content: package org.apache.lucene.search;
  
  /**
   * 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 java.io.IOException;
  
  /**
   * Abstract decorator class of a DocIdSetIterator
   * implementation that provides on-demand filter/validation
   * mechanism on an underlying DocIdSetIterator.  See {@link
   * FilteredDocIdSet}.
   */
  public abstract class FilteredDocIdSetIterator extends DocIdSetIterator {
    protected DocIdSetIterator _innerIter;
    private int doc;
  	
    /**
     * Constructor.
     * @param innerIter Underlying DocIdSetIterator.
     */
    public FilteredDocIdSetIterator(DocIdSetIterator innerIter) {
      if (innerIter == null) {
        throw new IllegalArgumentException("null iterator");
      }
      _innerIter = innerIter;
      doc = -1;
    }
  	
    /**
     * Validation method to determine whether a docid should be in the result set.
     * @param doc docid to be tested
     * @return true if input docid should be in the result set, false otherwise.
     * @see #FilteredDocIdSetIterator(DocIdSetIterator)
     */
    abstract protected boolean match(int doc) throws IOException;
  	
    @Override
    public int docID() {
      return doc;
    }
    
    @Override
    public int nextDoc() throws IOException {
      while ((doc = _innerIter.nextDoc()) != NO_MORE_DOCS) {
        if (match(doc)) {
          return doc;
        }
      }
      return doc;
    }
    
    @Override
    public int advance(int target) throws IOException {
      doc = _innerIter.advance(target);
      if (doc != NO_MORE_DOCS) {
        if (match(doc)) {
          return doc;
        } else {
          while ((doc = _innerIter.nextDoc()) != NO_MORE_DOCS) {
            if (match(doc)) {
              return doc;
            }
          }
          return doc;
        }
      }
      return doc;
    }
    
  }
  