/*

  * Copyright (c) 2000, 2003, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

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

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  */

 package java.lang;

 /**

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

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

  * <code>char</code> sequences.

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

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

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

  *

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

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

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

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

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

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

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

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

  * a map. </p>

  *

  * @author Mike McCloskey

  * @since 1.4

  * @spec JSR-51

  */

 public interface CharSequence {

     /**

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

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

      *

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

      */

     int length();

     /**

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

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

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

      * indexing. </p>

      *

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

      * <a href="{@docRoot}/java/lang/Character.html#unicode">surrogate</a>, the surrogate

      * value is returned.

      *

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

      *

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

      *

      * @throws  IndexOutOfBoundsException

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

      *          <tt>length()</tt>

      */

     char charAt(int index);

     /**

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

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

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

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

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

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

      *

      * @param   start   the start index, inclusive

      * @param   end     the end index, exclusive

      *

      * @return  the specified subsequence

      *

      * @throws  IndexOutOfBoundsException

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

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

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

      */

     CharSequence subSequence(int start, int end);

     /**

      * Returns a string containing the characters in this sequence in the same

      * order as this sequence.  The length of the string will be the length of

      * this sequence. </p>

      *

      * @return  a string consisting of exactly this sequence of characters

      */

     public String toString();

 }