org.apache.commons.collections.map
Class LazyMap<K,V>

java.lang.Object
  org.apache.commons.collections.map.AbstractMapDecorator<K,V>
      org.apache.commons.collections.map.LazyMap<K,V>

All Implemented Interfaces:

Serializable, Map<K,V>

Direct Known Subclasses:

LazySortedMap

public class LazyMap<K,V>
extends AbstractMapDecorator<K,V>
implements Map<K,V>, Serializable

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.

This class is Serializable from Commons Collections 3.1.

Since:

Commons Collections 3.0

Version:

$Revision: 1.1.1.1 $ $Date: 2005/05/23 04:35:53 $

Author:

Stephen Colebourne, Matt Hall, John Watkinson, Paul Jack

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K,V>

Field Summary

protected Factory<V>

factory The factory to use to construct elements

Fields inherited from class org.apache.commons.collections.map.AbstractMapDecorator

map

Constructor Summary

protected

LazyMap(Map<K,V> map, Factory<V> factory) Constructor that wraps (not copies).

Method Summary

static <K,V> Map<K,V>	decorate(Map<K,V> map, Factory<V> factory) Factory method to create a lazily instantiated map.
V	get(Object key)

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 class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

clear, containsKey, containsValue, entrySet, equals, hashCode, isEmpty, keySet, put, putAll, remove, size, values

Field Detail

factory

protected final Factory<V> factory

The factory to use to construct elements

Constructor Detail

LazyMap

protected LazyMap(Map<K,V> map,
                  Factory<V> factory)

Constructor that wraps (not copies).

Parameters:

map - the map to decorate, must not be null

factory - the factory to use, must not be null

Throws:

IllegalArgumentException - if map or factory is null

Method Detail

decorate

public static <K,V> Map<K,V> decorate(Map<K,V> map,
                                      Factory<V> factory)

Factory method to create a lazily instantiated map.

Parameters:

map - the map to decorate, must not be null

factory - the factory to use, must not be null

Throws:

IllegalArgumentException - if map or factory is null

get

public V get(Object key)

Specified by:

get in interface Map<K,V>

Overrides:

get in class AbstractMapDecorator<K,V>