java.lang.CharSequence Java Source 1.6.0


01/*
02 * @(#)CharSequence.java	1.9 05/11/17
03 *
04 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
05 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
06 */
07
08package java.lang;
09
10
11/**
12 * A <tt>CharSequence</tt> is a readable sequence of <code>char</code> values. This
13 * interface provides uniform, read-only access to many different kinds of
14 * <code>char</code> sequences.
15 * A <code>char</code> value represents a character in the <i>Basic
16 * Multilingual Plane (BMP)</i> or a surrogate. Refer to <a
17 * href="Character.html#unicode">Unicode Character Representation</a> for details.
18 *
19 * <p> This interface does not refine the general contracts of the {@link
20 * java.lang.Object#equals(java.lang.Object) equals} and {@link
21 * java.lang.Object#hashCode() hashCode} methods.  The result of comparing two
22 * objects that implement <tt>CharSequence</tt> is therefore, in general,
23 * undefined.  Each object may be implemented by a different class, and there
24 * is no guarantee that each class will be capable of testing its instances
25 * for equality with those of the other.  It is therefore inappropriate to use
26 * arbitrary <tt>CharSequence</tt> instances as elements in a set or as keys in
27 * a map. </p>
28 *
29 * @author Mike McCloskey
30 * @version 1.9 05/11/17
31 * @since 1.4
32 * @spec JSR-51
33 */
34
35public interface CharSequence {
36
37    /**
38     * Returns the length of this character sequence.  The length is the number
39     * of 16-bit <code>char</code>s in the sequence.</p>
40     *
41     * @return  the number of <code>char</code>s in this sequence
42     */
43    int length();
44
45    /**
46     * Returns the <code>char</code> value at the specified index.  An index ranges from zero
47     * to <tt>length() - 1</tt>.  The first <code>char</code> value of the sequence is at
48     * index zero, the next at index one, and so on, as for array
49     * indexing. </p>
50     *
51     * <p>If the <code>char</code> value specified by the index is a
52     * <a href="Character.html#unicode">surrogate</a>, the surrogate
53     * value is returned.
54     *
55     * @param   index   the index of the <code>char</code> value to be returned
56     *
57     * @return  the specified <code>char</code> value
58     *
59     * @throws  IndexOutOfBoundsException
60     *          if the <tt>index</tt> argument is negative or not less than
61     *          <tt>length()</tt>
62     */
63    char charAt(int index);
64
65    /**
66     * Returns a new <code>CharSequence</code> that is a subsequence of this sequence.
67     * The subsequence starts with the <code>char</code> value at the specified index and
68     * ends with the <code>char</code> value at index <tt>end - 1</tt>.  The length
69     * (in <code>char</code>s) of the
70     * returned sequence is <tt>end - start</tt>, so if <tt>start == end</tt>
71     * then an empty sequence is returned. </p>
72     * 
73     * @param   start   the start index, inclusive
74     * @param   end     the end index, exclusive
75     *
76     * @return  the specified subsequence
77     *
78     * @throws  IndexOutOfBoundsException
79     *          if <tt>start</tt> or <tt>end</tt> are negative,
80     *          if <tt>end</tt> is greater than <tt>length()</tt>,
81     *          or if <tt>start</tt> is greater than <tt>end</tt>
82     */
83    CharSequence subSequence(int start, int end);
84
85    /**
86     * Returns a string containing the characters in this sequence in the same
87     * order as this sequence.  The length of the string will be the length of
88     * this sequence. </p>
89     *
90     * @return  a string consisting of exactly this sequence of characters
91     */
92    public String toString();
93
94}