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Lucene example source code file (DocIdSet.java)

This example Lucene source code file (DocIdSet.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

docidset, docidsetiterator, docidsetiterator, empty_docidset, io, ioexception, ioexception, no_more_docs, no_more_docs, override, override

The Lucene DocIdSet.java source code

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;

/**
 * A DocIdSet contains a set of doc ids. Implementing classes must
 * only implement {@link #iterator} to provide access to the set. 
 */
public abstract class DocIdSet {

  /** An empty {@code DocIdSet} instance for easy use, e.g. in Filters that hit no documents. */
  public static final DocIdSet EMPTY_DOCIDSET = new DocIdSet() {
    
    private final DocIdSetIterator iterator = new DocIdSetIterator() {
      @Override
      public int advance(int target) throws IOException { return NO_MORE_DOCS; }
      @Override
      public int docID() { return NO_MORE_DOCS; }
      @Override
      public int nextDoc() throws IOException { return NO_MORE_DOCS; }
    };
    
    @Override
    public DocIdSetIterator iterator() {
      return iterator;
    }
    
    @Override
    public boolean isCacheable() {
      return true;
    }
  };
    
  /** Provides a {@link DocIdSetIterator} to access the set.
   * This implementation can return <code>null or
   * <code>{@linkplain #EMPTY_DOCIDSET}.iterator() if there
   * are no docs that match. */
  public abstract DocIdSetIterator iterator() throws IOException;

  /**
   * This method is a hint for {@link CachingWrapperFilter}, if this <code>DocIdSet
   * should be cached without copying it into a BitSet. The default is to return
   * <code>false. If you have an own DocIdSet implementation
   * that does its iteration very effective and fast without doing disk I/O,
   * override this method and return <code>true.
   */
  public boolean isCacheable() {
    return false;
  }
}

Other Lucene examples (source code examples)

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