Package it.unimi.dsi.fastutil.objects

Interface Reference2ReferenceFunction<K,​V>

All Superinterfaces:
Function<K,​V>, Function<K,​V>
All Known Subinterfaces:
Reference2ReferenceMap<K,​V>, Reference2ReferenceSortedMap<K,​V>
All Known Implementing Classes:
AbstractReference2ReferenceFunction, AbstractReference2ReferenceMap, AbstractReference2ReferenceSortedMap, Reference2ReferenceArrayMap, Reference2ReferenceFunctions.EmptyFunction, Reference2ReferenceFunctions.Singleton, Reference2ReferenceFunctions.SynchronizedFunction, Reference2ReferenceFunctions.UnmodifiableFunction, Reference2ReferenceLinkedOpenHashMap, Reference2ReferenceMaps.EmptyMap, Reference2ReferenceMaps.Singleton, Reference2ReferenceMaps.SynchronizedMap, Reference2ReferenceMaps.UnmodifiableMap, Reference2ReferenceOpenCustomHashMap, Reference2ReferenceOpenHashMap, Reference2ReferenceSortedMaps.EmptySortedMap, Reference2ReferenceSortedMaps.Singleton, Reference2ReferenceSortedMaps.SynchronizedSortedMap, Reference2ReferenceSortedMaps.UnmodifiableSortedMap
Functional Interface:
This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
@FunctionalInterface
public interface Reference2ReferenceFunction<K,​V>
extends Function<K,​V>
A type-specific Function; provides some additional methods that use polymorphism to avoid (un)boxing.

Type-specific versions of get(), put() and remove() cannot rely on null to denote absence of a key. Rather, they return a default return value, which is set to 0/false at creation, but can be changed using the defaultReturnValue() method.

For uniformity reasons, even functions returning objects implement the default return value (of course, in this case the default return value is initialized to null).

The default implementation of optional operations just throw an UnsupportedOperationException, except for the type-specific containsKey(), which return true. Generic versions of accessors delegate to the corresponding type-specific counterparts following the interface rules.

Warning: to fall in line as much as possible with the standard map interface, it is required that standard versions of get(), put() and remove() for maps with primitive-type keys or values return null to denote missing keys rather than wrap the default return value in an object. In case both keys and values are reference types, the default return value must be returned instead, thus violating the standard map interface when the default return value is not null.

See Also:
Function

  • Method Summary

    Modifier and Type Method Description
    default V defaultReturnValue()
    Gets the default return value.
    default void defaultReturnValue​(V rv)
    Sets the default return value (optional operation).
    V get​(Object key)
    Returns the value to which the given key is mapped.
    default V put​(K key, V value)
    Adds a pair to the map (optional operation).
    default V remove​(Object key)
    Removes the mapping with the given key (optional operation).

    Methods inherited from interface it.unimi.dsi.fastutil.Function

    apply, clear, containsKey, size

    Methods inherited from interface java.util.function.Function

    andThen, compose

  • Method Details

    • put

      default V put​(K key, V value)
      Adds a pair to the map (optional operation).
      Specified by:
      put in interface Function<K,​V>
      Parameters:
      key - the key.
      value - the value.
      Returns:
      the old value, or the default return value if no value was present for the given key.
      See Also:
      Function.put(Object,Object)

    • get

      V get​(Object key)
      Returns the value to which the given key is mapped.
      Specified by:
      get in interface Function<K,​V>
      Parameters:
      key - the key.
      Returns:
      the corresponding value, or the default return value if no value was present for the given key.
      See Also:
      Function.get(Object)

    • remove

      default V remove​(Object key)
      Removes the mapping with the given key (optional operation).
      Specified by:
      remove in interface Function<K,​V>
      Parameters:
      key - the key.
      Returns:
      the old value, or the default return value if no value was present for the given key.
      See Also:
      Function.remove(Object)

    • defaultReturnValue

      default void defaultReturnValue​(V rv)
      Sets the default return value (optional operation). This value must be returned by type-specific versions of get(), put() and remove() to denote that the map does not contain the specified key. It must be 0/false/null by default.
      Parameters:
      rv - the new default return value.
      See Also:
      defaultReturnValue()

    • defaultReturnValue

      default V defaultReturnValue()
      Gets the default return value.

      This default implementation just return the default null value of the type (null for objects, 0 for scalars, false for Booleans).

      Returns:
      the current default return value.