@org.apache.thrift.annotation.Nullable
    public static _Fields findByThriftId(int fieldId) {
      switch(fieldId) {
        case 1: // START_KEY
          return START_KEY;
        case 2: // END_KEY
          return END_KEY;
        case 3: // ID
          return ID;
        case 4: // NAME
          return NAME;
        case 5: // VERSION
          return VERSION;
        case 6: // SERVER_NAME
          return SERVER_NAME;
        case 7: // PORT
          return PORT;
        default:
          return null;
      }
    }
Find the _Fields constant that matches fieldId, or null if its not found.
hbase-thrift/src/main/java/org/apache/hadoop/hbase/thrift/generated/TRegionInfo.java