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. 015 016 You should have received a copy of the GNU General Public License 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 }