public class LazyMap extends AbstractMapDecorator implements Map, Serializable
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.
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 Collections.synchronizedMap(Map). This class may throw
exceptions when accessed by concurrent threads without synchronization.
This class is Serializable from Commons Collections 3.1.
| Modifier and Type | Field and Description |
|---|---|
protected Transformer |
factory
The factory to use to construct elements
|
map| Modifier | Constructor and Description |
|---|---|
protected |
LazyMap(Map map,
Factory factory)
Constructor that wraps (not copies).
|
protected |
LazyMap(Map map,
Transformer factory)
Constructor that wraps (not copies).
|
| Modifier and Type | Method and Description |
|---|---|
static Map |
decorate(Map map,
Factory factory)
Factory method to create a lazily instantiated map.
|
static Map |
decorate(Map map,
Transformer factory)
Factory method to create a lazily instantiated map.
|
Object |
get(Object key) |
clear, containsKey, containsValue, entrySet, equals, getMap, hashCode, isEmpty, keySet, put, putAll, remove, size, toString, valuesprotected final Transformer factory
protected LazyMap(Map map, Factory factory)
map - the map to decorate, must not be nullfactory - the factory to use, must not be nullIllegalArgumentException - if map or factory is nullprotected LazyMap(Map map, Transformer factory)
map - the map to decorate, must not be nullfactory - the factory to use, must not be nullIllegalArgumentException - if map or factory is nullpublic static Map decorate(Map map, Factory factory)
map - the map to decorate, must not be nullfactory - the factory to use, must not be nullIllegalArgumentException - if map or factory is nullpublic static Map decorate(Map map, Transformer factory)
map - the map to decorate, must not be nullfactory - the factory to use, must not be nullIllegalArgumentException - if map or factory is nullCopyright © 2001–2015 The Apache Software Foundation. All rights reserved.