libjava/java/io/Writer.java

   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., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 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
  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 } // class Writer
 192