content: /*
   * 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 org.apache.calcite.plan;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * MulticastRelOptListener implements the {@link RelOptListener} interface by
   * forwarding events on to a collection of other listeners.
   */
  public class MulticastRelOptListener implements RelOptListener {
    //~ Instance fields --------------------------------------------------------
  
    private final List<RelOptListener> listeners;
  
    //~ Constructors -----------------------------------------------------------
  
    /**
     * Creates a new empty multicast listener.
     */
    public MulticastRelOptListener() {
      listeners = new ArrayList<>();
    }
  
    //~ Methods ----------------------------------------------------------------
  
    /**
     * Adds a listener which will receive multicast events.
     *
     * @param listener listener to add
     */
    public void addListener(RelOptListener listener) {
      listeners.add(listener);
    }
  
    // implement RelOptListener
    @Override public void relEquivalenceFound(RelEquivalenceEvent event) {
      for (RelOptListener listener : listeners) {
        listener.relEquivalenceFound(event);
      }
    }
  
    // implement RelOptListener
    @Override public void ruleAttempted(RuleAttemptedEvent event) {
      for (RelOptListener listener : listeners) {
        listener.ruleAttempted(event);
      }
    }
  
    // implement RelOptListener
    @Override public void ruleProductionSucceeded(RuleProductionEvent event) {
      for (RelOptListener listener : listeners) {
        listener.ruleProductionSucceeded(event);
      }
    }
  
    // implement RelOptListener
    @Override public void relChosen(RelChosenEvent event) {
      for (RelOptListener listener : listeners) {
        listener.relChosen(event);
      }
    }
  
    // implement RelOptListener
    @Override public void relDiscarded(RelDiscardedEvent event) {
      for (RelOptListener listener : listeners) {
        listener.relDiscarded(event);
      }
    }
  }
  