lucene/core/src/java/org/apache/lucene/analysis/tokenattributes/PositionIncrementAttribute.java

/*
 * 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.lucene.analysis.tokenattributes;


import org.apache.lucene.util.Attribute;

/** Determines the position of this token
 * relative to the previous Token in a TokenStream, used in phrase
 * searching.
 *
 * <p>The default value is one.
 *
 * <p>Some common uses for this are:<ul>
 *
 * <li>Set it to zero to put multiple terms in the same position.  This is
 * useful if, e.g., a word has multiple stems.  Searches for phrases
 * including either stem will match.  In this case, all but the first stem's
 * increment should be set to zero: the increment of the first instance
 * should be one.  Repeating a token with an increment of zero can also be
 * used to boost the scores of matches on that token.
 *
 * <li>Set it to values greater than one to inhibit exact phrase matches.
 * If, for example, one does not want phrases to match across removed stop
 * words, then one could build a stop word filter that removes stop words and
 * also sets the increment to the number of stop words removed before each
 * non-stop word.  Then exact phrase queries will only match when the terms
 * occur with no intervening stop words.
 *
 * </ul>
 * 
 * @see org.apache.lucene.index.PostingsEnum
 */
public interface PositionIncrementAttribute extends Attribute {
  /** Set the position increment. The default value is one.
   *
   * @param positionIncrement the distance from the prior term
   * @throws IllegalArgumentException if <code>positionIncrement</code> 
   *         is negative.
   * @see #getPositionIncrement()
   */
  public void setPositionIncrement(int positionIncrement);

  /** Returns the position increment of this Token.
   * @see #setPositionIncrement(int)
   */
  public int getPositionIncrement();
}