it.unimi.dsi.fastutil.objects
Class Object2ObjectOpenHashMap

java.lang.Object
  it.unimi.dsi.fastutil.objects.AbstractObject2ObjectMap
      it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap

All Implemented Interfaces:

Cloneable, Hash, Map, Object2ObjectMap, Serializable

public class Object2ObjectOpenHashMap

extends AbstractObject2ObjectMap

implements Serializable, Cloneable, Hash, Object2ObjectMap

A type-specific hash map with a fast, small-footprint implementation whose hashing strategy is specified at creation time.

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 inherited from class it.unimi.dsi.fastutil.objects.AbstractObject2ObjectMap

AbstractObject2ObjectMap.BasicEntry

Nested classes inherited from class it.unimi.dsi.fastutil.Hash

Hash.Strategy

Nested classes inherited from class it.unimi.dsi.fastutil.objects.Object2ObjectMap

Object2ObjectMap.Entry

Field Summary

static long

serialVersionUID

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

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

Constructor Summary

Object2ObjectOpenHashMap()
Creates a new hash map with Hash.DEFAULT_INITIAL_SIZE entries and Hash.DEFAULT_LOAD_FACTOR as load factor.

Object2ObjectOpenHashMap(int n)
Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor.

Object2ObjectOpenHashMap(int n, float f)
Creates a new hash map.

Object2ObjectOpenHashMap(Map m)
Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given one.

Object2ObjectOpenHashMap(Map m, float f)
Creates a new hash map copying a given one.

Object2ObjectOpenHashMap(Object2ObjectMap m)
Creates a new hash map with Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific one.

Object2ObjectOpenHashMap(Object2ObjectMap m, float f)
Creates a new hash map copying a given type-specific one.

Method Summary

void	clear()
Object	clone() Returns a deep copy of this map.
boolean	containsKey(Object k) Checks whether the given value is contained in keySet().
boolean	containsValue(Object v) Checks whether the given value is contained in values().
Set	entrySet()
Object	get(Object k)
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()
Set	keySet() Returns a type-specific-set view of the keys of this map.
Object	put(Object k, Object v)
boolean	rehash() Rehashes this map without changing the table size.
Object	remove(Object k)
int	size()
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.
Collection	values() Returns a type-specific-set view of the values of this map.

Methods inherited from class it.unimi.dsi.fastutil.objects.AbstractObject2ObjectMap

defaultReturnValue, defaultReturnValue, equals, getDefRetValue, putAll, setDefRetValue, toString

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface it.unimi.dsi.fastutil.objects.Object2ObjectMap

defaultReturnValue, defaultReturnValue, getDefRetValue, setDefRetValue

Methods inherited from interface java.util.Map

equals, putAll

Field Detail

serialVersionUID

public static final long serialVersionUID

See Also:

Constant Field Values

Constructor Detail

Object2ObjectOpenHashMap

public Object2ObjectOpenHashMap(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

Object2ObjectOpenHashMap

public Object2ObjectOpenHashMap(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.

Object2ObjectOpenHashMap

public Object2ObjectOpenHashMap()

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

Object2ObjectOpenHashMap

public Object2ObjectOpenHashMap(Map 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.

Object2ObjectOpenHashMap

public Object2ObjectOpenHashMap(Map 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.

Object2ObjectOpenHashMap

public Object2ObjectOpenHashMap(Object2ObjectMap 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.

Object2ObjectOpenHashMap

public Object2ObjectOpenHashMap(Object2ObjectMap 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.

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 Object put(Object k,
                  Object v)

Specified by:

put in interface Map

Overrides:

put in class AbstractObject2ObjectMap

containsValue

public boolean containsValue(Object v)

Description copied from class: AbstractObject2ObjectMap

Checks whether the given value is contained in AbstractObject2ObjectMap.values().

Specified by:

containsValue in interface Map

Overrides:

containsValue in class AbstractObject2ObjectMap

clear

public void clear()

Specified by:

clear in interface Map

Overrides:

clear in class AbstractObject2ObjectMap

containsKey

public boolean containsKey(Object k)

Description copied from class: AbstractObject2ObjectMap

Checks whether the given value is contained in AbstractObject2ObjectMap.keySet().

Specified by:

containsKey in interface Map

Overrides:

containsKey in class AbstractObject2ObjectMap

size

public int size()

Specified by:

size in interface Map

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Map

Overrides:

isEmpty in class AbstractObject2ObjectMap

get

public Object get(Object k)

Specified by:

get in interface Map

remove

public Object remove(Object k)

Specified by:

remove in interface Map

Overrides:

remove in class AbstractObject2ObjectMap

entrySet

public Set entrySet()

Specified by:

entrySet in interface Map

keySet

public Set keySet()

Description copied from class: AbstractObject2ObjectMap

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 Map

Overrides:

keySet in class AbstractObject2ObjectMap

Returns:

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

values

public Collection values()

Description copied from class: AbstractObject2ObjectMap

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 Map

Overrides:

values in class AbstractObject2ObjectMap

Returns:

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

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 optimise 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 n entries, still satisfying the load factor. If the current table size is smaller than or equal to N, or if the number of elements of this map is larger than 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.

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

Overrides:

hashCode in class AbstractObject2ObjectMap

Returns:

a hash code for this map.