1 /*

     2  * Copyright 2000-2003 Sun Microsystems, Inc.  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.  Sun designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    22  * CA 95054 USA or visit www.sun.com if you need additional information or

    23  * have any questions.

    24  */

    25 

    26 package java.lang;

    27 

    28 

    29 /**

    30  * A <tt>CharSequence</tt> is a readable sequence of <code>char</code> values. This

    31  * interface provides uniform, read-only access to many different kinds of

    32  * <code>char</code> sequences.

    33  * A <code>char</code> value represents a character in the <i>Basic

    34  * Multilingual Plane (BMP)</i> or a surrogate. Refer to <a

    35  * href="Character.html#unicode">Unicode Character Representation</a> for details.

    36  *

    37  * <p> This interface does not refine the general contracts of the {@link

    38  * java.lang.Object#equals(java.lang.Object) equals} and {@link

    39  * java.lang.Object#hashCode() hashCode} methods.  The result of comparing two

    40  * objects that implement <tt>CharSequence</tt> is therefore, in general,

    41  * undefined.  Each object may be implemented by a different class, and there

    42  * is no guarantee that each class will be capable of testing its instances

    43  * for equality with those of the other.  It is therefore inappropriate to use

    44  * arbitrary <tt>CharSequence</tt> instances as elements in a set or as keys in

    45  * a map. </p>

    46  *

    47  * @author Mike McCloskey

    48  * @since 1.4

    49  * @spec JSR-51

    50  */

    51 

    52 public interface CharSequence {

    53 

    54     /**

    55      * Returns the length of this character sequence.  The length is the number

    56      * of 16-bit <code>char</code>s in the sequence.</p>

    57      *

    58      * @return  the number of <code>char</code>s in this sequence

    59      */

    60     int length();

    61 

    62     /**

    63      * Returns the <code>char</code> value at the specified index.  An index ranges from zero

    64      * to <tt>length() - 1</tt>.  The first <code>char</code> value of the sequence is at

    65      * index zero, the next at index one, and so on, as for array

    66      * indexing. </p>

    67      *

    68      * <p>If the <code>char</code> value specified by the index is a

    69      * <a href="Character.html#unicode">surrogate</a>, the surrogate

    70      * value is returned.

    71      *

    72      * @param   index   the index of the <code>char</code> value to be returned

    73      *

    74      * @return  the specified <code>char</code> value

    75      *

    76      * @throws  IndexOutOfBoundsException

    77      *          if the <tt>index</tt> argument is negative or not less than

    78      *          <tt>length()</tt>

    79      */

    80     char charAt(int index);

    81 

    82     /**

    83      * Returns a new <code>CharSequence</code> that is a subsequence of this sequence.

    84      * The subsequence starts with the <code>char</code> value at the specified index and

    85      * ends with the <code>char</code> value at index <tt>end - 1</tt>.  The length

    86      * (in <code>char</code>s) of the

    87      * returned sequence is <tt>end - start</tt>, so if <tt>start == end</tt>

    88      * then an empty sequence is returned. </p>

    89      *

    90      * @param   start   the start index, inclusive

    91      * @param   end     the end index, exclusive

    92      *

    93      * @return  the specified subsequence

    94      *

    95      * @throws  IndexOutOfBoundsException

    96      *          if <tt>start</tt> or <tt>end</tt> are negative,

    97      *          if <tt>end</tt> is greater than <tt>length()</tt>,

    98      *          or if <tt>start</tt> is greater than <tt>end</tt>

    99      */

   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 }