1 package org.apache.lucene.analysis.tokenattributes;
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20 import java.io.Serializable;
22 import org.apache.lucene.analysis.TokenStream;
23 import org.apache.lucene.util.AttributeImpl;
25 /** The positionIncrement determines the position of this token
26 * relative to the previous Token in a {@link TokenStream}, used in phrase
29 * <p>The default value is one.
31 * <p>Some common uses for this are:<ul>
33 * <li>Set it to zero to put multiple terms in the same position. This is
34 * useful if, e.g., a word has multiple stems. Searches for phrases
35 * including either stem will match. In this case, all but the first stem's
36 * increment should be set to zero: the increment of the first instance
37 * should be one. Repeating a token with an increment of zero can also be
38 * used to boost the scores of matches on that token.
40 * <li>Set it to values greater than one to inhibit exact phrase matches.
41 * If, for example, one does not want phrases to match across removed stop
42 * words, then one could build a stop word filter that removes stop words and
43 * also sets the increment to the number of stop words removed before each
44 * non-stop word. Then exact phrase queries will only match when the terms
45 * occur with no intervening stop words.
49 public class PositionIncrementAttributeImpl extends AttributeImpl implements PositionIncrementAttribute, Cloneable, Serializable {
50 private int positionIncrement = 1;
52 /** Set the position increment. The default value is one.
54 * @param positionIncrement the distance from the prior term
56 public void setPositionIncrement(int positionIncrement) {
57 if (positionIncrement < 0)
58 throw new IllegalArgumentException
59 ("Increment must be zero or greater: " + positionIncrement);
60 this.positionIncrement = positionIncrement;
63 /** Returns the position increment of this Token.
64 * @see #setPositionIncrement
66 public int getPositionIncrement() {
67 return positionIncrement;
72 this.positionIncrement = 1;
76 public boolean equals(Object other) {
81 if (other instanceof PositionIncrementAttributeImpl) {
82 return positionIncrement == ((PositionIncrementAttributeImpl) other).positionIncrement;
89 public int hashCode() {
90 return positionIncrement;
94 public void copyTo(AttributeImpl target) {
95 PositionIncrementAttribute t = (PositionIncrementAttribute) target;
96 t.setPositionIncrement(positionIncrement);