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

    switch (field) {
    case REGION_ID:
      return isSetRegionId();
    case TABLE_NAME:
      return isSetTableName();
    case START_KEY:
      return isSetStartKey();
    case END_KEY:
      return isSetEndKey();
    case OFFLINE:
      return isSetOffline();
    case SPLIT:
      return isSetSplit();
    case REPLICA_ID:
      return isSetReplicaId();
    }
    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/thrift2/generated/THRegionInfo.java