libjava/java/io/Writer.java

   1 /* Writer.java -- Base class for character output streams
   2    Copyright (C) 1998, 1999, 2001, 2003 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 obj The <code>Object</code> to use for synchronizing critical
  79    *            sections
  80    */
  81   protected Writer(Object lock)
  82   {
  83     this.lock = lock;
  84   }
  85
  86   /**
  87    * This method forces any data that may have been buffered to be written
  88    * to the underlying output device.  Please note that the host environment
  89    * might perform its own buffering unbeknowst to Java.  In that case, a
  90    * write made (for example, to a disk drive) might be cached in OS
  91    * buffers instead of actually being written to disk.
  92    *
  93    * @exception IOException If an error occurs
  94    */
  95   public abstract void flush() throws IOException;
  96
  97   /**
  98    * This method closes the stream.  Any internal or native resources
  99    * associated
 100    * with this stream are freed.  Any subsequent attempt to access the stream
 101    * might throw an exception.
 102    * <p>
 103    * This method in this class does nothing.
 104    *
 105    * @exception IOException If an error occurs
 106    */
 107   public abstract void close() throws IOException;
 108
 109   /**
 110    * This method writes a single char to the output stream.
 111    *
 112    * @param b The char to be written to the output stream, passed as an int
 113    *
 114    * @exception IOException If an error occurs
 115    */
 116   public void write(int b) throws IOException
 117   {
 118     char[] buf = new char[1];
 119
 120     buf[0] = (char)b;
 121     write(buf, 0, buf.length);
 122   }
 123
 124   /**
 125    * This method all the writes char from the passed array to the output
 126    * stream. This method is equivalent to
 127    * <code>write(buf, 0, buf.length)</code> which
 128    * is exactly how it is implemented in this class.
 129    *
 130    * @param buf The array of char to write
 131    *
 132    * @exception IOException If an error occurs
 133    */
 134   public void write(char[] buf) throws IOException
 135   {
 136     write(buf, 0, buf.length);
 137   }
 138
 139   /**
 140    * This method writes <code>len</code> char from the specified array
 141    * <code>buf</code> starting at index <code>offset</code> into the array.
 142    * <p>
 143    * Subclasses must provide an implementation of this abstract method.
 144    *
 145    * @param buf The array of char to write from
 146    * @param offset The index into the array to start writing from
 147    * @param len The number of char to write
 148    *
 149    * @exception IOException If an error occurs
 150    */
 151   public abstract void write(char[] buf, int offset, int len)
 152     throws IOException;
 153
 154   /**
 155    * This method writes all the characters in a <code>String</code> to the
 156    * output.
 157    *
 158    * @param str The <code>String</code> whose chars are to be written.
 159    *
 160    * @param IOException If an error occurs
 161    */
 162   public void write(String str) throws IOException
 163   {
 164     write(str, 0, str.length());
 165   }
 166
 167   /**
 168    * This method writes <code>len</code> chars from the <code>String</code>
 169    * starting at position <code>offset</code>.
 170    *
 171    * @param str The <code>String</code> that is to be written
 172    * @param offset The character offset into the <code>String</code> to start
 173    *               writing from
 174    * @param len The number of chars to write
 175    *
 176    * @exception IOException If an error occurs
 177    */
 178   public void write(String str, int offset, int len) throws IOException
 179   {
 180     // FIXME - for libgcj re-write using native code to not require
 181     // copied buffer.
 182     char[] buf = new char[len];
 183
 184     str.getChars(offset, offset + len, buf, 0);
 185     write(buf, 0, len);
 186   }
 187
 188 } // class Writer
 189