1 /*
2 * Copyright (c) 2000, 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 package java.lang;
27
28 import java.util.NoSuchElementException;
29 import java.util.PrimitiveIterator;
30 import java.util.Spliterator;
31 import java.util.Spliterators;
32 import java.util.function.IntConsumer;
33 import java.util.stream.IntStream;
34 import java.util.stream.StreamSupport;
35
36 /**
37 * A <tt>CharSequence</tt> is a readable sequence of <code>char</code> values. This
38 * interface provides uniform, read-only access to many different kinds of
39 * <code>char</code> sequences.
40 * A <code>char</code> value represents a character in the <i>Basic
41 * Multilingual Plane (BMP)</i> or a surrogate. Refer to <a
42 * href="Character.html#unicode">Unicode Character Representation</a> for details.
43 *
44 * <p> This interface does not refine the general contracts of the {@link
45 * java.lang.Object#equals(java.lang.Object) equals} and {@link
46 * java.lang.Object#hashCode() hashCode} methods. The result of comparing two
47 * objects that implement <tt>CharSequence</tt> is therefore, in general,
48 * undefined. Each object may be implemented by a different class, and there
49 * is no guarantee that each class will be capable of testing its instances
50 * for equality with those of the other. It is therefore inappropriate to use
51 * arbitrary <tt>CharSequence</tt> instances as elements in a set or as keys in
52 * a map. </p>
53 *
54 * @author Mike McCloskey
55 * @since 1.4
56 * @spec JSR-51
57 */
58
59 public interface CharSequence {
60
61 /**
62 * Returns the length of this character sequence. The length is the number
63 * of 16-bit <code>char</code>s in the sequence.</p>
64 *
65 * @return the number of <code>char</code>s in this sequence
66 */
67 int length();
68
69 /**
70 * Returns the <code>char</code> value at the specified index. An index ranges from zero
71 * to <tt>length() - 1</tt>. The first <code>char</code> value of the sequence is at
72 * index zero, the next at index one, and so on, as for array
73 * indexing. </p>
74 *
75 * <p>If the <code>char</code> value specified by the index is a
76 * <a href="{@docRoot}/java/lang/Character.html#unicode">surrogate</a>, the surrogate
77 * value is returned.
78 *
79 * @param index the index of the <code>char</code> value to be returned
80 *
81 * @return the specified <code>char</code> value
82 *
83 * @throws IndexOutOfBoundsException
84 * if the <tt>index</tt> argument is negative or not less than
85 * <tt>length()</tt>
86 */
87 char charAt(int index);
88
89 /**
90 * Returns a new <code>CharSequence</code> that is a subsequence of this sequence.
91 * The subsequence starts with the <code>char</code> value at the specified index and
92 * ends with the <code>char</code> value at index <tt>end - 1</tt>. The length
93 * (in <code>char</code>s) of the
94 * returned sequence is <tt>end - start</tt>, so if <tt>start == end</tt>
95 * then an empty sequence is returned. </p>
96 *
97 * @param start the start index, inclusive
98 * @param end the end index, exclusive
99 *
100 * @return the specified subsequence
101 *
102 * @throws IndexOutOfBoundsException
103 * if <tt>start</tt> or <tt>end</tt> are negative,
104 * if <tt>end</tt> is greater than <tt>length()</tt>,
105 * or if <tt>start</tt> is greater than <tt>end</tt>
106 */
107 CharSequence subSequence(int start, int end);
108
109 /**
110 * Returns a string containing the characters in this sequence in the same
111 * order as this sequence. The length of the string will be the length of
112 * this sequence. </p>
113 *
114 * @return a string consisting of exactly this sequence of characters
115 */
116 public String toString();
117
118 /**
119 * Returns a stream of {@code int} zero-extending the {@code char} values
120 * from this sequence. Any char which maps to a <a
121 * href="{@docRoot}/java/lang/Character.html#unicode">surrogate code
122 * point</a> is passed through uninterpreted.
123 *
124 * <p>If the sequence is mutated while the stream is being read, the
125 * result is undefined.
126 *
127 * @return an IntStream of char values from this sequence
128 * @since 1.8
129 */
130 public default IntStream chars() {
131 class CharIterator implements PrimitiveIterator.OfInt {
132 int cur = 0;
133
134 public boolean hasNext() {
135 return cur < length();
136 }
137
138 public int nextInt() {
139 if (hasNext()) {
140 return charAt(cur++);
141 } else {
142 throw new NoSuchElementException();
143 }
144 }
145
146 @Override
147 public void forEachRemaining(IntConsumer block) {
148 for (; cur < length(); cur++) {
149 block.accept(charAt(cur));
150 }
151 }
152 }
153
154 return StreamSupport.intStream(() ->
155 Spliterators.spliterator(
156 new CharIterator(),
157 length(),
158 Spliterator.ORDERED),
159 Spliterator.SUBSIZED | Spliterator.SIZED | Spliterator.ORDERED);
160 }
161
162 /**
163 * Returns a stream of code point values from this sequence. Any surrogate
164 * pairs encountered in the sequence are combined as if by {@linkplain
165 * Character#toCodePoint Character.toCodePoint} and the result is passed
166 * to the stream. Any other code units, including ordinary BMP characters,
167 * unpaired surrogates, and undefined code units, are zero-extended to
168 * {@code int} values which are then passed to the stream.
169 *
170 * <p>If the sequence is mutated while the stream is being read, the result
171 * is undefined.
172 *
173 * @return an IntStream of Unicode code points from this sequence
174 * @since 1.8
175 */
176 public default IntStream codePoints() {
177 class CodePointIterator implements PrimitiveIterator.OfInt {
178 int cur = 0;
179
180 @Override
181 public void forEachRemaining(IntConsumer block) {
182 while (cur < length()) {
183 int cp = Character.codePointAt(CharSequence.this, cur);
184 cur += Character.charCount(cp);
185 block.accept(cp);
186 }
187 }
188
189 public boolean hasNext() {
190 return cur < length();
191 }
192
193 public int nextInt() {
194 if (!hasNext()) {
195 throw new NoSuchElementException();
196 }
197 int cp = Character.codePointAt(CharSequence.this, cur);
198 cur += Character.charCount(cp);
199 return cp;
200 }
201 }
202
203 return StreamSupport.intStream(() ->
204 Spliterators.spliteratorUnknownSize(
205 new CodePointIterator(),
206 Spliterator.ORDERED),
207 Spliterator.SUBSIZED | Spliterator.SIZED | Spliterator.ORDERED);
208 }
209 }