001 /* Writer.java -- Base class for character output streams 002 Copyright (C) 1998, 1999, 2001, 2003, 2004, 2005 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.io; 040 041 /* Written using "Java Class Libraries", 2nd edition, plus online 042 * API docs for JDK 1.2 beta from http://www.javasoft.com. 043 * Status: Believed complete and correct. 044 */ 045 046 /** 047 * This abstract class forms the base of the hierarchy of classes that 048 * write output as a stream of chars. It provides a common set of methods 049 * for writing chars to stream. Subclasses implement and/or extend these 050 * methods to write chars in a particular manner or to a particular 051 * destination such as a file on disk or network connection. 052 * 053 * @author Aaron M. Renn (arenn@urbanophile.com) 054 * @author Per Bothner (bothner@cygnus.com) 055 */ 056 public abstract class Writer implements Appendable, Closeable, Flushable 057 { 058 /** 059 * This is the object used to synchronize criticial code sections for 060 * thread safety. Subclasses should use this field instead of using 061 * synchronized methods or explicity synchronizations on <code>this</code> 062 */ 063 protected Object lock; 064 065 /** 066 * This is the default no-argument constructor for this class. This method 067 * will set up the class to synchronize criticial sections on itself. 068 */ 069 protected Writer() 070 { 071 lock = this; 072 } 073 074 /** 075 * This method initializes a <code>Writer</code> that will synchronize 076 * on the specified <code>Object</code>. 077 * 078 * @param lock The <code>Object</code> to use for synchronizing critical 079 * sections. Must not be null. 080 */ 081 protected Writer(Object lock) 082 { 083 if (lock == null) 084 throw new NullPointerException(); 085 086 this.lock = lock; 087 } 088 089 /** 090 * This method forces any data that may have been buffered to be written 091 * to the underlying output device. Please note that the host environment 092 * might perform its own buffering unbeknowst to Java. In that case, a 093 * write made (for example, to a disk drive) might be cached in OS 094 * buffers instead of actually being written to disk. 095 * 096 * @exception IOException If an error occurs 097 */ 098 public abstract void flush() throws IOException; 099 100 /** 101 * This method closes the stream. Any internal or native resources 102 * associated 103 * with this stream are freed. Any subsequent attempt to access the stream 104 * might throw an exception. 105 * <p> 106 * This method in this class does nothing. 107 * 108 * @exception IOException If an error occurs 109 */ 110 public abstract void close() throws IOException; 111 112 /** 113 * This method writes a single char to the output stream. 114 * 115 * @param b The char to be written to the output stream, passed as an int 116 * 117 * @exception IOException If an error occurs 118 */ 119 public void write(int b) throws IOException 120 { 121 char[] buf = new char[1]; 122 123 buf[0] = (char)b; 124 write(buf, 0, buf.length); 125 } 126 127 /** 128 * This method all the writes char from the passed array to the output 129 * stream. This method is equivalent to 130 * <code>write(buf, 0, buf.length)</code> which 131 * is exactly how it is implemented in this class. 132 * 133 * @param buf The array of char to write 134 * 135 * @exception IOException If an error occurs 136 */ 137 public void write(char[] buf) throws IOException 138 { 139 write(buf, 0, buf.length); 140 } 141 142 /** 143 * This method writes <code>len</code> char from the specified array 144 * <code>buf</code> starting at index <code>offset</code> into the array. 145 * <p> 146 * Subclasses must provide an implementation of this abstract method. 147 * 148 * @param buf The array of char to write from 149 * @param offset The index into the array to start writing from 150 * @param len The number of char to write 151 * 152 * @exception IOException If an error occurs 153 */ 154 public abstract void write(char[] buf, int offset, int len) 155 throws IOException; 156 157 /** 158 * This method writes all the characters in a <code>String</code> to the 159 * output. 160 * 161 * @param str The <code>String</code> whose chars are to be written. 162 * 163 * @exception IOException If an error occurs 164 */ 165 public void write(String str) throws IOException 166 { 167 write(str, 0, str.length()); 168 } 169 170 /** 171 * This method writes <code>len</code> chars from the <code>String</code> 172 * starting at position <code>offset</code>. 173 * 174 * @param str The <code>String</code> that is to be written 175 * @param offset The character offset into the <code>String</code> to start 176 * writing from 177 * @param len The number of chars to write 178 * 179 * @exception IOException If an error occurs 180 */ 181 public void write(String str, int offset, int len) throws IOException 182 { 183 // FIXME - for libgcj re-write using native code to not require 184 // copied buffer. 185 char[] buf = new char[len]; 186 187 str.getChars(offset, offset + len, buf, 0); 188 write(buf, 0, len); 189 } 190 191 /** @since 1.5 */ 192 public Writer append(char c) throws IOException 193 { 194 write(c); 195 return this; 196 } 197 198 /** @since 1.5 */ 199 public Writer append(CharSequence cs) throws IOException 200 { 201 write(cs == null ? "null" : cs.toString()); 202 return this; 203 } 204 205 /** @since 1.5 */ 206 public Writer append(CharSequence cs, int start, int end) throws IOException 207 { 208 write(cs == null ? "null" : cs.subSequence(start, end).toString()); 209 return this; 210 } 211 }