@Override
  protected java.lang.Object tupleSchemeReadValue(org.apache.thrift.protocol.TProtocol iprot, short fieldID) throws org.apache.thrift.TException {
    _Fields setField = _Fields.findByThriftId(fieldID);
    if (setField != null) {
      switch (setField) {
        case PUT:
          TPut put;
          put = new TPut();
          put.read(iprot);
          return put;
        case DELETE_SINGLE:
          TDelete deleteSingle;
          deleteSingle = new TDelete();
          deleteSingle.read(iprot);
          return deleteSingle;
        default:
          throw new java.lang.IllegalStateException("setField wasn't null, but didn't match any of the case statements!");
      }
    } else {
      throw new org.apache.thrift.protocol.TProtocolException("Couldn't find a field with field id " + fieldID);
    }
  }
Find the _Fields constant that matches name, or null if its not found.
hbase-thrift/src/main/java/org/apache/hadoop/hbase/thrift2/generated/TMutation.java