Package it.unimi.dsi.fastutil.objects

Class Reference2ObjectOpenHashMap<K,V>

java.lang.Object

it.unimi.dsi.fastutil.objects.AbstractReference2ObjectFunction<K,V>

it.unimi.dsi.fastutil.objects.AbstractReference2ObjectMap<K,V>

it.unimi.dsi.fastutil.objects.Reference2ObjectOpenHashMap<K,V>

All Implemented Interfaces:

Function<K,V>, Hash, Reference2ObjectFunction<K,V>, Reference2ObjectMap<K,V>, java.io.Serializable, java.lang.Cloneable, java.util.function.Function<K,V>, java.util.Map<K,V>

public class Reference2ObjectOpenHashMap<K,V>
extends AbstractReference2ObjectMap<K,V>
implements java.io.Serializable, java.lang.Cloneable, Hash

A type-specific hash map with a fast, small-footprint implementation.

Instances of this class use a hash table to represent a map. The table is filled up to a specified load factor, and then doubled in size to accommodate new entries. If the table is emptied below one fourth of the load factor, it is halved in size; however, the table is never reduced to a size smaller than that at creation time: this approach makes it possible to create maps with a large capacity in which insertions and deletions do not cause immediately rehashing. Moreover, halving is not performed when deleting entries from an iterator, as it would interfere with the iteration process.

Note that clear() does not modify the hash table size. Rather, a family of trimming methods lets you control the size of the table; this is particularly useful if you reuse instances of this class.

See Also:

Hash, HashCommon, Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class it.unimi.dsi.fastutil.objects.AbstractReference2ObjectMap

AbstractReference2ObjectMap.BasicEntry<K,V>, AbstractReference2ObjectMap.BasicEntrySet<K,V>

Nested classes/interfaces inherited from interface it.unimi.dsi.fastutil.Hash

Hash.Strategy<K>

Nested classes/interfaces inherited from interface it.unimi.dsi.fastutil.objects.Reference2ObjectMap

Reference2ObjectMap.Entry<K,V>, Reference2ObjectMap.FastEntrySet<K,V>

Field Summary

Fields inherited from interface it.unimi.dsi.fastutil.Hash

DEFAULT_GROWTH_FACTOR, DEFAULT_INITIAL_SIZE, DEFAULT_LOAD_FACTOR, FAST_LOAD_FACTOR, FREE, OCCUPIED, PRIMES, REMOVED, VERY_FAST_LOAD_FACTOR

Constructor Summary

Constructors

Constructor	Description
Reference2ObjectOpenHashMap()	Creates a new hash map with initial expected Hash.DEFAULT_INITIAL_SIZE entries and Hash.DEFAULT_LOAD_FACTOR as load factor.
Reference2ObjectOpenHashMap(int expected)	Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor.
Reference2ObjectOpenHashMap(int expected, float f)	Creates a new hash map.
Reference2ObjectOpenHashMap(Reference2ObjectMap<K,V> m)	Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific one.
Reference2ObjectOpenHashMap(Reference2ObjectMap<K,V> m, float f)	Creates a new hash map copying a given type-specific one.
Reference2ObjectOpenHashMap(java.util.Map<? extends K,? extends V> m)	Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given one.
Reference2ObjectOpenHashMap(java.util.Map<? extends K,? extends V> m, float f)	Creates a new hash map copying a given one.
Reference2ObjectOpenHashMap(K[] k, V[] v)	Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor using the elements of two parallel arrays.
Reference2ObjectOpenHashMap(K[] k, V[] v, float f)	Creates a new hash map using the elements of two parallel arrays.

Method Summary

Modifier and Type	Method	Description
void	clear()	Removes all of the mappings from this map (optional operation).
Reference2ObjectOpenHashMap<K,V>	clone()	Returns a deep copy of this map.
boolean	containsKey(java.lang.Object k)	Returns true if this function contains a mapping for the specified key.
boolean	containsValue(java.lang.Object v)
V	get(java.lang.Object k)	Returns the value to which the given key is mapped.
int	hashCode()	Returns a hash code for this map.
boolean	isEmpty()
ReferenceSet<K>	keySet()	Returns a type-specific-set view of the keys of this map.
V	put(K k, V v)	Adds a pair to the map (optional operation).
void	putAll(java.util.Map<? extends K,? extends V> m)
Reference2ObjectMap.FastEntrySet<K,V>	reference2ObjectEntrySet()	Returns a type-specific set view of the mappings contained in this map.
V	remove(java.lang.Object k)	Removes the mapping with the given key (optional operation).
int	size()	Returns the number of key/value mappings in this map.
boolean	trim()	Rehashes the map, making the table as small as possible.
boolean	trim(int n)	Rehashes this map if the table is too large.
ObjectCollection<V>	values()	Returns a type-specific-set view of the values of this map.

Methods inherited from class it.unimi.dsi.fastutil.objects.AbstractReference2ObjectFunction

defaultReturnValue, defaultReturnValue

Methods inherited from class it.unimi.dsi.fastutil.objects.AbstractReference2ObjectMap

equals, toString

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

compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface it.unimi.dsi.fastutil.objects.Reference2ObjectMap

defaultReturnValue, defaultReturnValue, entrySet

Constructor Detail

Reference2ObjectOpenHashMap

public Reference2ObjectOpenHashMap(int expected,
                                   float f)

Creates a new hash map.

The actual table size will be the least power of two greater than expected/f.

Parameters:

expected - the expected number of elements in the hash map.

f - the load factor.

Reference2ObjectOpenHashMap

public Reference2ObjectOpenHashMap(int expected)

Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor.

Parameters:

expected - the expected number of elements in the hash map.

Reference2ObjectOpenHashMap

public Reference2ObjectOpenHashMap()

Creates a new hash map with initial expected Hash.DEFAULT_INITIAL_SIZE entries and Hash.DEFAULT_LOAD_FACTOR as load factor.

Reference2ObjectOpenHashMap

public Reference2ObjectOpenHashMap(java.util.Map<? extends K,? extends V> m,
                                   float f)

Creates a new hash map copying a given one.

Parameters:

m - a Map to be copied into the new hash map.

f - the load factor.

Reference2ObjectOpenHashMap

public Reference2ObjectOpenHashMap(java.util.Map<? extends K,? extends V> m)

Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given one.

Parameters:

m - a Map to be copied into the new hash map.

Reference2ObjectOpenHashMap

public Reference2ObjectOpenHashMap(Reference2ObjectMap<K,V> m,
                                   float f)

Creates a new hash map copying a given type-specific one.

Parameters:

m - a type-specific map to be copied into the new hash map.

f - the load factor.

Reference2ObjectOpenHashMap

public Reference2ObjectOpenHashMap(Reference2ObjectMap<K,V> m)

Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific one.

Parameters:

m - a type-specific map to be copied into the new hash map.

Reference2ObjectOpenHashMap

public Reference2ObjectOpenHashMap(K[] k,
                                   V[] v,
                                   float f)

Creates a new hash map using the elements of two parallel arrays.

Parameters:

k - the array of keys of the new hash map.

v - the array of corresponding values in the new hash map.

f - the load factor.

Throws:

java.lang.IllegalArgumentException - if k and v have different lengths.

Reference2ObjectOpenHashMap

public Reference2ObjectOpenHashMap(K[] k,
                                   V[] v)

Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor using the elements of two parallel arrays.

Parameters:

k - the array of keys of the new hash map.

v - the array of corresponding values in the new hash map.

Throws:

java.lang.IllegalArgumentException - if k and v have different lengths.

Method Detail

putAll

public void putAll(java.util.Map<? extends K,? extends V> m)

Description copied from class: AbstractReference2ObjectMap

Specified by:

putAll in interface java.util.Map<K,V>

Overrides:

putAll in class AbstractReference2ObjectMap<K,V>

put

public V put(K k,
             V v)

Description copied from interface: Reference2ObjectMap

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 java.util.Map<K,V>

Specified by:

put in interface Reference2ObjectFunction<K,V>

Specified by:

put in interface Reference2ObjectMap<K,V>

Parameters:

k - the key.

v - 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

public V remove(java.lang.Object k)

Description copied from interface: Reference2ObjectMap

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 java.util.Map<K,V>

Specified by:

remove in interface Reference2ObjectFunction<K,V>

Specified by:

remove in interface Reference2ObjectMap<K,V>

Parameters:

k - 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)

get

public V get(java.lang.Object k)

Description copied from interface: Reference2ObjectFunction

Returns the value to which the given key is mapped.

Specified by:

get in interface Function<K,V>

Specified by:

get in interface java.util.Map<K,V>

Specified by:

get in interface Reference2ObjectFunction<K,V>

Parameters:

k - 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)

containsKey

public boolean containsKey(java.lang.Object k)

Description copied from interface: Reference2ObjectMap

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 java.util.Map<K,V>

Specified by:

containsKey in interface Reference2ObjectMap<K,V>

Overrides:

containsKey in class AbstractReference2ObjectMap<K,V>

Parameters:

k - the key.

Returns:

true if this function associates a value to key.

See Also:

Map.containsKey(Object)

containsValue

public boolean containsValue(java.lang.Object v)

Specified by:

containsValue in interface java.util.Map<K,V>

Overrides:

containsValue in class AbstractReference2ObjectMap<K,V>

clear

public void clear()

Description copied from interface: Reference2ObjectMap

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 java.util.Map<K,V>

Specified by:

clear in interface Reference2ObjectMap<K,V>

See Also:

Map.clear()

size

public int size()

Description copied from interface: Reference2ObjectMap

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 java.util.Map<K,V>

Specified by:

size in interface Reference2ObjectMap<K,V>

Returns:

the number of key-value mappings in this map.

See Also:

Size64

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface java.util.Map<K,V>

Overrides:

isEmpty in class AbstractReference2ObjectMap<K,V>

reference2ObjectEntrySet

public Reference2ObjectMap.FastEntrySet<K,V> reference2ObjectEntrySet()

Description copied from interface: Reference2ObjectMap

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).

Specified by:

reference2ObjectEntrySet in interface Reference2ObjectMap<K,V>

Returns:

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

See Also:

Map.entrySet()

keySet

public ReferenceSet<K> keySet()

Description copied from class: AbstractReference2ObjectMap

Returns a type-specific-set view of the keys of this map.

The view is backed by the set returned by Map.entrySet(). Note that no attempt is made at caching the result of this method, as this would require adding some attributes that lightweight implementations would not need. Subclasses may easily override this policy by calling this method and caching the result, but implementors are encouraged to write more efficient ad-hoc implementations.

Specified by:

keySet in interface java.util.Map<K,V>

Specified by:

keySet in interface Reference2ObjectMap<K,V>

Overrides:

keySet in class AbstractReference2ObjectMap<K,V>

Returns:

a set view of the keys of this map; it may be safely cast to a type-specific interface.

See Also:

Map.keySet()

values

public ObjectCollection<V> values()

Description copied from class: AbstractReference2ObjectMap

Returns a type-specific-set view of the values of this map.

The view is backed by the set returned by Map.entrySet(). Note that no attempt is made at caching the result of this method, as this would require adding some attributes that lightweight implementations would not need. Subclasses may easily override this policy by calling this method and caching the result, but implementors are encouraged to write more efficient ad-hoc implementations.

Specified by:

values in interface java.util.Map<K,V>

Specified by:

values in interface Reference2ObjectMap<K,V>

Overrides:

values in class AbstractReference2ObjectMap<K,V>

Returns:

a set view of the values of this map; it may be safely cast to a type-specific interface.

See Also:

Map.values()

trim

public boolean trim()

Rehashes the map, making the table as small as possible.

This method rehashes the table to the smallest size satisfying the load factor. It can be used when the set will not be changed anymore, so to optimize access speed and size.

If the table size is already the minimum possible, this method does nothing.

Returns:

true if there was enough memory to trim the map.

See Also:

trim(int)

trim

public boolean trim(int n)

Rehashes this map if the table is too large.

Let N be the smallest table size that can hold max(n,size()) entries, still satisfying the load factor. If the current table size is smaller than or equal to N, this method does nothing. Otherwise, it rehashes this map in a table of size N.

This method is useful when reusing maps. Clearing a map leaves the table size untouched. If you are reusing a map many times, you can call this method with a typical size to avoid keeping around a very large table just because of a few large transient maps.

Parameters:

n - the threshold for the trimming.

Returns:

true if there was enough memory to trim the map.

See Also:

trim()

clone

public Reference2ObjectOpenHashMap<K,V> clone()

Returns a deep copy of this map.

This method performs a deep copy of this hash map; the data stored in the map, however, is not cloned. Note that this makes a difference only for object keys.

Returns:

a deep copy of this map.

hashCode

public int hashCode()

Returns a hash code for this map. This method overrides the generic method provided by the superclass. Since equals() is not overriden, it is important that the value returned by this method is the same value as the one returned by the overriden method.

Specified by:

hashCode in interface java.util.Map<K,V>

Overrides:

hashCode in class AbstractReference2ObjectMap<K,V>

Returns:

a hash code for this map.