@GwtCompatible(serializable=true, emulated=true) public final class HashMultiset<E> extends AbstractCollection<E>
HashMap
.
Multiset.Entry <E>
Modifier and Type | Method and Description |
---|---|
boolean |
add(E element)
Adds a single occurrence of the specified element to this multiset.
|
int |
add(E element, int occurrences)
Adds a number of occurrences of an element to this multiset.
|
boolean |
addAll(Collection
|
void |
clear()
|
boolean |
contains(Object
Determines whether this multiset contains the specified element.
|
int |
count(Object
Returns the number of occurrences of an element in this multiset (the
count of the element).
|
static <E> HashMultiset |
create()
Creates a new, empty
HashMultiset using the default initial capacity.
|
static <E> HashMultiset |
create(int distinctElements)
Creates a new, empty
HashMultiset with the specified expected number of distinct elements.
|
static <E> HashMultiset |
create(Iterable
Creates a new
HashMultiset containing the specified elements.
|
Set |
elementSet()
Returns the set of distinct elements contained in this multiset.
|
Set |
entrySet()
Returns a view of the contents of this multiset, grouped into
Multiset.Entry instances, each providing an element of the multiset and the count of that element.
|
boolean |
equals(Object
Compares the specified object with this multiset for equality.
|
int |
hashCode()
Returns the hash code for this multiset.
|
boolean |
isEmpty()
|
Iterator |
iterator()
|
boolean |
remove(Object
Removes a
single occurrence of the specified element from this multiset, if present.
|
int |
remove(Object
Removes a number of occurrences of the specified element from this multiset.
|
boolean |
removeAll(Collection
|
boolean |
retainAll(Collection
|
int |
setCount(E element, int count)
Adds or removes the necessary occurrences of an element such that the element attains the desired count.
|
boolean |
setCount(E element, int oldCount, int newCount)
Conditionally sets the count of an element to a new value, as described in
Multiset , provided that the element has the expected current count.
|
int |
size()
|
String |
toString()
|
containsAll, toArray, toArray
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
containsAll
parallelStream, removeIf, spliterator, stream, toArray, toArray
public static <E> HashMultiset<E> create()
HashMultiset
using the default initial capacity.
public static <E> HashMultiset<E> create(int distinctElements)
HashMultiset
with the specified expected number of distinct elements.
distinctElements
- the expected number of distinct elements
IllegalArgumentException
- if
distinctElements
is negative
public static <E> HashMultiset<E> create(Iterable <? extends E> elements)
HashMultiset
containing the specified elements.
This implementation is highly efficient when elements
is itself a Multiset
.
elements
- the elements that the multiset should contain
public Set<Multiset .Entry <E>> entrySet()
Multiset.Entry
instances, each providing an element of the multiset and the count of that element. This set contains exactly one entry for each distinct element in the multiset (thus it always has the same size as the
Multiset.elementSet()
). The order of the elements in the element set is unspecified.
The entry set is backed by the same data as the multiset, so any change to either is immediately reflected in the other. However, multiset changes may or may not be reflected in any Entry
instances already retrieved from the entry set (this is implementation-dependent). Furthermore, implementations are not required to support modifications to the entry set at all, and the Entry
instances themselves don't even have methods for modification. See the specific implementation class for more details on how its entry set handles modifications.
Invoking Multiset
on an entry in the returned set always returns the current count of that element in the multiset, as opposed to the count at the time the entry was retrieved.
public void clear()
public int size()
public Iterator<E> iterator()
Multiset
Elements that occur multiple times in the multiset will appear multiple times in this iterator, though not necessarily sequentially.
public int count(Objectelement)
Multiset
Object.equals(java.lang.Object)
-based multiset, this gives the same result as
Collections.frequency(java.util.Collection<?>, java.lang.Object)
(which would presumably perform more poorly).
Note: the utility method Iterables
generalizes this operation; it correctly delegates to this method when dealing with a multiset, but it can also accept any other iterable type.
public int add(E element, int occurrences)
occurrences == 1
, this method has the identical effect to
Multiset.add(Object)
. This method is functionally equivalent (except in the case of overflow) to the call
addAll(Collections.nCopies(element, occurrences))
, which would presumably perform much more poorly.
add
in interface
Multiset<E>
element
- the element to add occurrences of; may be null only if explicitly allowed by the implementation
occurrences
- the number of occurrences of the element to add. May be zero, in which case no change will be made.
IllegalArgumentException
- if the call would result in more than
Integer.MAX_VALUE
occurrences of
element
in this multiset.
public int remove(Objectelement, int occurrences)
Multiset
occurrences == 1
, this is functionally equivalent to the call
remove(element)
.
remove
in interface
Multiset<E>
element
- the element to conditionally remove occurrences of
occurrences
- the number of occurrences of the element to remove. May be zero, in which case no change will be made.
public int setCount(E element, int count)
Multiset
setCount
in interface
Multiset<E>
element
- the element to add or remove occurrences of; may be null only if explicitly allowed by the implementation
count
- the desired count of the element in this multiset
public boolean isEmpty()
public boolean contains(Objectelement)
Multiset
This method refines Collection
to further specify that it may not throw an exception in response to element
being null or of the wrong type.
contains
in interface
Multiset<E>
contains
in interface
Collection<E>
contains
in class
AbstractCollection<E>
element
- the element to check for
true
if this multiset contains at least one occurrence of the element
public boolean add(E element)
Multiset
This method refines Collection
, which only ensures the presence of the element, to further specify that a successful call must always increment the count of the element, and the overall size of the collection, by one.
To both add the element and obtain the previous count of that element, use add
(element, 1)
instead.
add
in interface
Multiset<E>
add
in interface
Collection<E>
add
in class
AbstractCollection<E>
element
- the element to add one occurrence of; may be null only if explicitly allowed by the implementation
true
always, since this call is required to modify the multiset, unlike other
Collection
types
public boolean remove(Objectelement)
Multiset
This method refines Collection
to further specify that it may not throw an exception in response to element
being null or of the wrong type.
To both remove the element and obtain the previous count of that element, use remove
(element, 1)
instead.
remove
in interface
Multiset<E>
remove
in interface
Collection<E>
remove
in class
AbstractCollection<E>
element
- the element to remove one occurrence of
true
if an occurrence was found and removed
public boolean setCount(E element, int oldCount, int newCount)
Multiset
Multiset.setCount(Object, int)
, provided that the element has the expected current count. If the current count is not
oldCount
, no change is made.
setCount
in interface
Multiset<E>
element
- the element to conditionally set the count of; may be null only if explicitly allowed by the implementation
oldCount
- the expected present count of the element in this multiset
newCount
- the desired count of the element in this multiset
true
if the condition for modification was met. This implies that the multiset was indeed modified, unless
oldCount == newCount
.
public boolean addAll(Collection<? extends E> elementsToAdd)
This implementation is highly efficient when elementsToAdd
is itself a Multiset
.
public boolean removeAll(Collection<?> elementsToRemove)
Multiset
Note: This method ignores how often any element might appear in c
, and only cares whether or not an element appears at all. If you wish to remove one occurrence in this multiset for every occurrence in c
, see Multisets
.
This method refines Collection
to further specify that it may not throw an exception in response to any of elements
being null or of the wrong type.
public boolean retainAll(Collection<?> elementsToRetain)
Multiset
Note: This method ignores how often any element might appear in c
, and only cares whether or not an element appears at all. If you wish to remove one occurrence in this multiset for every occurrence in c
, see Multisets
.
This method refines Collection
to further specify that it may not throw an exception in response to any of elements
being null or of the wrong type.
retainAll
in interface
Multiset<E>
retainAll
in interface
Collection<E>
retainAll
in class
AbstractCollection<E>
Multisets.retainOccurrences(Multiset, Multiset)
public Set<E> elementSet()
Multiset
If the element set supports any removal operations, these necessarily cause all occurrences of the removed element(s) to be removed from the multiset. Implementations are not expected to support the add operations, although this is possible.
A common use for the element set is to find the number of distinct elements in the multiset: elementSet().size()
.
elementSet
in interface
Multiset<E>
public boolean equals(Objectobject)
true
if the given object is also a multiset and contains equal elements with equal counts, regardless of order.
This implementation returns true
if object
is a multiset of the same size and if, for each element, the two multisets have the same count.
public int hashCode()
((element == null) ? 0 : element.hashCode()) ^ count(element)
over all distinct elements in the multiset. It follows that a multiset and its entry set always have the same hash code.
This implementation returns the hash code of Multiset
.
public StringtoString()
It is recommended, though not mandatory, that this method return the result of invoking Multiset
on the Multiset
, yielding a result such as [a x 3, c, d x 2, e]
.
This implementation returns the result of invoking toString
on Multiset
.