@Override
      protected boolean inRange(String value, Object lower, Object upper) {
        float fvalue = Float.parseFloat(value);
        if (lower != null && fvalue < (Float)lower) {
          return false;
        }
        if (upper != null && fvalue > (Float)upper) {
          return false;
        }
        return true;
      }
validate value for a ConfVar, return non-null string for fail message
common/src/java/org/apache/hadoop/hive/conf/Validator.java