org.apache.commons.collections.map
Class LazyMap
java.lang.Object
|
+--org.apache.commons.collections.map.AbstractMapDecorator
|
+--org.apache.commons.collections.map.LazyMap
- All Implemented Interfaces:
- Map
- Direct Known Subclasses:
- LazySortedMap
- public class LazyMap
- extends AbstractMapDecorator
- implements Map
Decorates another Map
to create objects in the map on demand.
When the get(Object)
method is called with a key that does not
exist in the map, the factory is used to create the object. The created
object will be added to the map using the requested key.
For instance:
Factory factory = new Factory() {
public Object create() {
return new Date();
}
}
Map lazy = Lazy.map(new HashMap(), factory);
Object obj = lazy.get("NOW");
After the above code is executed, obj
will contain
a new Date
instance. Furthermore, that Date
instance is mapped to the "NOW" key in the map.
- Since:
- Commons Collections 3.0
- Version:
- $Revision: 1.3 $ $Date: 2004/01/14 21:43:11 $
- Author:
- Stephen Colebourne, Paul Jack
Methods inherited from class org.apache.commons.collections.map.AbstractMapDecorator |
clear, containsKey, containsValue, entrySet, equals, getMap, hashCode, isEmpty, keySet, put, putAll, remove, size, toString, values |
Methods inherited from interface java.util.Map |
clear, containsKey, containsValue, entrySet, equals, hashCode, isEmpty, keySet, put, putAll, remove, size, values |
factory
protected final Transformer factory
- The factory to use to construct elements
LazyMap
protected LazyMap(Map map,
Factory factory)
- Constructor that wraps (not copies).
- Parameters:
map
- the map to decorate, must not be nullfactory
- the factory to use, must not be null- Throws:
IllegalArgumentException
- if map or factory is null
LazyMap
protected LazyMap(Map map,
Transformer factory)
- Constructor that wraps (not copies).
- Parameters:
map
- the map to decorate, must not be nullfactory
- the factory to use, must not be null- Throws:
IllegalArgumentException
- if map or factory is null
decorate
public static Map decorate(Map map,
Factory factory)
- Factory method to create a lazily instantiated map.
- Parameters:
map
- the map to decorate, must not be nullfactory
- the factory to use, must not be null- Throws:
IllegalArgumentException
- if map or factory is null
decorate
public static Map decorate(Map map,
Transformer factory)
- Factory method to create a lazily instantiated map.
- Parameters:
map
- the map to decorate, must not be nullfactory
- the factory to use, must not be null- Throws:
IllegalArgumentException
- if map or factory is null
get
public Object get(Object key)
- Specified by:
get
in interface Map
- Overrides:
get
in class AbstractMapDecorator
Copyright © 2001-2004 Apache Software Foundation. All Rights Reserved.