private int literal(char ch){
        switch(ch){
        case 'I' :  
            return 1;
        case 'V' :
            return 5;
        case 'X' :
            return 10;
        case 'L' :
            return 50;
        case 'C' :
            return 100;
        case 'D' :
            return 500;
        case 'M' :
            return 1000;
        default :
            throw new IllegalArgumentException();
        }
    }
Convert a roman number to decimal number
Test cases: smaller number appearing before bigger number unless it is representing one less. 
VL is incorrect since XL should be used to represent 90
chars not used in roman representation is used
http://www.onlineconversion.com/roman_numerals_advanced.htm
src/com/interview/misc/RomanNumberToDecimal.java