K - the type of the keys in this mapV - the type of the values in this mappublic class LazyMap<K,V> extends AbstractMapDecorator<K,V> implements 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<Date> factory = new Factory<Date>() {
public Date create() {
return new Date();
}
}
Map<String, Date> lazy = LazyMap.lazyMap(new HashMap<String, Date>(), factory);
Date date = lazy.get("NOW");
After the above code is executed, date will refer to
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<? super K,? extends V> |
factory
The factory to use to construct elements
|
| Modifier | Constructor and Description |
|---|---|
protected |
LazyMap(Map<K,V> map,
Factory<? extends V> factory)
Constructor that wraps (not copies).
|
protected |
LazyMap(Map<K,V> map,
Transformer<? super K,? extends V> factory)
Constructor that wraps (not copies).
|
| Modifier and Type | Method and Description |
|---|---|
V |
get(Object key) |
static <K,V> LazyMap<K,V> |
lazyMap(Map<K,V> map,
Factory<? extends V> factory)
Factory method to create a lazily instantiated map.
|
static <V,K> LazyMap<K,V> |
lazyMap(Map<K,V> map,
Transformer<? super K,? extends V> factory)
Factory method to create a lazily instantiated map.
|
clear, containsKey, containsValue, decorated, entrySet, equals, hashCode, isEmpty, keySet, put, putAll, remove, size, toString, valuesmapIteratorclone, finalize, getClass, notify, notifyAll, wait, wait, waitcompute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAllprotected final Transformer<? super K,? extends V> factory
protected LazyMap(Map<K,V> map, Factory<? extends V> factory)
map - the map to decorate, must not be nullfactory - the factory to use, must not be nullNullPointerException - if map or factory is nullprotected LazyMap(Map<K,V> map, Transformer<? super K,? extends V> factory)
map - the map to decorate, must not be nullfactory - the factory to use, must not be nullNullPointerException - if map or factory is nullpublic static <K,V> LazyMap<K,V> lazyMap(Map<K,V> map, Factory<? extends V> factory)
K - the key typeV - the value typemap - the map to decorate, must not be nullfactory - the factory to use, must not be nullNullPointerException - if map or factory is nullpublic static <V,K> LazyMap<K,V> lazyMap(Map<K,V> map, Transformer<? super K,? extends V> factory)
K - the key typeV - the value typemap - the map to decorate, must not be nullfactory - the factory to use, must not be nullNullPointerException - if map or factory is nullpublic V get(Object key)
get in interface Map<K,V>get in interface Get<K,V>get in class AbstractMapDecorator<K,V>key - the key whose associated value is to be returnednull if this map contains no mapping for the keyMap.get(Object)Copyright © 2001–2018 The Apache Software Foundation. All rights reserved.