Roman to Arabic numbers

RomanToDecimal.java

import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Scanner;


class RomanToDecimal {
    private static Scanner input = new Scanner(System.in);
    private static List<Character> romanChars = new LinkedList<>();
    private static Map<Character, Integer> romanCharsVals = new HashMap<>();

    public static void main(String[] args) {
        addValues();
        System.out.print("\nInsert a roman number: ");

        try {
            String in = input.nextLine().trim().toUpperCase();
            int decimal = convertToDecimal(in);
            System.out.println(in + " in decimal is " + decimal);
        } catch (Exception e) {
            System.err.println(e.getMessage());
        }
    }

    // Converts from Roman to Arabic numbers
    private static int convertToDecimal(String roman) throws Exception {
        int result = 0;
        int currentTotal = 0;

        if (roman.length() == 0) {
            throw new Exception("Input is empty");
        }

        for (int i = 0; i < roman.length(); i++) {

            if (!romanChars.contains(roman.charAt(i))) {
                throw new Exception("Invalid character entered");
            }

            if (i < roman.length() - 1) {
                if (romanChars.indexOf(roman.charAt(i)) < romanChars.indexOf(roman.charAt(i + 1))) {
                    currentTotal += romanCharsVals.get(roman.charAt(i + 1)) - romanCharsVals.get(roman.charAt(i));
                    i++;
                } else {
                    currentTotal += romanCharsVals.get(roman.charAt(i));
                }
            } else {
                currentTotal += romanCharsVals.get(roman.charAt(i));
            }
            
            result += currentTotal;
            currentTotal = 0;
        }

        return result;
    }

    // Adds values to list and map
    private static void addValues() {
        romanChars.add('I');
        romanChars.add('V');
        romanChars.add('X');
        romanChars.add('L');
        romanChars.add('C');
        romanChars.add('D');
        romanChars.add('M');
        
        romanCharsVals.put(romanChars.get(0), 1);
        romanCharsVals.put(romanChars.get(1), 5);
        romanCharsVals.put(romanChars.get(2), 10);
        romanCharsVals.put(romanChars.get(3), 50);
        romanCharsVals.put(romanChars.get(4), 100);
        romanCharsVals.put(romanChars.get(5), 500);
        romanCharsVals.put(romanChars.get(6), 1000);
    }

}