libjava/java/awt/AttributeValue.java

   1 /* AttributeValue.java -- parent of type-safe enums of attributes
   2    Copyright (C) 2002, 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.awt;
  40
  41 /**
  42  * This class is undocumented by Sun, but it is the parent of several other
  43  * classes, all of which are type-safe enumerations. This takes care of
  44  * <code>equals</code>, <code>toString</code>, and <code>hashCode</code>, so
  45  * that you don't have to (although hashCode is commonly overridden).
  46  *
  47  * @author Eric Blake (ebb9@email.byu.edu)
  48  */
  49 class AttributeValue
  50 {
  51   /** The value of the enumeration. Package visible for speed. */
  52   final int value;
  53
  54   /** The list of enumeration names for the given subclass. */
  55   private final String[] names;
  56
  57   /**
  58    * Construct a type-safe enumeration element. For example,<br>
  59    * <pre>
  60    * class Foo extends AttributeValue
  61    * {
  62    *   private static final String[] names = { "one", "two" }
  63    *   public static final Foo ONE = new Foo(0);
  64    *   public static final Foo TWO = new Foo(1);
  65    *   private Foo(int value) { super(value, names); }
  66    * }
  67    * </pre>
  68    *
  69    * @param value the position of this enumeration element, consecutive from 0
  70    * @param names the constant list of enumeration names for the subclass
  71    */
  72   AttributeValue(int value, String[] names)
  73   {
  74     this.value = value;
  75     this.names = names;
  76   }
  77
  78   /**
  79    * Returns the hashcode of this element. This is the index of the element
  80    * in the enumeration. Note that equals defaults to the == relation.
  81    *
  82    * @return the hashcode
  83    */
  84   public int hashCode()
  85   {
  86     return value;
  87   }
  88
  89   /**
  90    * Returns the name of this enumeration element.
  91    *
  92    * @return the element name
  93    */
  94   public String toString()
  95   {
  96     return names[value];
  97   }
  98 } // class AttributeValue