001 /* CharSequence.java -- Anything that has an indexed sequence of chars
002 Copyright (C) 2001, 2002 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
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017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038
039 package java.lang;
040
041 /**
042 * General functions on a sequence of chars. This interface is implemented
043 * by <code>String</code>, <code>StringBuffer</code> and
044 * <code>CharBuffer</code> to give a uniform way to get chars at a certain
045 * index, the number of characters in the sequence and a subrange of the
046 * chars. Indexes start at 0 and the last index is <code>length()-1</code>.
047 *
048 * <p>Even when classes implement this interface they are not always
049 * exchangeble because they might implement their compare, equals or hash
050 * function differently. This means that in general one should not use a
051 * <code>CharSequence</code> as keys in collections since two sequences
052 * with the same chars at the same indexes with the same length might not
053 * have the same hash code, be equal or be comparable since the are
054 * represented by different classes.
055 *
056 * @author Mark Wielaard (mark@klomp.org)
057 * @since 1.4
058 * @status updated to 1.4
059 */
060 public interface CharSequence
061 {
062 /**
063 * Returns the character at the given index.
064 *
065 * @param i the index to retrieve from
066 * @return the character at that location
067 * @throws IndexOutOfBoundsException if i < 0 || i >= length() - 1
068 */
069 char charAt(int i);
070
071 /**
072 * Returns the length of the sequence. This is the number of 16-bit
073 * characters in the sequence, which may differ from the length of the
074 * underlying encoding.
075 *
076 * @return the sequence length
077 */
078 int length();
079
080 /**
081 * Returns a new <code>CharSequence</code> of the indicated range.
082 *
083 * @param begin the start index (inclusive)
084 * @param end the end index (exclusive)
085 * @return a subsequence of this
086 * @throws IndexOutOfBoundsException if begin > end || begin < 0 ||
087 * end > length()
088 */
089 CharSequence subSequence(int begin, int end);
090
091 /**
092 * Returns the complete <code>CharSequence</code> as a <code>String</code>.
093 * Classes that implement this interface should return a <code>String</code>
094 * which contains only the characters in the sequence in the correct order.
095 *
096 * @return the character sequence as a String
097 */
098 String toString();
099 }