it.unimi.dsi.fastutil.objects
Class Reference2ReferenceOpenHashMap<K,V>

java.lang.Object
  it.unimi.dsi.fastutil.objects.AbstractReference2ReferenceFunction<K,V>
      it.unimi.dsi.fastutil.objects.AbstractReference2ReferenceMap<K,V>
          it.unimi.dsi.fastutil.objects.Reference2ReferenceOpenHashMap<K,V>

All Implemented Interfaces:

Function<K,V>, Hash, Reference2ReferenceFunction<K,V>, Reference2ReferenceMap<K,V>, Serializable, Cloneable, Map<K,V>

public class Reference2ReferenceOpenHashMap<K,V>
extends AbstractReference2ReferenceMap<K,V>
implements Serializable, 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 enlarged as needed when new entries are created, but it is never made smaller (even on a clear()). A family of trimming methods lets you control the size of the table; this is particularly useful if you reuse instances of this class.

The enlargement speed is controlled by the growth factor, a positive number. If the growth factor is p, then the table is enlarged each time roughly by a factor 2^p/16. By default, p is Hash.DEFAULT_GROWTH_FACTOR, which means that the table is doubled at each enlargement, but one can easily set more or less aggressive policies by calling growthFactor(int) (note that the growth factor is not serialized: deserialized tables gets the default growth factor).

See Also:

Hash, HashCommon, Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class it.unimi.dsi.fastutil.objects.AbstractReference2ReferenceMap

AbstractReference2ReferenceMap.BasicEntry<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.Reference2ReferenceMap

Reference2ReferenceMap.Entry<K,V>, Reference2ReferenceMap.FastEntrySet<K,V>

Field Summary

static long

serialVersionUID

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

Reference2ReferenceOpenHashMap()
Creates a new hash map with Hash.DEFAULT_INITIAL_SIZE entries and Hash.DEFAULT_LOAD_FACTOR as load factor.

Reference2ReferenceOpenHashMap(int n)
Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor.

Reference2ReferenceOpenHashMap(int n, float f)
Creates a new hash map.

Reference2ReferenceOpenHashMap(K[] k, V[] v)
Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor using the elements of two parallel arrays.

Reference2ReferenceOpenHashMap(K[] k, V[] v, float f)
Creates a new hash map using the elements of two parallel arrays.

Reference2ReferenceOpenHashMap(Map<? extends K,? extends V> m)
Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given one.

Reference2ReferenceOpenHashMap(Map<? extends K,? extends V> m, float f)
Creates a new hash map copying a given one.

Reference2ReferenceOpenHashMap(Reference2ReferenceMap<K,V> m)
Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific one.

Reference2ReferenceOpenHashMap(Reference2ReferenceMap<K,V> m, float f)
Creates a new hash map copying a given type-specific one.

Method Summary

void	clear() Removes all associations from this function (optional operation).
Object	clone() Returns a deep copy of this map.
boolean	containsKey(Object k) Checks whether the given value is contained in AbstractReference2ReferenceMap.keySet().
boolean	containsValue(Object v) Checks whether the given value is contained in AbstractReference2ReferenceMap.values().
V	get(Object k) Returns the value associated by this function to the specified key.
int	growthFactor() Gets the growth factor.
void	growthFactor(int growthFactor) Sets the growth factor.
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) Associates the specified value with the specified key in this function (optional operation).
Reference2ReferenceMap.FastEntrySet<K,V>	reference2ReferenceEntrySet() Returns a type-specific set view of the mappings contained in this map.
boolean	rehash() Rehashes this map without changing the table size.
V	remove(Object k) Removes this key and the associated value from this function if it is present (optional operation).
int	size() Returns the intended number of keys in this function, or -1 if no such number exists.
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.
ReferenceCollection<V>	values() Returns a type-specific-set view of the values of this map.

Methods inherited from class it.unimi.dsi.fastutil.objects.AbstractReference2ReferenceMap

entrySet, equals, putAll, toString

Methods inherited from class it.unimi.dsi.fastutil.objects.AbstractReference2ReferenceFunction

defaultReturnValue, defaultReturnValue

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface it.unimi.dsi.fastutil.objects.Reference2ReferenceFunction

defaultReturnValue, defaultReturnValue

Field Detail

serialVersionUID

public static final long serialVersionUID

See Also:

Constant Field Values

Constructor Detail

Reference2ReferenceOpenHashMap

public Reference2ReferenceOpenHashMap(int n,
                                      float f)

Creates a new hash map. The actual table size is the least available prime greater than n/f.

Parameters:

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

f - the load factor.

See Also:

Hash.PRIMES

Reference2ReferenceOpenHashMap

public Reference2ReferenceOpenHashMap(int n)

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

Parameters:

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

Reference2ReferenceOpenHashMap

public Reference2ReferenceOpenHashMap()

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

Reference2ReferenceOpenHashMap

public Reference2ReferenceOpenHashMap(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.

Reference2ReferenceOpenHashMap

public Reference2ReferenceOpenHashMap(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.

Reference2ReferenceOpenHashMap

public Reference2ReferenceOpenHashMap(Reference2ReferenceMap<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.

Reference2ReferenceOpenHashMap

public Reference2ReferenceOpenHashMap(Reference2ReferenceMap<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.

Reference2ReferenceOpenHashMap

public Reference2ReferenceOpenHashMap(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:

IllegalArgumentException - if k and v have different lengths.

Reference2ReferenceOpenHashMap

public Reference2ReferenceOpenHashMap(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:

IllegalArgumentException - if k and v have different lengths.

Method Detail

growthFactor

public void growthFactor(int growthFactor)

Sets the growth factor. Subsequent enlargements will increase the table size roughly by a multiplicative factor of 2^p/16.

Parameters:

growthFactor - the new growth factor; it must be positive.

growthFactor

public int growthFactor()

Gets the growth factor.

Returns:

the growth factor of this set.

See Also:

growthFactor(int)

put

public V put(K k,
             V v)

Description copied from interface: Function

Associates the specified value with the specified key in this function (optional operation).

Specified by:

put in interface Function<K,V>

Specified by:

put in interface Map<K,V>

Overrides:

put in class AbstractReference2ReferenceFunction<K,V>

Parameters:

k - the key.

v - the value.

Returns:

the old value, or null if no value was present for the given key.

See Also:

Map.put(Object,Object)

containsValue

public boolean containsValue(Object v)

Description copied from class: AbstractReference2ReferenceMap

Checks whether the given value is contained in AbstractReference2ReferenceMap.values().

Specified by:

containsValue in interface Map<K,V>

Overrides:

containsValue in class AbstractReference2ReferenceMap<K,V>

clear

public void clear()

Description copied from interface: Function

Removes all associations from this function (optional operation).

Specified by:

clear in interface Function<K,V>

Specified by:

clear in interface Map<K,V>

Overrides:

clear in class AbstractReference2ReferenceFunction<K,V>

See Also:

Map.clear()

containsKey

public boolean containsKey(Object k)

Description copied from class: AbstractReference2ReferenceMap

Checks whether the given value is contained in AbstractReference2ReferenceMap.keySet().

Specified by:

containsKey in interface Function<K,V>

Specified by:

containsKey in interface Map<K,V>

Overrides:

containsKey in class AbstractReference2ReferenceMap<K,V>

Parameters:

k - the key.

Returns:

true if this function associates a value to key.

See Also:

Map.containsKey(Object)

size

public int size()

Description copied from interface: Function

Returns the intended number of keys in this function, or -1 if no such number exists.

Most function implementations will have some knowledge of the intended number of keys in their domain. In some cases, however, this might not be possible.

Specified by:

size in interface Function<K,V>

Specified by:

size in interface Map<K,V>

Returns:

the intended number of keys in this function, or -1 if that number is not available.

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Map<K,V>

Overrides:

isEmpty in class AbstractReference2ReferenceMap<K,V>

get

public V get(Object k)

Description copied from interface: Function

Returns the value associated by this function to the specified key.

Specified by:

get in interface Function<K,V>

Specified by:

get in interface Map<K,V>

Parameters:

k - the key.

Returns:

the corresponding value, or null if no value was present for the given key.

See Also:

Map.get(Object)

remove

public V remove(Object k)

Description copied from interface: Function

Removes this key and the associated value from this function if it is present (optional operation).

Specified by:

remove in interface Function<K,V>

Specified by:

remove in interface Map<K,V>

Overrides:

remove in class AbstractReference2ReferenceFunction<K,V>

Returns:

the old value, or null if no value was present for the given key.

See Also:

Map.remove(Object)

reference2ReferenceEntrySet

public Reference2ReferenceMap.FastEntrySet<K,V> reference2ReferenceEntrySet()

Description copied from interface: Reference2ReferenceMap

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 Reference2ReferenceMap.entrySet() so that it returns an ObjectSet of objects of type Reference2ReferenceMap.Entry (the latter makes it possible to access keys and values with type-specific methods).

Specified by:

reference2ReferenceEntrySet in interface Reference2ReferenceMap<K,V>

Returns:

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

See Also:

Reference2ReferenceMap.entrySet()

keySet

public ReferenceSet<K> keySet()

Description copied from class: AbstractReference2ReferenceMap

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

The view is backed by the set returned by AbstractReference2ReferenceMap.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 Reference2ReferenceMap<K,V>

Specified by:

keySet in interface Map<K,V>

Overrides:

keySet in class AbstractReference2ReferenceMap<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 ReferenceCollection<V> values()

Description copied from class: AbstractReference2ReferenceMap

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

The view is backed by the set returned by AbstractReference2ReferenceMap.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 Reference2ReferenceMap<K,V>

Specified by:

values in interface Map<K,V>

Overrides:

values in class AbstractReference2ReferenceMap<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()

rehash

public boolean rehash()

Rehashes this map without changing the table size.

This method should be called when the map underwent numerous deletions and insertions. In this case, free entries become rare, and unsuccessful searches require probing all entries. For reasonable load factors this method is linear in the number of entries. You will need as much additional free memory as that occupied by the table.

If you need to reduce the table siza to fit exactly this map, you must use trim().

Returns:

true if there was enough memory to rehash the map, false otherwise.

See Also:

trim()

trim

public boolean trim()

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

This method rehashes to the smallest size satisfying the load factor. It can be used when the map will not be changed anymore, so to optimize access speed (by collecting deleted entries) and size.

If the table size is already the minimum possible, this method does nothing. If you want to guarantee rehashing, use rehash().

Returns:

true if there was enough memory to trim the map.

See Also:

trim(int), rehash()

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(), rehash()

clone

public Object 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.

Overrides:

clone in class Object

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 Map<K,V>

Overrides:

hashCode in class AbstractReference2ReferenceMap<K,V>

Returns:

a hash code for this map.