IntegertoRoman&RomantoInteger

 1 public class Solution {
 2     /**
 3      * @param s Roman representation
 4      * @return an integer
 5      */
 6     public int romanToInt(String s) {
 7         if(s.length() <1) return 0;
 8         int value = 0;
 9         int pValue = getRomanValue(s.charAt(0)); // the value of previous character
10         
11         for (int i = 1; i ) {
12             int cValue = getRomanValue(s.charAt(i));
13             if (pValue >= cValue) { 
14                 value += pValue;
15             } else {
16                 value -= pValue;
17             }
18             pValue = cValue;
19         }
20         value += pValue; // we always add the last value to value. No exception.
21         return value;
22         
23     }
24     public int getRomanValue(char c) {
25         switch(c) {
26             case 'I': return 1; 
27             case 'V': return 5;
28             case 'X': return 10;
29             case 'L': return 50;
30             case 'C': return 100;
31             case 'D': return 500;
32             case 'M': return 1000;
33             default: return 0;
34         }
35     }
36 }