public String getStringValue() {
    if (values == null) {
      return null;
    }
    if (stringCache == null) {
      stringCache = new String(this.values, STRING_CHARSET);
    }
    return stringCache;
  }
Get length of values. Returns -1 if values is null.

@return length
iotdb-api/pipe-api/src/main/java/org/apache/iotdb/pipe/api/type/Binary.java