Source for java.io.Writer

   1: /* Writer.java -- Base class for character output streams
   2:    Copyright (C) 1998, 1999, 2001, 2003, 2004, 2005  Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10:  
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package java.io;
  40: 
  41: /* Written using "Java Class Libraries", 2nd edition, plus online
  42:  * API docs for JDK 1.2 beta from http://www.javasoft.com.
  43:  * Status:  Believed complete and correct.
  44:  */
  45: 
  46: /**
  47:  * This abstract class forms the base of the hierarchy of classes that 
  48:  * write output as a stream of chars.  It provides a common set of methods
  49:  * for writing chars to stream.  Subclasses implement and/or extend these
  50:  * methods to write chars in a particular manner or to a particular 
  51:  * destination such as a file on disk or network connection.
  52:  *
  53:  * @author Aaron M. Renn (arenn@urbanophile.com)
  54:  * @author Per Bothner (bothner@cygnus.com)
  55:  */
  56: public abstract class Writer implements Appendable, Closeable, Flushable
  57: {
  58:   /**
  59:    * This is the object used to synchronize criticial code sections for
  60:    * thread safety.  Subclasses should use this field instead of using
  61:    * synchronized methods or explicity synchronizations on <code>this</code>
  62:    */
  63:   protected Object lock;
  64: 
  65:   /**
  66:    * This is the default no-argument constructor for this class.  This method
  67:    * will set up the class to synchronize criticial sections on itself.
  68:    */
  69:   protected Writer()
  70:   {
  71:     lock = this;
  72:   }
  73: 
  74:   /**
  75:    * This method initializes a <code>Writer</code> that will synchronize
  76:    * on the specified <code>Object</code>.
  77:    *
  78:    * @param lock The <code>Object</code> to use for synchronizing critical
  79:    *             sections. Must not be null.
  80:    */
  81:   protected Writer(Object lock)
  82:   {
  83:     if (lock == null)
  84:       throw new NullPointerException();
  85: 
  86:     this.lock = lock;
  87:   }
  88: 
  89:   /**
  90:    * This method forces any data that may have been buffered to be written
  91:    * to the underlying output device.  Please note that the host environment
  92:    * might perform its own buffering unbeknowst to Java.  In that case, a
  93:    * write made (for example, to a disk drive) might be cached in OS
  94:    * buffers instead of actually being written to disk.
  95:    *
  96:    * @exception IOException If an error occurs
  97:    */
  98:   public abstract void flush() throws IOException;
  99: 
 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: }