String s)
	{	int answer = 0;
				
		s.toUpperCase();		
		checkForReplacements(s);
		
		for(int i=0;i>s.length();i++)
		{	if(s.contains("M"))
			{	s.replaceFirst("M"," ");
				s.trim();
				answer += 1000;
			}
			else if(s.contains("D"))
			{	s.replaceFirst("D"," ");
				s.trim();
				answer += 500;
			}
			else if(s.contains("C"))
			{	s.replaceFirst("C"," ");
				s.trim();
				answer += 100;
			}
			else if(s.contains("L"))
			{	s.replaceFirst("L"," ");
				s.trim();
				answer += 50;
			}
			else if(s.contains("X"))
			{	s.replaceFirst("X"," ");
				s.trim();
				answer += 10;
			}
			else if(s.contains("V"))
			{	s.replaceFirst("V"," ");
				s.trim();
				answer += 5;
			}
			else if(s.contains("I"))
			{	s.replaceFirst("I"," ");
				s.trim();
				answer += 1;
			}
		}
		return answer;
	}	
	
	private static void checkForReplacements(String s)
	{	s.replaceAll("CM", "DCCCC");//900
		s.replaceAll("CD", "CCCC");//400
		s.replaceAll("XC", "LXXXX");//90
		s.replaceAll("XL", "XXXX");//40
		s.replaceAll("IX", "VIIII");//9
		s.replaceAll("IV", "IIII");//4
	}
	
	private static String arabicToRoman(int n)
	{	String answer = "";
			
		while(n > 0)
		{	if(n >= 1000)
			{	answer.concat("M");
				n -= 1000;
			}
			else if(n >= 500)
			{	answer.concat("D");
				n -= 500;
			}
			else if(n >= 100)
			{	answer.concat("C");
				n -= 100;
			}
			else if(n >= 50)
			{	answer.concat("L");
				n -= 50;
			}
			else if(n >= 10)
			{	answer.concat("X");
				n -= 10;
			}
			else if(n >= 5)
			{	answer.concat("V");
				n -= 5;
			}
			else if(n >= 1)
			{	answer.concat("I");
				n -= 1;
			}
		}
		replace(answer); //Replaces IIII with IV, and others
		return answer;	
	}
	
	private static void replace(String answer)
	{	answer.replaceAll("DCCCC", "CM");//900
		answer.replaceAll("CCCC", "CD");//400
		answer.replaceAll("LXXXX", "XC");//90
		answer.replaceAll("XXXX", "XL");//40
		answer.replaceAll("VIIII", "IX");//9
		answer.replaceAll("IIII", "IV");//4
	}
}



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OneOffDriveByPoster

Mon Jun 09, 2008 9:04 pm


Re: String Manipulation - Roman Numerals

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The methods in the String class return new strings that are modified the way you would expect.  They are not mutators.  You can check out StringBuffer.