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Java > Open Source Codes > org > apache > lucene > index > TermEnum


1 package org.apache.lucene.index;
2
3 /**
4  * Copyright 2004 The Apache Software Foundation
5  *
6  * Licensed under the Apache License, Version 2.0 (the "License");
7  * you may not use this file except in compliance with the License.
8  * You may obtain a copy of the License at
9  *
10  * http://www.apache.org/licenses/LICENSE-2.0
11  *
12  * Unless required by applicable law or agreed to in writing, software
13  * distributed under the License is distributed on an "AS IS" BASIS,
14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15  * See the License for the specific language governing permissions and
16  * limitations under the License.
17  */
18
19 import java.io.IOException JavaDoc;
20
21 /** Abstract class for enumerating terms.
22
23   <p>Term enumerations are always ordered by Term.compareTo(). Each term in
24   the enumeration is greater than all that precede it. */
25
26 public abstract class TermEnum {
27   /** Increments the enumeration to the next element. True if one exists.*/
28   public abstract boolean next() throws IOException JavaDoc;
29
30   /** Returns the current Term in the enumeration.*/
31   public abstract Term term();
32
33   /** Returns the docFreq of the current Term in the enumeration.*/
34   public abstract int docFreq();
35
36   /** Closes the enumeration to further activity, freeing resources. */
37   public abstract void close() throws IOException JavaDoc;
38   
39 // Term Vector support
40
41   /** Skips terms to the first beyond the current whose value is
42    * greater or equal to <i>target</i>. <p>Returns true iff there is such
43    * an entry. <p>Behaves as if written: <pre>
44    * public boolean skipTo(Term target) {
45    * do {
46    * if (!next())
47    * return false;
48    * } while (target > term());
49    * return true;
50    * }
51    * </pre>
52    * Some implementations are considerably more efficient than that.
53    */
54   public boolean skipTo(Term target) throws IOException JavaDoc {
55      do {
56         if (!next())
57             return false;
58      } while (target.compareTo(term()) > 0);
59      return true;
60   }
61 }
62
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