code: public static String getPropertyRelativeSuffix(String prefix, String str) {
  
          String realPrefix = prefix + ".";
          if (str.startsWith(realPrefix)) {
              return str.substring(realPrefix.length());
          }
          return null;
      }
docs: If str starts with prefix + '.', return the remaining part, otherwise return null.<p>
  
  @param prefix the prefix
  @param str the string to remove the prefix from
  @return str with the prefix removed, or null if it didn't start with prefix + '.'