de.unkrig.commons.lang.protocol
Class Mapping<K,V>

java.lang.Object
  de.unkrig.commons.lang.protocol.Mapping<K,V>

Type Parameters:

K - The 'key' type

V - The 'value' type

public abstract class Mapping<K,V>
extends java.lang.Object

A map that computes a value only when get(Object) is invoked. Consequently, in contrast with Map, it has no specific size, and thus no Map.entrySet(), Map.keySet() and Map.values() set. Also the modifying operations (Map.put(Object, Object), Map.putAll(Map), Map.remove(Object), Map.clear()) are all missing, because a Mapping is not changed by 'putting' key-value-pairs into it.

Actually Map should extend Mapping, but it doesn't - thus there are the asMap() and Mappings.fromMap(Map) helpers.

The relationship between Mapping and Map is very much like that between Predicate and Collection.

Constructor Summary

Mapping()

Method Summary

java.util.Map<K,V>	asMap() Returns a proxy Map for a Mapping where all methods declared by Map but not by Mapping throw an UnsupportedOperationException.
abstract boolean	containsKey(java.lang.Object key)
abstract V	get(java.lang.Object key)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Mapping

public Mapping()

Method Detail

containsKey

public abstract boolean containsKey(@Nullable
                                    java.lang.Object key)

See Also:

Map.containsKey(Object)

get

@Nullable
public abstract V get(@Nullable
                               java.lang.Object key)

See Also:

Map.get(Object)

asMap

public final java.util.Map<K,V> asMap()

Returns a proxy Map for a Mapping where all methods declared by Map but not by Mapping throw an UnsupportedOperationException.