public boolean isSet(_Fields field) {
    if (field == null) {
      throw new java.lang.IllegalArgumentException();
    }

    switch (field) {
    case START_KEY:
      return isSetStartKey();
    case END_KEY:
      return isSetEndKey();
    case ID:
      return isSetId();
    case NAME:
      return isSetName();
    case VERSION:
      return isSetVersion();
    case SERVER_NAME:
      return isSetServerName();
    case PORT:
      return isSetPort();
    }
    throw new java.lang.IllegalStateException();
  }
Returns true if field corresponding to fieldID is set (has been assigned a value) and false otherwise
hbase-thrift/src/main/java/org/apache/hadoop/hbase/thrift/generated/TRegionInfo.java