org.apache.commons.collections.map
public class LazyMap extends AbstractMapDecorator implements Map, Serializable
Map
to create objects in the map on demand.
When the get 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.
Note that LazyMap is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. The simplest approach is to wrap this map using java.util.Collections#synchronizedMap(Map). This class may throw exceptions when accessed by concurrent threads without synchronization.
This class is Serializable from Commons Collections 3.1.
Since: Commons Collections 3.0
Version: $Revision: 348007 $ $Date: 2005-11-21 22:52:57 +0000 (Mon, 21 Nov 2005) $
Field Summary | |
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protected Transformer | factory The factory to use to construct elements |
Constructor Summary | |
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protected | LazyMap(Map map, Factory factory)
Constructor that wraps (not copies).
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protected | LazyMap(Map map, Transformer factory)
Constructor that wraps (not copies).
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Method Summary | |
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static Map | decorate(Map map, Factory factory)
Factory method to create a lazily instantiated map.
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static Map | decorate(Map map, Transformer factory)
Factory method to create a lazily instantiated map.
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Object | get(Object key) |
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
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
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
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