content: /**
   * Copyright 2010 The Apache Software Foundation
   *
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.alibaba.wasp.plan.operator;
  
  import com.alibaba.wasp.util.Node;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * Basic Operator.
   *
   */
  public abstract class Operator implements Node {
  
    private List<Operator> childOperators = new ArrayList<Operator>();
  
    public void addChild(Operator op) {
      childOperators.add(op);
    }
  
    public void setChildOperators(List<Operator> childOperators) {
      this.childOperators = childOperators;
    }
  
    public List<Operator> getChildOperators() {
      return childOperators;
    }
  
    abstract public Object forward(Object row);
  
    @Override
    public List<? extends Node> getChildren() {
      return childOperators;
    }
  
  }
  