public static <T extends OperatorDesc> Operator<T> get(T conf,
    Operator<? extends OperatorDesc> oplist0, Operator<? extends OperatorDesc>... oplist) {
    Operator<T> ret = get(oplist0.getCompilationOpContext(), (Class<T>) conf.getClass());
    ret.setConf(conf);
    makeChild(ret, oplist0);
    makeChild(ret, oplist);
    return (ret);
  }
Returns an operator given the conf and a list of children operators.
ql/src/java/org/apache/hadoop/hive/ql/exec/OperatorFactory.java