content: package org.apache.lucene.search.grouping;
  
  /*
   * 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.
   */
  
  import org.apache.lucene.search.Collector;
  import org.apache.lucene.search.Scorer;
  import org.apache.lucene.util.BytesRef;
  
  import java.io.IOException;
  import java.util.Collection;
  
  /**
   * A collector that collects all groups that match the
   * query. Only the group value is collected, and the order
   * is undefined.  This collector does not determine
   * the most relevant document of a group.
   *
   * <p/>
   * This is an abstract version. Concrete implementations define
   * what a group actually is and how it is internally collected.
   *
   * @lucene.experimental
   */
  public abstract class AbstractAllGroupsCollector<GROUP_VALUE_TYPE> extends Collector {
  
    /**
     * Returns the total number of groups for the executed search.
     * This is a convenience method. The following code snippet has the same effect: <pre>getGroups().size()</pre>
     *
     * @return The total number of groups for the executed search
     */
    public int getGroupCount() {
      return getGroups().size();
    }
  
    /**
     * Returns the group values
     * <p/>
     * This is an unordered collections of group values. For each group that matched the query there is a {@link BytesRef}
     * representing a group value.
     *
     * @return the group values
     */
    public abstract Collection<GROUP_VALUE_TYPE> getGroups();
  
    // Empty not necessary
    public void setScorer(Scorer scorer) throws IOException {}
  
    public boolean acceptsDocsOutOfOrder() {
      return true;
    }
  }