public class Object2ObjectOpenHashMap<K,V> extends AbstractObject2ObjectMap<K,V> implements Serializable, Cloneable, Hash
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.
Hash,
HashCommon,
Serialized FormAbstractObject2ObjectMap.BasicEntry<K,V>, AbstractObject2ObjectMap.BasicEntrySet<K,V>Hash.Strategy<K>Object2ObjectMap.Entry<K,V>, Object2ObjectMap.FastEntrySet<K,V>| Modifier and Type | Field and Description |
|---|---|
protected boolean |
containsNullKey
Whether this map contains the key zero.
|
protected Object2ObjectMap.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 |
minN
We never resize below this threshold, which is the construction-time {#n}.
|
protected int |
n
The current table size.
|
protected int |
size
Number of entries in the set (including the key zero, if present).
|
protected V[] |
value
The array of values.
|
protected ObjectCollection<V> |
values
Cached collection of values.
|
defRetValueDEFAULT_GROWTH_FACTOR, DEFAULT_INITIAL_SIZE, DEFAULT_LOAD_FACTOR, FAST_LOAD_FACTOR, FREE, OCCUPIED, PRIMES, REMOVED, VERY_FAST_LOAD_FACTOR| Constructor and Description |
|---|
Object2ObjectOpenHashMap()
Creates a new hash map with initial expected
Hash.DEFAULT_INITIAL_SIZE entries
and Hash.DEFAULT_LOAD_FACTOR as load factor. |
Object2ObjectOpenHashMap(int expected)
Creates a new hash map with
Hash.DEFAULT_LOAD_FACTOR as load factor. |
Object2ObjectOpenHashMap(int expected,
float f)
Creates a new hash map.
|
Object2ObjectOpenHashMap(K[] k,
V[] v)
Creates a new hash map with
Hash.DEFAULT_LOAD_FACTOR as load factor using the elements of two parallel arrays. |
Object2ObjectOpenHashMap(K[] k,
V[] v,
float f)
Creates a new hash map using the elements of two parallel arrays.
|
Object2ObjectOpenHashMap(Map<? extends K,? extends V> m)
Creates a new hash map with
Hash.DEFAULT_LOAD_FACTOR as load factor copying a given one. |
Object2ObjectOpenHashMap(Map<? extends K,? extends V> m,
float f)
Creates a new hash map copying a given one.
|
Object2ObjectOpenHashMap(Object2ObjectMap<K,V> m)
Creates a new hash map with
Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific one. |
Object2ObjectOpenHashMap(Object2ObjectMap<K,V> m,
float f)
Creates a new hash map copying a given type-specific one.
|
| Modifier and Type | Method and Description |
|---|---|
void |
clear()
Removes all of the mappings from this map (optional operation).
|
Object2ObjectOpenHashMap<K,V> |
clone()
Returns a deep copy of this map.
|
boolean |
containsKey(Object k)
Returns true if this function contains a mapping for the specified key.
|
boolean |
containsValue(Object v) |
V |
get(Object k)
Returns the value to which the given key is mapped.
|
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.
|
Object2ObjectMap.FastEntrySet<K,V> |
object2ObjectEntrySet()
Returns a type-specific set view of the mappings contained in this map.
|
V |
put(K k,
V v)
Adds a pair to the map (optional operation).
|
void |
putAll(Map<? extends K,? extends V> m) |
protected void |
rehash(int newN)
Rehashes the map.
|
V |
remove(Object k)
Removes the mapping with the given key (optional operation).
|
protected void |
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 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.
|
equals, toStringdefaultReturnValue, defaultReturnValuefinalize, getClass, notify, notifyAll, wait, wait, waitdefaultReturnValue, defaultReturnValue, entrySetcompute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAllprotected transient K[] key
protected transient V[] value
protected transient int mask
protected transient boolean containsNullKey
protected transient int n
protected transient int maxFill
f.protected final transient int minN
protected int size
protected final float f
protected transient Object2ObjectMap.FastEntrySet<K,V> entries
protected transient ObjectCollection<V> values
public Object2ObjectOpenHashMap(int expected,
float f)
The actual table size will be the least power of two greater than expected/f.
expected - the expected number of elements in the hash map.f - the load factor.public Object2ObjectOpenHashMap(int expected)
Hash.DEFAULT_LOAD_FACTOR as load factor.expected - the expected number of elements in the hash map.public Object2ObjectOpenHashMap()
Hash.DEFAULT_INITIAL_SIZE entries
and Hash.DEFAULT_LOAD_FACTOR as load factor.public Object2ObjectOpenHashMap(Map<? extends K,? extends V> m, float f)
m - a Map to be copied into the new hash map.f - the load factor.public Object2ObjectOpenHashMap(Map<? extends K,? extends V> m)
Hash.DEFAULT_LOAD_FACTOR as load factor copying a given one.m - a Map to be copied into the new hash map.public Object2ObjectOpenHashMap(Object2ObjectMap<K,V> m, float f)
m - a type-specific map to be copied into the new hash map.f - the load factor.public Object2ObjectOpenHashMap(Object2ObjectMap<K,V> m)
Hash.DEFAULT_LOAD_FACTOR as load factor copying a given type-specific one.m - a type-specific map to be copied into the new hash map.public Object2ObjectOpenHashMap(K[] k, V[] v, float f)
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.IllegalArgumentException - if k and v have different lengths.public Object2ObjectOpenHashMap(K[] k, V[] v)
Hash.DEFAULT_LOAD_FACTOR as load factor using the elements of two parallel arrays.k - the array of keys of the new hash map.v - the array of corresponding values in the new hash map.IllegalArgumentException - if k and v have different lengths.public void putAll(Map<? extends K,? extends V> m)
AbstractObject2ObjectMappublic V put(K k, V v)
Object2ObjectMapThis default implementation just delegates to the corresponding function method.
put in interface Object2ObjectFunction<K,V>put in interface Object2ObjectMap<K,V>put in interface Map<K,V>k - the key.v - the value.Function.put(Object,Object)protected final void shiftKeys(int pos)
pos - a starting position.public V remove(Object k)
Object2ObjectMapThis default implementation just delegates to the corresponding type-specific–function method.
remove in interface Object2ObjectFunction<K,V>remove in interface Object2ObjectMap<K,V>remove in interface Map<K,V>k - the key.Function.remove(Object)public V get(Object k)
Object2ObjectFunctionget in interface Object2ObjectFunction<K,V>get in interface Map<K,V>k - the key.Function.get(Object)public boolean containsKey(Object k)
Object2ObjectMapcontainsKey in interface Object2ObjectMap<K,V>containsKey in interface Map<K,V>containsKey in class AbstractObject2ObjectMap<K,V>k - the key.key.Map.containsKey(Object)public boolean containsValue(Object v)
containsValue in interface Map<K,V>containsValue in class AbstractObject2ObjectMap<K,V>public void clear()
Object2ObjectMapclear in interface Object2ObjectMap<K,V>clear in interface Map<K,V>Map.clear()public int size()
Object2ObjectMapInteger.MAX_VALUE elements, returns Integer.MAX_VALUE.public boolean isEmpty()
public Object2ObjectMap.FastEntrySet<K,V> object2ObjectEntrySet()
Object2ObjectMapThis 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).
object2ObjectEntrySet in interface Object2ObjectMap<K,V>Map.entrySet()public ObjectSet<K> keySet()
AbstractObject2ObjectMapThe 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.
keySet in interface Object2ObjectMap<K,V>keySet in interface Map<K,V>keySet in class AbstractObject2ObjectMap<K,V>Map.keySet()public ObjectCollection<V> values()
AbstractObject2ObjectMapThe 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.
values in interface Object2ObjectMap<K,V>values in interface Map<K,V>values in class AbstractObject2ObjectMap<K,V>Map.values()public boolean trim()
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.
trim(int)public boolean trim(int n)
Let N be the smallest table size that can hold
max(n, 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.
size())
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.
n - the threshold for the trimming.trim()protected void rehash(int newN)
This method implements the basic rehashing strategy, and may be overridden 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.
newN - the new sizepublic Object2ObjectOpenHashMap<K,V> clone()
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.
public int hashCode()
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.Copyright © 2020. All rights reserved.