Package it.unimi.dsi.fastutil.objects

Interface Object2ReferenceMap<K,V>

All Superinterfaces:

Function<K,V>, Function<K,V>, Map<K,V>, Object2ReferenceFunction<K,V>

All Known Subinterfaces:

Object2ReferenceSortedMap<K,V>

All Known Implementing Classes:

AbstractObject2ReferenceMap, AbstractObject2ReferenceSortedMap, Object2ReferenceArrayMap, Object2ReferenceAVLTreeMap, Object2ReferenceLinkedOpenCustomHashMap, Object2ReferenceLinkedOpenHashMap, Object2ReferenceMaps.EmptyMap, Object2ReferenceMaps.Singleton, Object2ReferenceMaps.SynchronizedMap, Object2ReferenceMaps.UnmodifiableMap, Object2ReferenceOpenCustomHashMap, Object2ReferenceOpenHashMap, Object2ReferenceRBTreeMap, Object2ReferenceSortedMaps.EmptySortedMap, Object2ReferenceSortedMaps.Singleton, Object2ReferenceSortedMaps.SynchronizedSortedMap, Object2ReferenceSortedMaps.UnmodifiableSortedMap

public interface Object2ReferenceMap<K,V>
extends Object2ReferenceFunction<K,V>, Map<K,V>

A type-specific Map; provides some additional methods that use polymorphism to avoid (un)boxing, and handling of a default return value.

Besides extending the corresponding type-specific function, this interface strengthens Map.entrySet(), keySet() and values(). Moreover, a number of methods, such as size(), defaultReturnValue(), etc., are un-defaulted as their function default do not make sense for a map. Maps returning entry sets of type Object2ReferenceMap.FastEntrySet support also fast iteration.

This interface specifies reference equality semantics (members will be compared equal with == instead of equals) for its keys or values (or both), which may result in breaks in contract if attempted to be used with non reference-equality semantics based Maps. For example, a aReferenceToIntMap.equals(aObjectToIntMap) may return different a different result then aObjectToIntMap.equals(aReferenceToIntMap), in violation of equals's contract requiring it being symmetric.

A submap or subset may or may not have an independent default return value (which however must be initialized to the default return value of the originator).

See Also:

• Map

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	Object2ReferenceMap.Entry<K,V>	A type-specific Map.Entry; provides some additional methods that use polymorphism to avoid (un)boxing.
static interface	Object2ReferenceMap.FastEntrySet<K,V>	An entry set providing fast iteration.

Method Summary

Modifier and Type	Method	Description
default void	clear()	Removes all of the mappings from this map (optional operation).
default V	compute(K key, BiFunction<? super K,? super V,? extends V> remappingFunction)	Attempts to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping).
default V	computeIfAbsent(K key, Object2ReferenceFunction<? super K,? extends V> mappingFunction)	If the specified key is not already associated with a value, attempts to compute its value using the given mapping function and enters it into this map, unless the key is not present in the given mapping function.
default V	computeIfPresent(K key, BiFunction<? super K,? super V,? extends V> remappingFunction)	If the value for the specified key is present, attempts to compute a new mapping given the key and its current mapped value.
default V	computeReferenceIfAbsentPartial(K key, Object2ReferenceFunction<? super K,? extends V> mappingFunction)	Deprecated. Please use computeIfAbsent() instead.
boolean	containsKey(Object key)	Returns true if this function contains a mapping for the specified key.
V	defaultReturnValue()	Gets the default return value.
void	defaultReturnValue(V rv)	Sets the default return value (optional operation).
default ObjectSet<Map.Entry<K,V>>	entrySet()	Returns a set view of the mappings contained in this map.
default void	forEach(BiConsumer<? super K,? super V> consumer)
default V	getOrDefault(Object key, V defaultValue)	Returns the value to which the specified key is mapped, or the defaultValue if this map contains no mapping for the key.
ObjectSet<K>	keySet()
default V	merge(K key, V value, BiFunction<? super V,? super V,? extends V> remappingFunction)	If the specified key is not already associated with a value, associates it with the given value.
ObjectSet<Object2ReferenceMap.Entry<K,V>>	object2ReferenceEntrySet()	Returns a type-specific set view of the mappings contained in this map.
default V	put(K key, V value)	Adds a pair to the map (optional operation).
default V	putIfAbsent(K key, V value)	If the specified key is not already associated with a value, associates it with the given value and returns the default return value, else returns the current value.
default V	remove(Object key)	Removes the mapping with the given key (optional operation).
default boolean	remove(Object key, Object value)	Removes the entry for the specified key only if it is currently mapped to the specified value.
default V	replace(K key, V value)	Replaces the entry for the specified key only if it is currently mapped to some value.
default boolean	replace(K key, V oldValue, V newValue)	Replaces the entry for the specified key only if currently mapped to the specified value.
int	size()	Returns the number of key/value mappings in this map.
ReferenceCollection<V>	values()

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

apply

Methods inherited from interface java.util.function.Function

andThen, compose

Methods inherited from interface java.util.Map

computeIfAbsent, containsValue, equals, get, hashCode, isEmpty, putAll, replaceAll

Methods inherited from interface it.unimi.dsi.fastutil.objects.Object2ReferenceFunction

andThenByte, andThenChar, andThenDouble, andThenFloat, andThenInt, andThenLong, andThenObject, andThenReference, andThenShort, composeByte, composeChar, composeDouble, composeFloat, composeInt, composeLong, composeObject, composeReference, composeShort, get

Method Details

size

int size()

Returns the number of key/value mappings in this map. If the map contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

Specified by:

size in interface Function<K,V>

Specified by:

size in interface Map<K,V>

Returns:

the number of key-value mappings in this map.

See Also:

• Size64

clear

default void clear()

Removes all of the mappings from this map (optional operation). The map will be empty after this call returns.

Specified by:

clear in interface Function<K,V>

Specified by:

clear in interface Map<K,V>

Throws:

UnsupportedOperationException - if the clear() operation is not supported by this map

See Also:

• Map.clear()

defaultReturnValue

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 null by default.

Warning: Changing this to a non-null value can have unforeseen consequences. Especially, it breaks compatibility with the specifications of Java's Map interface. It has to be used with great care and thorough study of all method comments is recommended.

Specified by:

defaultReturnValue in interface Object2ReferenceFunction<K,V>

Parameters:

rv - the new default return value.

See Also:

• defaultReturnValue()

defaultReturnValue

V defaultReturnValue()

Gets the default return value.

Specified by:

defaultReturnValue in interface Object2ReferenceFunction<K,V>

Returns:

the current default return value.

object2ReferenceEntrySet

ObjectSet<Object2ReferenceMap.Entry<K,V>> object2ReferenceEntrySet()

Returns a type-specific set view of the mappings contained in this map.

This method is necessary because there is no inheritance along type parameters: it is thus impossible to strengthen Map.entrySet() so that it returns an ObjectSet of type-specific entries (the latter makes it possible to access keys and values with type-specific methods).

Returns:

a type-specific set view of the mappings contained in this map.

See Also:

• Map.entrySet()

entrySet

default ObjectSet<Map.Entry<K,V>> entrySet()

Returns a set view of the mappings contained in this map.

Specified by:

entrySet in interface Map<K,V>

Returns:

a set view of the mappings contained in this map.

See Also:

• Map.entrySet()

API Notes:

Note that this specification strengthens the one given in Map.entrySet().

put

default V put(K key,
 V value)

Adds a pair to the map (optional operation).

This default implementation just delegates to the corresponding function method.

Specified by:

put in interface Function<K,V>

Specified by:

put in interface Map<K,V>

Specified by:

put in interface Object2ReferenceFunction<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)

remove

default V remove(Object key)

Removes the mapping with the given key (optional operation).

This default implementation just delegates to the corresponding type-specific–function method.

Specified by:

remove in interface Function<K,V>

Specified by:

remove in interface Map<K,V>

Specified by:

remove in interface Object2ReferenceFunction<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)

keySet

ObjectSet<K> keySet()

Specified by:

keySet in interface Map<K,V>

Returns:

a set view of the keys contained in this map.

See Also:

• Map.keySet()

API Notes:

Note that this specification strengthens the one given in Map.keySet().

values

ReferenceCollection<V> values()

Specified by:

values in interface Map<K,V>

Returns:

a set view of the values contained in this map.

See Also:

• Map.values()

API Notes:

Note that this specification strengthens the one given in Map.values().

containsKey

boolean containsKey(Object key)

Returns true if this function contains a mapping for the specified key.

Specified by:

containsKey in interface Function<K,V>

Specified by:

containsKey in interface Map<K,V>

Parameters:

key - the key.

Returns:

true if this function associates a value to key.

See Also:

• Map.containsKey(Object)

forEach

default void forEach(BiConsumer<? super K,? super V> consumer)

Specified by:

forEach in interface Map<K,V>

getOrDefault

default V getOrDefault(Object key,
 V defaultValue)

Returns the value to which the specified key is mapped, or the defaultValue if this map contains no mapping for the key.

Specified by:

getOrDefault in interface Function<K,V>

Specified by:

getOrDefault in interface Map<K,V>

Specified by:

getOrDefault in interface Object2ReferenceFunction<K,V>

Parameters:

key - the key.

defaultValue - the default mapping of the key.

Returns:

the value to which the specified key is mapped, or the defaultValue if this map contains no mapping for the key.

Since:

8.0.0

See Also:

• Map.getOrDefault(Object, Object)

putIfAbsent

default V putIfAbsent(K key,
 V value)

If the specified key is not already associated with a value, associates it with the given value and returns the default return value, else returns the current value.

Specified by:

putIfAbsent in interface Map<K,V>

Parameters:

key - key with which the specified value is to be associated.

value - value to be associated with the specified key.

Returns:

the previous value associated with the specified key, or the default return value if there was no mapping for the key.

Since:

8.0.0

See Also:

• Map.putIfAbsent(Object, Object)

remove

default boolean remove(Object key,
 Object value)

Removes the entry for the specified key only if it is currently mapped to the specified value.

Specified by:

remove in interface Map<K,V>

Parameters:

key - key with which the specified value is associated.

value - value expected to be associated with the specified key.

Returns:

true if the value was removed.

Since:

8.0.0

See Also:

• Map.remove(Object, Object)

replace

default boolean replace(K key,
 V oldValue,
 V newValue)

Replaces the entry for the specified key only if currently mapped to the specified value.

Specified by:

replace in interface Map<K,V>

Parameters:

key - key with which the specified value is associated.

oldValue - value expected to be associated with the specified key.

newValue - value to be associated with the specified key.

Returns:

true if the value was replaced.

Since:

8.0.0

See Also:

• Map.replace(Object, Object, Object)

replace

default V replace(K key,
 V value)

Replaces the entry for the specified key only if it is currently mapped to some value.

Specified by:

replace in interface Map<K,V>

Parameters:

key - key with which the specified value is associated.

value - value to be associated with the specified key.

Returns:

the previous value associated with the specified key, or the default return value if there was no mapping for the key.

Since:

8.0.0

See Also:

• Map.replace(Object, Object)

computeIfAbsent

default V computeIfAbsent(K key,
 Object2ReferenceFunction<? super K,? extends V> mappingFunction)

If the specified key is not already associated with a value, attempts to compute its value using the given mapping function and enters it into this map, unless the key is not present in the given mapping function.

This version of computeIfAbsent() uses a type-specific version of fastutil's Function. Since Function has a containsKey() method, it is possible to avoid adding a key by having containsKey() return false for that key.

Parameters:

key - key with which the specified value is to be associated.

mappingFunction - the function to compute a value.

Returns:

the current (existing or computed) value associated with the specified key.

Since:

8.0.0

See Also:

• Map.computeIfAbsent(Object, java.util.function.Function)

API Notes:

all computeIfAbsent() methods have a different logic based on the argument; no delegation is performed, contrarily to other superficially similar methods such as Iterator.forEachRemaining(java.util.function.Consumer<? super E>) or List.replaceAll(java.util.function.UnaryOperator<E>).

computeReferenceIfAbsentPartial

@Deprecated
default V computeReferenceIfAbsentPartial(K key,
 Object2ReferenceFunction<? super K,? extends V> mappingFunction)

Deprecated.

Please use computeIfAbsent() instead.

computeIfPresent

default V computeIfPresent(K key,
 BiFunction<? super K,? super V,? extends V> remappingFunction)

If the value for the specified key is present, attempts to compute a new mapping given the key and its current mapped value.

Specified by:

computeIfPresent in interface Map<K,V>

Parameters:

key - key with which the specified value is to be associated.

remappingFunction - the function to compute a value.

Returns:

the new value associated with the specified key, or the default return value if none.

Since:

8.0.0

See Also:

• Map.computeIfPresent(Object, java.util.function.BiFunction)

API Notes:

The JDK specification for this method equates not being associated with a value with being associated with {code null}. This is not the case for this method.

compute

default V compute(K key,
 BiFunction<? super K,? super V,? extends V> remappingFunction)

Attempts to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping).

If the function returns null, the mapping is removed (or remains absent if initially absent). If the function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.

Specified by:

compute in interface Map<K,V>

Parameters:

key - key with which the specified value is to be associated.

remappingFunction - the function to compute a value.

Returns:

the new value associated with the specified key, or the default return value if none.

Since:

8.0.0

See Also:

• Map.compute(Object, java.util.function.BiFunction)

merge

default V merge(K key,
 V value,
 BiFunction<? super V,? super V,? extends V> remappingFunction)

If the specified key is not already associated with a value, associates it with the given value. Otherwise, replaces the associated value with the results of the given remapping function, or removes if the result is null.

Specified by:

merge in interface Map<K,V>

Parameters:

key - key with which the resulting value is to be associated.

value - the value to be merged with the existing value associated with the key or, if no existing value is associated with the key, to be associated with the key.

remappingFunction - the function to recompute a value if present.

Returns:

the new value associated with the specified key, or the default return value if no value is associated with the key.

Since:

8.0.0

See Also:

• Map.merge(Object, Object, java.util.function.BiFunction)

API Notes:

The JDK specification for this method equates not being associated with a value with being associated with {code null}. This is not the case for this method.