it.unimi.dsi.fastutil.objects

Class Object2ReferenceOpenHashMap<K,V>

java.lang.Object

it.unimi.dsi.fastutil.objects.AbstractObject2ReferenceFunction<K,V>

it.unimi.dsi.fastutil.objects.AbstractObject2ReferenceMap<K,V>

it.unimi.dsi.fastutil.objects.Object2ReferenceOpenHashMap<K,V>

All Implemented Interfaces:

Function<K,V>, Hash, Object2ReferenceFunction<K,V>, Object2ReferenceMap<K,V>, Serializable, Cloneable, Map<K,V>

public class Object2ReferenceOpenHashMap<K,V>
extends AbstractObject2ReferenceMap<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 by doubling its size 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.

Warning: The implementation of this class has significantly changed in fastutil 6.1.0. Please read the comments about this issue in the section “Faster Hash Tables” of the overview.

See Also:

Hash, HashCommon, Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class it.unimi.dsi.fastutil.objects.AbstractObject2ReferenceMap

AbstractObject2ReferenceMap.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.Object2ReferenceMap

Object2ReferenceMap.Entry<K,V>, Object2ReferenceMap.FastEntrySet<K,V>

Field Summary

Fields

Modifier and Type	Field and Description
protected Object2ReferenceMap.FastEntrySet<K,V>	entries Cached set of entries.
protected float	f The acceptable load factor.
protected K[]	key The array of keys.
protected ObjectSet<K>	keys Cached set of keys.
protected int	mask The mask for wrapping a position counter.
protected int	maxFill Threshold after which we rehash.
protected int	n The current table size.
static long	serialVersionUID
protected int	size Number of entries in the set.
protected boolean[]	used The array telling whether a position is used.
protected V[]	value The array of values.
protected ReferenceCollection<V>	values Cached collection of values.

Fields inherited from class it.unimi.dsi.fastutil.objects.AbstractObject2ReferenceFunction

defRetValue

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 and Description
Object2ReferenceOpenHashMap() Creates a new hash map with initial expected Hash.DEFAULT_INITIAL_SIZE entries and Hash.DEFAULT_LOAD_FACTOR as load factor.
Object2ReferenceOpenHashMap(int expected) Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor.
Object2ReferenceOpenHashMap(int expected, float f) Creates a new hash map.
Object2ReferenceOpenHashMap(K[] k, V[] v) Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor using the elements of two parallel arrays.
Object2ReferenceOpenHashMap(K[] k, V[] v, float f) Creates a new hash map using the elements of two parallel arrays.
Object2ReferenceOpenHashMap(Map<? extends K,? extends V> m) Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given one.
Object2ReferenceOpenHashMap(Map<? extends K,? extends V> m, float f) Creates a new hash map copying a given one.
Object2ReferenceOpenHashMap(Object2ReferenceMap<K,V> m) Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific one.
Object2ReferenceOpenHashMap(Object2ReferenceMap<K,V> m, float f) Creates a new hash map copying a given type-specific one.

Method Summary

Methods

Modifier and Type	Method and Description
void	clear() Removes all associations from this function (optional operation).
Object2ReferenceOpenHashMap<K,V>	clone() Returns a deep copy of this map.
boolean	containsKey(Object k) Checks whether the given value is contained in AbstractObject2ReferenceMap.keySet().
boolean	containsValue(Object v) Checks whether the given value is contained in AbstractObject2ReferenceMap.values().
V	get(Object k) Returns the value associated by this function to the specified key.
int	growthFactor() Deprecated. Since fastutil 6.1.0, hash tables are doubled when they are too full.
void	growthFactor(int growthFactor) Deprecated. Since fastutil 6.1.0, hash tables are doubled when they are too full.
int	hashCode() Returns a hash code for this map.
boolean	isEmpty()
ObjectSet<K>	keySet() Returns a type-specific-set view of the keys of this map.
Object2ReferenceMap.FastEntrySet<K,V>	object2ReferenceEntrySet() Returns a type-specific set view of the mappings contained in this map.
V	put(K k, V v) Associates the specified value with the specified key in this function (optional operation).
boolean	rehash() Deprecated. A no-op.
protected void	rehash(int newN) Resizes the map.
V	remove(Object k) Removes this key and the associated value from this function if it is present (optional operation).
protected int	shiftKeys(int pos) Shifts left entries with the specified hash code, starting at the specified position, and empties the resulting free entry.
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.AbstractObject2ReferenceMap

entrySet, equals, putAll, toString

Methods inherited from class it.unimi.dsi.fastutil.objects.AbstractObject2ReferenceFunction

defaultReturnValue, defaultReturnValue

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

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

defaultReturnValue, defaultReturnValue

Field Detail

serialVersionUID

public static final long serialVersionUID

See Also:

Constant Field Values

key

protected transient K[] key

The array of keys.

value

protected transient V[] value

The array of values.

used

protected transient boolean[] used

The array telling whether a position is used.

f

protected final float f

The acceptable load factor.

n

protected transient int n

The current table size.

maxFill

protected transient int maxFill

Threshold after which we rehash. It must be the table size times f.

mask

protected transient int mask

The mask for wrapping a position counter.

size

protected int size

Number of entries in the set.

entries

protected transient volatile Object2ReferenceMap.FastEntrySet<K,V> entries

Cached set of entries.

keys

protected transient volatile ObjectSet<K> keys

Cached set of keys.

values

protected transient volatile ReferenceCollection<V> values

Cached collection of values.

Constructor Detail

Object2ReferenceOpenHashMap

public Object2ReferenceOpenHashMap(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 set.

f - the load factor.

Object2ReferenceOpenHashMap

public Object2ReferenceOpenHashMap(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.

Object2ReferenceOpenHashMap

public Object2ReferenceOpenHashMap()

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

Object2ReferenceOpenHashMap

public Object2ReferenceOpenHashMap(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.

Object2ReferenceOpenHashMap

public Object2ReferenceOpenHashMap(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.

Object2ReferenceOpenHashMap

public Object2ReferenceOpenHashMap(Object2ReferenceMap<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.

Object2ReferenceOpenHashMap

public Object2ReferenceOpenHashMap(Object2ReferenceMap<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.

Object2ReferenceOpenHashMap

public Object2ReferenceOpenHashMap(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.

Object2ReferenceOpenHashMap

public Object2ReferenceOpenHashMap(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

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 AbstractObject2ReferenceFunction<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)

shiftKeys

protected final int shiftKeys(int pos)

Shifts left entries with the specified hash code, starting at the specified position, and empties the resulting free entry.

Parameters:

pos - a starting position.

Returns:

the position cleared by the shifting process.

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 AbstractObject2ReferenceFunction<K,V>

Returns:

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

See Also:

Map.remove(Object)

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)

containsKey

public boolean containsKey(Object k)

Description copied from class: AbstractObject2ReferenceMap

Checks whether the given value is contained in AbstractObject2ReferenceMap.keySet().

Specified by:

containsKey in interface Function<K,V>

Specified by:

containsKey in interface Map<K,V>

Overrides:

containsKey in class AbstractObject2ReferenceMap<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(Object v)

Description copied from class: AbstractObject2ReferenceMap

Checks whether the given value is contained in AbstractObject2ReferenceMap.values().

Specified by:

containsValue in interface Map<K,V>

Overrides:

containsValue in class AbstractObject2ReferenceMap<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 AbstractObject2ReferenceFunction<K,V>

See Also:

Map.clear()

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 AbstractObject2ReferenceMap<K,V>

growthFactor

@Deprecated
public void growthFactor(int growthFactor)

Deprecated. Since fastutil 6.1.0, hash tables are doubled when they are too full.

A no-op for backward compatibility.

Parameters:

growthFactor - unused.

growthFactor

@Deprecated
public int growthFactor()

Deprecated. Since fastutil 6.1.0, hash tables are doubled when they are too full.

Gets the growth factor (2).

Returns:

the growth factor of this set, which is fixed (2).

See Also:

growthFactor(int)

object2ReferenceEntrySet

public Object2ReferenceMap.FastEntrySet<K,V> object2ReferenceEntrySet()

Description copied from interface: Object2ReferenceMap

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 Object2ReferenceMap.entrySet() so that it returns an ObjectSet of objects of type Map.Entry (the latter makes it possible to access keys and values with type-specific methods).

Specified by:

object2ReferenceEntrySet in interface Object2ReferenceMap<K,V>

Returns:

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

See Also:

Object2ReferenceMap.entrySet()

keySet

public ObjectSet<K> keySet()

Description copied from class: AbstractObject2ReferenceMap

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

The view is backed by the set returned by AbstractObject2ReferenceMap.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 Object2ReferenceMap<K,V>

Specified by:

keySet in interface Map<K,V>

Overrides:

keySet in class AbstractObject2ReferenceMap<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: AbstractObject2ReferenceMap

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

The view is backed by the set returned by AbstractObject2ReferenceMap.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 Object2ReferenceMap<K,V>

Specified by:

values in interface Map<K,V>

Overrides:

values in class AbstractObject2ReferenceMap<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

@Deprecated
public boolean rehash()

Deprecated. A no-op.

A no-op for backward compatibility. The kind of tables implemented by this class never need rehashing.

If you need to reduce the table size to fit exactly this set, use trim().

Returns:

true.

See Also:

trim()

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()

rehash

protected void rehash(int newN)

Resizes the map.

This method implements the basic rehashing strategy, and may be overriden by subclasses implementing different rehashing strategies (e.g., disk-based rehashing). However, you should not override this method unless you understand the internal workings of this class.

Parameters:

newN - the new size

clone

public Object2ReferenceOpenHashMap<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.

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 AbstractObject2ReferenceMap<K,V>

Returns:

a hash code for this map.