libjava/java/lang/CharSequence.java

/* java.lang.CharSequence -- Anything that has an indexed sequence of chars
   Copyright (C) 2001 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
 
GNU Classpath 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 for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

As a special exception, if you link this library with other files to
produce an executable, this library does not by itself cause the
resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why the
executable file might be covered by the GNU General Public License. */


package java.lang;

/**
 * General functions on a sequence of chars. This interface is implemented
 * by <code>String</code>, <code>StringBuffer</code> and
 * <code>CharBuffer</code> to give a uniform way to get chars at a certain
 * index, the number of characters in the sequence and a subrange of the
 * chars. Indexes start at 0 and the last index is <code>length()-1</code>.
 * <p>
 * Even when classes implement this interface they are not always
 * exchangeble because they might implement their compare, equals or hash
 * function differently. This means that in general one should not use a
 * <code>CharSequence</code> as keys in collections since two sequences
 * with the same chars at the same indexes with the same length might not
 * have the same hash code, be equal or be comparable since the are
 * represented by different classes.
 *
 * @author Mark Wielaard (mark@klomp.org)
 *
 * @since 1.4
 */

public interface CharSequence {

    /**
     * Returns the character at the given index.
     *
     * @exception IndexOutOfBoundsException when <code>i &lt; 0</code> or
     * <code>i &gt; length()-1</code>.
     */
    char charAt(int i);

    /**
     * Returns the length of the sequence.
     */
    int length();

    /**
     * Returns a new <code>CharSequence</char> of the indicated range.
     *
     * @exception IndexOutOfBoundsException when <code>begin &lt; 0</code>,
     *         <code>end &lt; 0</code>, <code>end &gt; length()</code> or
     *         <code>begin &gt; end</code>
     */
    CharSequence subSequence(int begin, int end);

    /**
     * Returns the complete <code>CharSequence</code> as a <code>String</code>.
     * Classes that implement this interface should return a <code>String</code>
     * which contains only the characters in the sequence in the correct order.
     */
    String toString();
}