gomp-20050608-branch/libjava/classpath/javax/print/attribute/EnumSyntax.java

   1 /* EnumSyntax.java --
   2    Copyright (C) 2003, 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 package javax.print.attribute;
  39
  40 import java.io.InvalidObjectException;
  41 import java.io.ObjectStreamException;
  42 import java.io.Serializable;
  43
  44 /**
  45  * <code>EnumSyntax</code> is the abstract base class of all enumeration
  46  * classes in the Java Print Service API.
  47  * <p>
  48  * Every enumeration class which extends from EnumSyntax provides several
  49  * enumeration objects as singletons of its class.
  50  * </p>
  51  * <p>
  52  * Notes for implementing subclasses:
  53  * <ul>
  54  *   <li>
  55  *     The values of all enumeration singelton instances have to be in a
  56  *     sequence which may start at any value. See: {@link #getOffset()}
  57  *   </li>
  58  *   <li>
  59  *     Subclasses have to override {@link #getEnumValueTable()} and should
  60  *     override {@link #getStringTable()} for correct serialization.
  61  *   </li>
  62  * </ul>
  63  * </p>
  64  * Example:
  65  * <pre>
  66  * public class PrinterState extends EnumSyntax
  67  * {
  68  *   public static final PrinterState IDLE = new PrinterState(1);
  69  *   public static final PrinterState PROCESSING = new PrinterState(2);
  70  *   public static final PrinterState STOPPED = new PrinterState(3);
  71  *
  72  *   protected PrinterState(int value)
  73  *   {
  74  *     super(value);
  75  *   }
  76  *
  77  *   // Overridden because values start not at zero !
  78  *   protected int getOffset()
  79  *   {
  80  *     return 1;
  81  *   }
  82  *
  83  *   private static final String[] stringTable = { "idle", "processing",
  84  *                                                 "stopped" };
  85  *
  86  *   protected String[] getStringTable()
  87  *   {
  88  *     return stringTable;
  89  *   }
  90  *
  91  *   private static final PrinterState[] enumValueTable = { IDLE,
  92  *                                             PROCESSING, STOPPED};
  93  *
  94  *   protected EnumSyntax[] getEnumValueTable()
  95  *   {
  96  *     return enumValueTable;
  97  *   }
  98  * }
  99  * </pre>
 100  *
 101  * @author Michael Koch (konqueror@gmx.de)
 102  * @author Wolfgang Baer (WBaer@gmx.de)
 103  */
 104 public abstract class EnumSyntax implements Cloneable, Serializable
 105 {
 106   private static final long serialVersionUID = -2739521845085831642L;
 107
 108   private int value;
 109
 110   /**
 111    * Creates a <code>EnumSyntax</code> object.
 112    *
 113    * @param value the value to set.
 114    */
 115   protected EnumSyntax(int value)
 116   {
 117     this.value = value;
 118   }
 119
 120   /**
 121    * Returns the value of this enumeration object.
 122    *
 123    * @return The value.
 124    */
 125   public int getValue()
 126   {
 127     return value;
 128   }
 129
 130   /**
 131    * Clones this object.
 132    *
 133    * @return A clone of this object.
 134    */
 135   public Object clone()
 136   {
 137     try
 138       {
 139         return super.clone();
 140       }
 141     catch (CloneNotSupportedException e)
 142       {
 143         // Cannot happen as we implement java.lang.Cloneable.
 144         return null;
 145       }
 146   }
 147
 148   /**
 149    * Returns the hashcode for this object.
 150    * The hashcode is the value of this enumeration object.
 151    *
 152    * @return The hashcode.
 153    */
 154   public int hashCode()
 155   {
 156     return value;
 157   }
 158
 159   /**
 160    * Returns the string representation for this object.
 161    * The string value from <code>getStringTable()</code> method is returned
 162    * if subclasses override this method. Otherwise the value of this object
 163    * as a string is returned.
 164    *
 165    * @return The string representation.
 166    */
 167   public String toString()
 168   {
 169     int index = value - getOffset();
 170     String[] table = getStringTable();
 171
 172     if (table != null
 173         && index >= 0
 174         && index < table.length)
 175       return table[index];
 176
 177     return "" + value;
 178   }
 179
 180   /**
 181    * Returns a table with the enumeration values represented as strings
 182    * for this object.
 183    *
 184    * The default implementation just returns null. Subclasses should
 185    * override this method.
 186    *
 187    * @return The enumeration values as strings.
 188    */
 189   protected String[] getStringTable()
 190   {
 191     return null;
 192   }
 193
 194   /**
 195    * Needed for singelton semantics during deserialisation.
 196    *
 197    * Subclasses must not override this class. Subclasses have to override
 198    * <code>getEnumValueTable()</code> and should override
 199    * <code>getStringTable()</code> for correct serialization.
 200    *
 201    * @return The Object at index <code>value - getOffset()</code>
 202    *         in getEnumValueTable.
 203    * @throws ObjectStreamException if getEnumValueTable() returns null.
 204    */
 205   protected Object readResolve() throws ObjectStreamException
 206   {
 207     EnumSyntax[] table = getEnumValueTable();
 208     if (table == null)
 209       throw new InvalidObjectException("Null enumeration value table "
 210                                        + "for class "
 211                                        + this.getClass().toString());
 212
 213     return table[value - getOffset()];
 214   }
 215
 216   /**
 217    * Returns a table with the enumeration values for this object.
 218    *
 219    * The default implementation just returns null. Subclasses have to
 220    * to override this method for serialization.
 221    *
 222    * @return The enumeration values.
 223    */
 224   protected EnumSyntax[] getEnumValueTable()
 225   {
 226     return null;
 227   }
 228
 229   /**
 230    * Returns the lowest used value by the enumerations of this class.
 231    *
 232    * The default implementation returns 0. This is enough if enumerations
 233    * start with a zero value. Otherwise subclasses need to override this
 234    * method for serialization and return the lowest value they use.
 235    * .
 236    * @return The lowest used value used.
 237    */
 238   protected int getOffset()
 239   {
 240     return 0;
 241   }
 242 }