/*

 * 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

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

 *

 * 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.

 *

 */

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="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();

}