org.apache.avalon.framework
Class Enum

java.lang.Object
  |
  +--org.apache.avalon.framework.Enum
Direct Known Subclasses:
ValuedEnum

public abstract class Enum
extends Object

Basic enum class for type-safe enums. Should be used as an abstract base. For example:

 import org.apache.avalon.framework.Enum;

 public final class Color extends Enum {
   public static final Color RED = new Color( "Red" );
   public static final Color GREEN = new Color( "Green" );
   public static final Color BLUE = new Color( "Blue" );

   private Color( final String color )
   {
     super( color );
   }
 }
 
If further operations, such as iterating over all items, are required, the Enum(String, Map) constructor can be used to populate a Map, from which further functionality can be derived:
 public final class Color extends Enum {
   static final Map map = new HashMap();

   public static final Color RED = new Color( "Red", map );
   public static final Color GREEN = new Color( "Green", map );
   public static final Color BLUE = new Color( "Blue", map );

   private Color( final String color, final Map map )
   {
     super( color, map );
   }

   public static Iterator iterator()
   {
     return map.values().iterator();
   }
 }
 

NOTE: between 4.0 and 4.1, the constructors' access has been changed from public to protected. This is to prevent users of the Enum breaking type-safety by defining new Enum items. All Enum items should be defined in the Enum class, as shown above.

Version:
CVS $Revision: 1.23 $ $Date: 2003/02/11 15:58:37 $
Author:
Avalon Development Team

Constructor Summary
protected Enum(String name)
          Constructor to add a new named item.
protected Enum(String name, Map map)
          Constructor to add a new named item.
 
Method Summary
 boolean equals(Object other)
          Tests for equality.
 String getName()
          Retrieve the name of this Enum item, set in the constructor.
 int hashCode()
          Returns a hash code value for the object.
 String toString()
          Human readable description of this Enum item.
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Constructor Detail

Enum

protected Enum(String name)
Constructor to add a new named item.

Note: access changed from public to protected after 4.0. See class description.

Parameters:
name - Name of the item.

Enum

protected Enum(String name,
               Map map)
Constructor to add a new named item.

Note: access changed from public to protected after 4.0. See class description.

Parameters:
name - Name of the item.
map - A Map, to which will be added a pointer to the newly constructed object.
Method Detail

equals

public final boolean equals(Object other)
Tests for equality. Two Enum:s are considered equal if they have the same class names and the same names. Identity is tested for first, so this method runs fast. The method is also declared final - I (LSutic) did this to allow the JIT to inline it easily.

Overrides:
equals in class Object
Parameters:
other - the other object
Returns:
the equality status

hashCode

public int hashCode()
Returns a hash code value for the object.

Overrides:
hashCode in class Object
Returns:
a hash code value for this object

getName

public final String getName()
Retrieve the name of this Enum item, set in the constructor.

Returns:
the name String of this Enum item

toString

public String toString()
Human readable description of this Enum item. For use when debugging.

Overrides:
toString in class Object
Returns:
String in the form type[name], eg.: Color[Red].


Copyright © 2001 Apache Jakarta Project. All Rights Reserved.