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1   /*
2    * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
6    * under the terms of the GNU General Public License version 2 only, as
7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
18   * 2 along with this work; if not, write to the Free Software Foundation,
19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
21   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22   * or visit www.oracle.com if you need additional information or have any
23   * questions.
24   */
25  
26  /*
27   * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
28   * (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved
29   *
30   * The original version of this source code and documentation
31   * is copyrighted and owned by Taligent, Inc., a wholly-owned
32   * subsidiary of IBM. These materials are provided under terms
33   * of a License Agreement between Taligent and Sun. This technology
34   * is protected by multiple US and International patents.
35   *
36   * This notice and attribution to Taligent may not be removed.
37   * Taligent is a registered trademark of Taligent, Inc.
38   *
39   */
40  
41  package java.text;
42  
43  
44  /**
45   * This interface defines a protocol for bidirectional iteration over text.
46   * The iterator iterates over a bounded sequence of characters.  Characters
47   * are indexed with values beginning with the value returned by getBeginIndex() and
48   * continuing through the value returned by getEndIndex()-1.
49   * <p>
50   * Iterators maintain a current character index, whose valid range is from
51   * getBeginIndex() to getEndIndex(); the value getEndIndex() is included to allow
52   * handling of zero-length text ranges and for historical reasons.
53   * The current index can be retrieved by calling getIndex() and set directly
54   * by calling setIndex(), first(), and last().
55   * <p>
56   * The methods previous() and next() are used for iteration. They return DONE if
57   * they would move outside the range from getBeginIndex() to getEndIndex() -1,
58   * signaling that the iterator has reached the end of the sequence. DONE is
59   * also returned by other methods to indicate that the current index is
60   * outside this range.
61   *
62   * <P>Examples:<P>
63   *
64   * Traverse the text from start to finish
65   * <pre>{@code
66   * public void traverseForward(CharacterIterator iter) {
67   *     for(char c = iter.first(); c != CharacterIterator.DONE; c = iter.next()) {
68   *         processChar(c);
69   *     }
70   * }
71   * }</pre>
72   *
73   * Traverse the text backwards, from end to start
74   * <pre>{@code
75   * public void traverseBackward(CharacterIterator iter) {
76   *     for(char c = iter.last(); c != CharacterIterator.DONE; c = iter.previous()) {
77   *         processChar(c);
78   *     }
79   * }
80   * }</pre>
81   *
82   * Traverse both forward and backward from a given position in the text.
83   * Calls to notBoundary() in this example represents some
84   * additional stopping criteria.
85   * <pre>{@code
86   * public void traverseOut(CharacterIterator iter, int pos) {
87   *     for (char c = iter.setIndex(pos);
88   *              c != CharacterIterator.DONE && notBoundary(c);
89   *              c = iter.next()) {
90   *     }
91   *     int end = iter.getIndex();
92   *     for (char c = iter.setIndex(pos);
93   *             c != CharacterIterator.DONE && notBoundary(c);
94   *             c = iter.previous()) {
95   *     }
96   *     int start = iter.getIndex();
97   *     processSection(start, end);
98   * }
99   * }</pre>
100  *
101  * @see StringCharacterIterator
102  * @see AttributedCharacterIterator
103  */
104 
105 public interface CharacterIterator extends Cloneable
106 {
107 
108     /**
109      * Constant that is returned when the iterator has reached either the end
110      * or the beginning of the text. The value is '\\uFFFF', the "not a
111      * character" value which should not occur in any valid Unicode string.
112      */
113     public static final char DONE = '\uFFFF';
114 
115     /**
116      * Sets the position to getBeginIndex() and returns the character at that
117      * position.
118      * @return the first character in the text, or DONE if the text is empty
119      * @see #getBeginIndex()
120      */
121     public char first();
122 
123     /**
124      * Sets the position to getEndIndex()-1 (getEndIndex() if the text is empty)
125      * and returns the character at that position.
126      * @return the last character in the text, or DONE if the text is empty
127      * @see #getEndIndex()
128      */
129     public char last();
130 
131     /**
132      * Gets the character at the current position (as returned by getIndex()).
133      * @return the character at the current position or DONE if the current
134      * position is off the end of the text.
135      * @see #getIndex()
136      */
137     public char current();
138 
139     /**
140      * Increments the iterator's index by one and returns the character
141      * at the new index.  If the resulting index is greater or equal
142      * to getEndIndex(), the current index is reset to getEndIndex() and
143      * a value of DONE is returned.
144      * @return the character at the new position or DONE if the new
145      * position is off the end of the text range.
146      */
147     public char next();
148 
149     /**
150      * Decrements the iterator's index by one and returns the character
151      * at the new index. If the current index is getBeginIndex(), the index
152      * remains at getBeginIndex() and a value of DONE is returned.
153      * @return the character at the new position or DONE if the current
154      * position is equal to getBeginIndex().
155      */
156     public char previous();
157 
158     /**
159      * Sets the position to the specified position in the text and returns that
160      * character.
161      * @param position the position within the text.  Valid values range from
162      * getBeginIndex() to getEndIndex().  An IllegalArgumentException is thrown
163      * if an invalid value is supplied.
164      * @return the character at the specified position or DONE if the specified position is equal to getEndIndex()
165      */
166     public char setIndex(int position);
167 
168     /**
169      * Returns the start index of the text.
170      * @return the index at which the text begins.
171      */
172     public int getBeginIndex();
173 
174     /**
175      * Returns the end index of the text.  This index is the index of the first
176      * character following the end of the text.
177      * @return the index after the last character in the text
178      */
179     public int getEndIndex();
180 
181     /**
182      * Returns the current index.
183      * @return the current index.
184      */
185     public int getIndex();
186 
187     /**
188      * Create a copy of this iterator
189      * @return A copy of this
190      */
191     public Object clone();
192 
193 }