public class DefaultedMap<K,V> extends AbstractMapDecorator<K,V> implements Serializable
Map returning a default value if the map
does not contain the requested key.
When the get(Object) method is called with a key that does not
exist in the map, this map will return the default value specified in
the constructor/factory. Only the get method is altered, so the
Map.containsKey(Object) can be used to determine if a key really
is in the map or not.
The defaulted value is not added to the map.
Compare this behaviour with LazyMap, which does add the value
to the map (via a Transformer).
For instance:
Map map = new DefaultedMap("NULL");
Object obj = map.get("Surname");
// obj == "NULL"
After the above code is executed the map is still empty.
Note that DefaultedMap 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.
LazyMap,
Serialized Form| Modifier | Constructor and Description |
|---|---|
protected |
DefaultedMap(Map<K,V> map,
Transformer<? super K,? extends V> defaultValueTransformer)
Constructor that wraps (not copies).
|
|
DefaultedMap(Transformer<? super K,? extends V> defaultValueTransformer)
Constructs a new empty
DefaultedMap that decorates a HashMap. |
|
DefaultedMap(V defaultValue)
Constructs a new empty
DefaultedMap that decorates
a HashMap. |
| Modifier and Type | Method and Description |
|---|---|
static <K,V> DefaultedMap<K,V> |
defaultedMap(Map<K,V> map,
Factory<? extends V> factory)
Factory method to create a defaulting map.
|
static <K,V> Map<K,V> |
defaultedMap(Map<K,V> map,
Transformer<? super K,? extends V> transformer)
Factory method to create a defaulting map.
|
static <K,V> DefaultedMap<K,V> |
defaultedMap(Map<K,V> map,
V defaultValue)
Factory method to create a defaulting map.
|
V |
get(Object key) |
clear, containsKey, containsValue, decorated, entrySet, equals, hashCode, isEmpty, keySet, put, putAll, remove, size, toString, valuesmapIteratorpublic DefaultedMap(V defaultValue)
DefaultedMap that decorates
a HashMap.
The object passed in will be returned by the map whenever an unknown key is requested.
defaultValue - the default value to return when the key is not foundpublic DefaultedMap(Transformer<? super K,? extends V> defaultValueTransformer)
DefaultedMap that decorates a HashMap.defaultValueTransformer - transformer to use to generate missing values.protected DefaultedMap(Map<K,V> map, Transformer<? super K,? extends V> defaultValueTransformer)
map - the map to decorate, must not be nulldefaultValueTransformer - the value transformer to useIllegalArgumentException - if map or transformer is nullpublic static <K,V> DefaultedMap<K,V> defaultedMap(Map<K,V> map, V defaultValue)
The value specified is returned when a missing key is found.
K - the key typeV - the value typemap - the map to decorate, must not be nulldefaultValue - the default value to return when the key is not foundIllegalArgumentException - if map is nullpublic static <K,V> DefaultedMap<K,V> defaultedMap(Map<K,V> map, Factory<? extends V> factory)
The factory specified is called when a missing key is found. The result will be returned as the result of the map get(key) method.
K - the key typeV - the value typemap - the map to decorate, must not be nullfactory - the factory to use to create entries, must not be nullIllegalArgumentException - if map or factory is nullpublic static <K,V> Map<K,V> defaultedMap(Map<K,V> map, Transformer<? super K,? extends V> transformer)
The transformer specified is called when a missing key is found. The key is passed to the transformer as the input, and the result will be returned as the result of the map get(key) method.
K - the key typeV - the value typemap - the map to decorate, must not be nulltransformer - the transformer to use as a factory to create entries, must not be nullIllegalArgumentException - if map or factory is nullCopyright © 2001–2013 The Apache Software Foundation. All rights reserved.