abstract class AbstractMultiset<E> extends java.util.AbstractCollection<E> implements Multiset<E>
Multiset
interface. A new multiset
implementation can be created easily by extending this class and implementing the Multiset.entrySet()
method, plus optionally overriding add(Object, int)
and remove(Object, int)
to enable modifications to the multiset.
The Multiset.count(java.lang.Object)
and AbstractCollection.size()
implementations all iterate across the set returned by
Multiset.entrySet()
, as do many methods acting on the set returned by elementSet()
. Override those methods for better performance.
Modifier and Type | Class and Description |
---|---|
(package private) class |
AbstractMultiset.ElementSet |
(package private) class |
AbstractMultiset.EntrySet |
Multiset.Entry<E>
Modifier and Type | Field and Description |
---|---|
private java.util.Set<E> |
elementSet |
private java.util.Set<Multiset.Entry<E>> |
entrySet |
Constructor and Description |
---|
AbstractMultiset() |
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(java.util.Collection<? extends E> elementsToAdd) |
abstract void |
clear() |
boolean |
contains(java.lang.Object element)
Determines whether this multiset contains the specified element.
|
(package private) java.util.Set<E> |
createElementSet()
Creates a new instance of this multiset's element set, which will be returned by
elementSet() . |
(package private) java.util.Set<Multiset.Entry<E>> |
createEntrySet() |
(package private) abstract int |
distinctElements() |
(package private) abstract java.util.Iterator<E> |
elementIterator() |
java.util.Set<E> |
elementSet()
Returns the set of distinct elements contained in this multiset.
|
(package private) abstract java.util.Iterator<Multiset.Entry<E>> |
entryIterator() |
java.util.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(java.lang.Object object)
Compares the specified object with this multiset for equality.
|
int |
hashCode()
Returns the hash code for this multiset.
|
boolean |
isEmpty() |
boolean |
remove(java.lang.Object element)
Removes a single occurrence of the specified element from this multiset, if present.
|
int |
remove(java.lang.Object element,
int occurrences)
Removes a number of occurrences of the specified element from this multiset.
|
boolean |
removeAll(java.util.Collection<?> elementsToRemove) |
boolean |
retainAll(java.util.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. |
java.lang.String |
toString() |
containsAll, iterator, size, toArray, toArray
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
containsAll, count, forEach, forEachEntry, iterator, size, spliterator
@CheckForNull private transient java.util.Set<E> elementSet
@CheckForNull private transient java.util.Set<Multiset.Entry<E>> entrySet
public boolean isEmpty()
public boolean contains(@CheckForNull java.lang.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.
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 java.util.Collection<E>
add
in class java.util.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
typespublic int add(E element, int occurrences)
Multiset
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.public final boolean remove(@CheckForNull java.lang.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.
public int remove(@CheckForNull java.lang.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.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 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
.public final boolean addAll(java.util.Collection<? extends E> elementsToAdd)
This implementation is highly efficient when elementsToAdd
is itself a Multiset
.
public final boolean removeAll(java.util.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.
public final boolean retainAll(java.util.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.
public abstract void clear()
public java.util.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>
java.util.Set<E> createElementSet()
elementSet()
.abstract java.util.Iterator<E> elementIterator()
public java.util.Set<Multiset.Entry<E>> entrySet()
Multiset
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.
java.util.Set<Multiset.Entry<E>> createEntrySet()
abstract java.util.Iterator<Multiset.Entry<E>> entryIterator()
abstract int distinctElements()
public final boolean equals(@CheckForNull java.lang.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 java.lang.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()
.