java.util.AbstractCollection<E>
com.google.common.collect.HashMultiset<E>
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java.lang.Object
public final class HashMultiset<E>
Multiset implementation backed by a HashMap.
| Nested Class Summary |
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| Nested classes/interfaces inherited from interface com.google.common.collect.Multiset |
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Multiset.Entry<E> |
| Method Summary | ||
|---|---|---|
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(Object element)
Returns true if this collection contains the specified element. |
|
boolean |
containsAll(Collection<?> elements)
Returns true if this collection contains all of the elements in the specified collection. |
|
int |
count(Object element)
Returns the number of occurrences of an element in this multiset (the count of the element). |
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static
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create()
Creates a new, empty HashMultiset using the default initial
capacity. |
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static
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create(int distinctElements)
Creates a new, empty HashMultiset with the specified expected
number of distinct elements. |
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static
|
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(Object object)
Indicates whether some other object is "equal to" this one. |
|
int |
hashCode()
Returns a hash code value for the object. |
|
boolean |
isEmpty()
Returns true if this collection contains no elements. |
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Iterator<E> |
iterator()
Returns an iterator over the elements contained in this collection. |
|
boolean |
remove(Object element)
Removes a single instance of the specified element from this collection, if it is present (optional operation). |
|
int |
remove(Object element,
int occurrences)
Removes a number of occurrences of the specified element from this multiset. |
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boolean |
removeAll(Collection<?> elementsToRemove)
Removes all of this collection's elements that are also contained in the specified collection (optional operation). |
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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. |
|
| Methods inherited from class java.util.AbstractCollection |
|---|
toArray, toArray |
| Methods inherited from class java.lang.Object |
|---|
clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
| Methods inherited from interface java.util.Collection |
|---|
toArray, toArray |
| Method Detail |
|---|
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 negativepublic static <E> HashMultiset<E> create(Iterable<? extends E> elements)
HashMultiset containing the specified elements.
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.
entrySet in interface Multiset<E>public int size()
java.util.Collection
size in interface Collection<E>public Iterator<E> iterator()
java.util.AbstractCollection
iterator in interface Multiset<E>iterator in interface Iterable<E>iterator in interface Collection<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.
count in interface Multiset<E>element - the element to count occurrences of
public int add(@Nullable
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.
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.
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 multiset
public 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
public boolean add(@Nullable
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
public boolean remove(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
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 multiset
true if the condition for modification was met. This
implies that the multiset was indeed modified, unless
oldCount == newCount.public boolean containsAll(Collection<?> elements)
java.util.AbstractCollectionThis implementation iterates over the specified collection, checking each element returned by the iterator in turn to see if it's contained in this collection. If all elements are so contained true is returned, otherwise false.
containsAll in interface Multiset<E>containsAll in interface Collection<E>containsAll in class AbstractCollection<E>elements - collection to be checked for containment in this collection
AbstractCollection.contains(Object)public boolean addAll(Collection<? extends E> elementsToAdd)
java.util.AbstractCollectionThis 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).
addAll in interface Collection<E>addAll in class AbstractCollection<E>elementsToAdd - collection containing elements to be added to this collection
AbstractCollection.add(Object)public 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 collection
AbstractCollection.remove(Object),
AbstractCollection.contains(Object)public 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 collection
AbstractCollection.remove(Object),
AbstractCollection.contains(Object)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>clear in class AbstractCollection<E>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 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 other 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 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
JavaTM 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 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>
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