Decrypt String from Alphabet to Integer Mapping

给一个字符串, 解码到数字. 这个题如果split(“#”), 需要判断情况很多, 所以直接扫描

class Solution {
    public String freqAlphabets(String s) {
        StringBuilder sb = new StringBuilder();
        for(int i = 0 ; i < s.length();) {
            if(i < s.length() - 2 && s.charAt(i+2) == '#') {
                sb.append(to(s.substring(i, i+2)));
                i = i + 3;
            }
            else {
                sb.append(to(s.substring(i, i+1)));
                i++;
            }
        }
        
        return sb.toString();
    }
   private char to(String str){
        return (char) ( 96 + Integer.parseInt(str));
   }
}