@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)
Ensures that this collection contains the specified element (optional
operation).
|
int |
add(E element,
int occurrences)
Adds a number of occurrences of an element to this multiset.
|
boolean |
addAll(Collection<? extends E> elementsToAdd)
Adds all of the elements in the specified collection to this collection
(optional operation).
|
void |
clear()
Removes all of the elements from this collection (optional operation).
|
boolean |
contains(@Nullable Object element)
Returns true if this collection 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)
Indicates whether some other object is "equal to" this one.
|
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 a hash code value for the object.
|
boolean |
isEmpty()
Returns true if this collection contains no elements.
|
Iterator<E> |
iterator()
Returns an iterator over the elements contained in this collection.
|
boolean |
remove(@Nullable Object element)
Removes a single instance of the specified element from this
collection, if it is present (optional operation).
|
int |
remove(@Nullable Object element,
int occurrences)
Removes a number of occurrences of the specified element from this multiset.
|
boolean |
removeAll(Collection<?> elementsToRemove)
Removes all of this collection's elements that are also contained in the
specified collection (optional operation).
|
boolean |
retainAll(Collection<?> elementsToRetain)
Retains only the elements in this collection that are contained in the
specified collection (optional operation).
|
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 number of elements in this collection.
|
String |
toString()
Returns a string representation of this collection.
|
containsAll, toArray, toArrayclone, finalize, getClass, notify, notifyAll, wait, wait, waitcontainsAll, forEach, spliteratorparallelStream, removeIf, stream, toArray, toArraypublic 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)
MultisetMultiset 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()
java.util.AbstractCollectionThis implementation iterates over this collection, removing each element using the Iterator.remove operation. Most implementations will probably choose to override this method for efficiency.
Note that this implementation will throw an UnsupportedOperationException if the iterator returned by this collection's iterator method does not implement the remove method and this collection is non-empty.
clear in interface Collection<E>public int size()
java.util.Collectionsize in interface Multiset<E>size in interface Collection<E>size in class AbstractCollection<E>public Iterator<E> iterator()
java.util.AbstractCollectioniterator 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)
MultisetObject.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)
Multisetoccurrences == 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)
MultisetsetCount 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()
java.util.AbstractCollectionThis implementation returns size() == 0.
isEmpty in interface Collection<E>isEmpty in class AbstractCollection<E>public boolean contains(@Nullable Object element)
java.util.AbstractCollectionThis implementation iterates over the elements in the collection, checking each element in turn for equality with the specified element.
contains in interface Multiset<E>contains in interface Collection<E>contains in class AbstractCollection<E>element - element whose presence in this collection is to be tested@CanIgnoreReturnValue public final boolean add(E element)
java.util.AbstractCollectionCollections that support this operation may place limitations on what elements may be added to this collection. In particular, some collections will refuse to add null elements, and others will impose restrictions on the type of elements that may be added. Collection classes should clearly specify in their documentation any restrictions on what elements may be added.
If a collection refuses to add a particular element for any reason other than that it already contains the element, it must throw an exception (rather than returning false). This preserves the invariant that a collection always contains the specified element after this call returns.
This implementation always throws an UnsupportedOperationException.
add in interface Multiset<E>add in interface Collection<E>add in class AbstractCollection<E>element - element whose presence in this collection is to be ensured@CanIgnoreReturnValue public final boolean remove(@Nullable Object element)
java.util.AbstractCollectionThis implementation iterates over the collection looking for the specified element. If it finds the element, it removes the element from the collection using the iterator's remove method.
Note that this implementation throws an UnsupportedOperationException if the iterator returned by this collection's iterator method does not implement the remove method and this collection contains the specified object.
remove in interface Multiset<E>remove in interface Collection<E>remove in class AbstractCollection<E>element - element to be removed from this collection, if present@CanIgnoreReturnValue public boolean setCount(E element, int oldCount, int newCount)
MultisetMultiset.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 iterates over the specified collection, and adds each object returned by the iterator to this collection, in turn.
Note that this implementation will throw an UnsupportedOperationException unless add is overridden (assuming the specified collection is non-empty).
This implementation is highly efficient when elementsToAdd is itself a Multiset.
addAll in interface Collection<E>addAll in class AbstractCollection<E>elementsToAdd - collection containing elements to be added to this collectionAbstractCollection.add(Object)@CanIgnoreReturnValue public final boolean removeAll(Collection<?> elementsToRemove)
java.util.AbstractCollectionThis implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection. If it's so contained, it's removed from this collection with the iterator's remove method.
Note that this implementation will throw an UnsupportedOperationException if the iterator returned by the iterator method does not implement the remove method and this collection contains one or more elements in common with the specified collection.
removeAll in interface Multiset<E>removeAll in interface Collection<E>removeAll in class AbstractCollection<E>elementsToRemove - collection containing elements to be removed from this collectionAbstractCollection.remove(Object),
AbstractCollection.contains(Object)@CanIgnoreReturnValue public final boolean retainAll(Collection<?> elementsToRetain)
java.util.AbstractCollectionThis implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection. If it's not so contained, it's removed from this collection with the iterator's remove method.
Note that this implementation will throw an UnsupportedOperationException if the iterator returned by the iterator method does not implement the remove method and this collection contains one or more elements not present in the specified collection.
retainAll in interface Multiset<E>retainAll in interface Collection<E>retainAll in class AbstractCollection<E>elementsToRetain - collection containing elements to be retained in this collectionAbstractCollection.remove(Object),
AbstractCollection.contains(Object)public Set<E> elementSet()
MultisetIf 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)
The equals method implements an equivalence relation
on non-null object references:
x, x.equals(x) should return
true.
x and y, x.equals(y)
should return true if and only if
y.equals(x) returns true.
x, y, and z, if
x.equals(y) returns true and
y.equals(z) returns true, then
x.equals(z) should return true.
x and y, multiple invocations of
x.equals(y) consistently return true
or consistently return false, provided no
information used in equals comparisons on the
objects is modified.
x,
x.equals(null) should return false.
The equals method for class Object implements
the most discriminating possible equivalence relation on objects;
that is, for any non-null reference values x and
y, this method returns true if and only
if x and y refer to the same object
(x == y has the value true).
Note that it is generally necessary to override the hashCode
method whenever this method is overridden, so as to maintain the
general contract for the hashCode method, which states
that equal objects must have equal hash codes.
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.
equals in interface Multiset<E>equals in interface Collection<E>equals in class Objectobject - the reference object with which to compare.true if this object is the same as the obj
argument; false otherwise.Object.hashCode(),
HashMappublic final int hashCode()
HashMap.
The general contract of hashCode is:
hashCode method
must consistently return the same integer, provided no information
used in equals comparisons on the object is modified.
This integer need not remain consistent from one execution of an
application to another execution of the same application.
equals(Object)
method, then calling the hashCode method on each of
the two objects must produce the same integer result.
Object.equals(java.lang.Object)
method, then calling the hashCode method on each of the
two objects must produce distinct integer results. However, the
programmer should be aware that producing distinct integer results
for unequal objects may improve the performance of hash tables.
As much as is reasonably practical, the hashCode method defined by
class Object does return distinct integers for distinct
objects. (This is typically implemented by converting the internal
address of the object into an integer, but this implementation
technique is not required by the
Java™ programming language.)
This implementation returns the hash code of Multiset.entrySet().
hashCode in interface Multiset<E>hashCode in interface Collection<E>hashCode in class ObjectObject.equals(java.lang.Object),
System.identityHashCode(java.lang.Object)public final String toString()
String.valueOf(Object).
This implementation returns the result of invoking toString on Multiset.entrySet().
toString in interface Multiset<E>toString in class AbstractCollection<E>Copyright © 2010–2019. All rights reserved.