01 package gate.creole.annic.apache.lucene.index;
02
03 /**
04 * Copyright 2004 The Apache Software Foundation
05 *
06 * Licensed under the Apache License, Version 2.0 (the "License");
07 * you may not use this file except in compliance with the License.
08 * You may obtain a copy of the License at
09 *
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;
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;
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;
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 {
55 do {
56 if (!next())
57 return false;
58 } while (target.compareTo(term()) > 0);
59 return true;
60 }
61 }
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