@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<? extends E> elementsToAdd) |
void |
clear() |
boolean |
contains(@Nullable Object element)
Determines whether this multiset contains the specified element.
|
int |
count(@Nullable Object element)
Returns the number of occurrences of an element in this multiset (the count of the
element).
|
static <E> HashMultiset<E> |
create()
Creates a new, empty
HashMultiset using the default initial capacity. |
static <E> HashMultiset<E> |
create(int distinctElements)
Creates a new, empty
HashMultiset with the specified expected number of distinct
elements. |
static <E> HashMultiset<E> |
create(Iterable<? extends E> elements)
Creates a new
HashMultiset containing the specified elements. |
Set<E> |
elementSet()
Returns the set of distinct elements contained in this multiset.
|
Set<Multiset.Entry<E>> |
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(@Nullable Object object)
Compares the specified object with this multiset for equality.
|
void |
forEachEntry(ObjIntConsumer<? super E> action)
Runs the specified action for each distinct element in this multiset, and the number of
occurrences of that element.
|
int |
hashCode()
Returns the hash code for this multiset.
|
boolean |
isEmpty() |
Iterator<E> |
iterator() |
boolean |
remove(@Nullable Object element)
Removes a single occurrence of the specified element from this multiset, if present.
|
int |
remove(@Nullable Object element,
int occurrences)
Removes a number of occurrences of the specified element from this multiset.
|
boolean |
removeAll(Collection<?> elementsToRemove) |
boolean |
retainAll(Collection<?> elementsToRetain) |
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.setCount(Object, int) , provided that the element has the expected current count. |
int |
size()
Returns the total number of all occurrences of all elements in this multiset.
|
String |
toString() |
containsAll, toArray, toArray
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
containsAll, forEach, spliterator
parallelStream, removeIf, 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 elementsIllegalArgumentException
- if distinctElements
is negativepublic 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 containpublic 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.Entry.getCount()
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 forEachEntry(ObjIntConsumer<? super E> action)
Multiset
Multiset
implementations, this may be more
efficient than iterating over the Multiset.entrySet()
either explicitly or with entrySet().forEach(action)
.forEachEntry
in interface Multiset<E>
public void clear()
clear
in interface Collection<E>
public int size()
Multiset
Note: this method does not return the number of distinct elements in the
multiset, which is given by entrySet().size()
.
size
in interface Multiset<E>
size
in interface Collection<E>
size
in class AbstractCollection<E>
public Iterator<E> iterator()
Multiset
Elements that occur multiple times in the multiset will appear multiple times in this iterator, though not necessarily sequentially.
iterator
in interface Multiset<E>
iterator
in interface Iterable<E>
iterator
in interface Collection<E>
iterator
in class AbstractCollection<E>
public int count(@Nullable Object element)
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.frequency(java.lang.Iterable<?>, java.lang.Object)
generalizes this operation; it
correctly delegates to this method when dealing with a multiset, but it can also accept any
other iterable type.
@CanIgnoreReturnValue 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
implementationoccurrences
- 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.@CanIgnoreReturnValue public int remove(@Nullable Object element, 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 ofoccurrences
- the number of occurrences of the element to remove. May be zero, in which
case no change will be made.@CanIgnoreReturnValue 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 implementationcount
- the desired count of the element in this multisetpublic boolean isEmpty()
isEmpty
in interface Collection<E>
isEmpty
in class AbstractCollection<E>
public boolean contains(@Nullable Object element)
Multiset
This method refines Collection.contains(java.lang.Object)
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 fortrue
if this multiset contains at least one occurrence of the element@CanIgnoreReturnValue public final boolean add(E element)
Multiset
This method refines Collection.add(E)
, 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 implementationtrue
always, since this call is required to modify the multiset, unlike other
Collection
types@CanIgnoreReturnValue public final boolean remove(@Nullable Object element)
Multiset
This method refines Collection.remove(java.lang.Object)
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 oftrue
if an occurrence was found and removed@CanIgnoreReturnValue 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 implementationoldCount
- the expected present count of the element in this multisetnewCount
- the desired count of the element in this multisettrue
if the condition for modification was met. This implies that the multiset
was indeed modified, unless oldCount == newCount
.@CanIgnoreReturnValue public final boolean addAll(Collection<? extends E> elementsToAdd)
This implementation is highly efficient when elementsToAdd
is itself a Multiset
.
addAll
in interface Collection<E>
addAll
in class AbstractCollection<E>
@CanIgnoreReturnValue public final 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.removeOccurrences(Multiset,
Multiset)
.
This method refines Collection.removeAll(java.util.Collection<?>)
to further specify that it may not
throw an exception in response to any of elements
being null or of the wrong type.
removeAll
in interface Multiset<E>
removeAll
in interface Collection<E>
removeAll
in class AbstractCollection<E>
@CanIgnoreReturnValue public final 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.retainOccurrences(Multiset,
Multiset)
.
This method refines Collection.retainAll(java.util.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 final boolean equals(@Nullable Object object)
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 final 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.entrySet()
.
public final String toString()
It is recommended, though not mandatory, that this method return the result of invoking
Multiset.toString()
on the Multiset.entrySet()
, yielding a result such as [a x 3, c, d x 2,
e]
.
This implementation returns the result of invoking toString
on Multiset.entrySet()
.
toString
in interface Multiset<E>
toString
in class AbstractCollection<E>
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