001/* CharSequence.java -- Anything that has an indexed sequence of chars 002 Copyright (C) 2001, 2002 Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038 039package 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 */ 060public 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}