001 /*
002 * Copyright 2000-2003 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package java.lang;
027
028 /**
029 * A <tt>CharSequence</tt> is a readable sequence of <code>char</code> values. This
030 * interface provides uniform, read-only access to many different kinds of
031 * <code>char</code> sequences.
032 * A <code>char</code> value represents a character in the <i>Basic
033 * Multilingual Plane (BMP)</i> or a surrogate. Refer to <a
034 * href="Character.html#unicode">Unicode Character Representation</a> for details.
035 *
036 * <p> This interface does not refine the general contracts of the {@link
037 * java.lang.Object#equals(java.lang.Object) equals} and {@link
038 * java.lang.Object#hashCode() hashCode} methods. The result of comparing two
039 * objects that implement <tt>CharSequence</tt> is therefore, in general,
040 * undefined. Each object may be implemented by a different class, and there
041 * is no guarantee that each class will be capable of testing its instances
042 * for equality with those of the other. It is therefore inappropriate to use
043 * arbitrary <tt>CharSequence</tt> instances as elements in a set or as keys in
044 * a map. </p>
045 *
046 * @author Mike McCloskey
047 * @version 1.15 07/05/05
048 * @since 1.4
049 * @spec JSR-51
050 */
051
052 public interface CharSequence {
053
054 /**
055 * Returns the length of this character sequence. The length is the number
056 * of 16-bit <code>char</code>s in the sequence.</p>
057 *
058 * @return the number of <code>char</code>s in this sequence
059 */
060 int length();
061
062 /**
063 * Returns the <code>char</code> value at the specified index. An index ranges from zero
064 * to <tt>length() - 1</tt>. The first <code>char</code> value of the sequence is at
065 * index zero, the next at index one, and so on, as for array
066 * indexing. </p>
067 *
068 * <p>If the <code>char</code> value specified by the index is a
069 * <a href="Character.html#unicode">surrogate</a>, the surrogate
070 * value is returned.
071 *
072 * @param index the index of the <code>char</code> value to be returned
073 *
074 * @return the specified <code>char</code> value
075 *
076 * @throws IndexOutOfBoundsException
077 * if the <tt>index</tt> argument is negative or not less than
078 * <tt>length()</tt>
079 */
080 char charAt(int index);
081
082 /**
083 * Returns a new <code>CharSequence</code> that is a subsequence of this sequence.
084 * The subsequence starts with the <code>char</code> value at the specified index and
085 * ends with the <code>char</code> value at index <tt>end - 1</tt>. The length
086 * (in <code>char</code>s) of the
087 * returned sequence is <tt>end - start</tt>, so if <tt>start == end</tt>
088 * then an empty sequence is returned. </p>
089 *
090 * @param start the start index, inclusive
091 * @param end the end index, exclusive
092 *
093 * @return the specified subsequence
094 *
095 * @throws IndexOutOfBoundsException
096 * if <tt>start</tt> or <tt>end</tt> are negative,
097 * if <tt>end</tt> is greater than <tt>length()</tt>,
098 * or if <tt>start</tt> is greater than <tt>end</tt>
099 */
100 CharSequence subSequence(int start, int end);
101
102 /**
103 * Returns a string containing the characters in this sequence in the same
104 * order as this sequence. The length of the string will be the length of
105 * this sequence. </p>
106 *
107 * @return a string consisting of exactly this sequence of characters
108 */
109 public String toString();
110
111 }
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