Guava: Google Core Libraries for Java 32.1.2-jre · com.google.common.collect.Multiset

A collection that supports order-independent equality, like Set, but may have duplicate elements. A multiset is also sometimes called a bag.

Elements of a multiset that are equal to one another are referred to as occurrences of the same single element. The total number of occurrences of an element in a multiset is called the count of that element (the terms "frequency" and "multiplicity" are equivalent, but not used in this API). Since the count of an element is represented as an int, a multiset may never contain more than Integer#MAX_VALUE occurrences of any one element.

Multiset refines the specifications of several methods from Collection. It also defines an additional query operation, count, which returns the count of an element. There are five new bulk-modification operations, for example add(Object, int), to add or remove multiple occurrences of an element at once, or to set the count of an element to a specific value. These modification operations are optional, but implementations which support the standard collection operations add(Object) or remove(Object) are encouraged to implement the related methods as well. Finally, two collection views are provided: elementSet contains the distinct elements of the multiset "with duplicates collapsed", and entrySet is similar but contains Multiset.Entry instances, each providing both a distinct element and the count of that element.

In addition to these required methods, implementations of Multiset are expected to provide two static creation methods: create(), returning an empty multiset, and create(Iterable<? extends E>), returning a multiset containing the given initial elements. This is simply a refinement of Collection's constructor recommendations, reflecting the new developments of Java 5.

As with other collection types, the modification operations are optional, and should throw UnsupportedOperationException when they are not implemented. Most implementations should support either all add operations or none of them, all removal operations or none of them, and if and only if all of these are supported, the setCount methods as well.

A multiset uses Object#equals to determine whether two instances should be considered "the same," unless specified otherwise by the implementation.

Warning

as with normal Sets, it is almost always a bad idea to modify an element (in a way that affects its Object#equals behavior) while it is contained in a multiset. Undefined behavior and bugs will result.

Implementations

If your values may be zero, negative, or outside the range of an int, you may wish to use com.google.common.util.concurrent.AtomicLongMap instead. Note, however, that unlike Multiset, AtomicLongMap does not automatically remove zeros.

See the Guava User Guide article on Multiset.

Nested and Inner Type Summary

Modifier and Type	Class and Description
public static interface	Multiset.Entry<E extends @Nullable Object> An unmodifiable element-count pair for a multiset.

Method Summary

Modifier and Type	Method and Description
public int	Returns: the count of the element before the operation; possibly zero add(E the element to add occurrences of; may be null only if explicitly allowed by the implementation element, int the number of occurrences of the element to add. May be zero, in which case no change will be made. occurrences) Adds a number of occurrences of an element to this multiset.
public boolean	Returns: `true` always, since this call is required to modify the multiset, unlike other `Collection` types add(E the element to add one occurrence of; may be null only if explicitly allowed by the implementation element) Redeclares java.util.Collection.add. Adds a single occurrence of the specified element to this multiset.
public boolean	Returns: `true` if this multiset contains at least one occurrence of the element contains(Object the element to check for element) Redeclares java.util.Collection.contains. Determines whether this multiset contains the specified element.
public boolean	Returns: `true` if this multiset contains at least one occurrence of each element contained in `elements` containsAll(Collection<?> the collection of elements to be checked for containment in this multiset elements) Redeclares java.util.Collection.containsAll. Returns `true` if this multiset contains at least one occurrence of each element in the specified collection.
public int	Returns: the number of occurrences of the element in this multiset; possibly zero but never negative count(Object the element to count occurrences of element) Returns the number of occurrences of an element in this multiset (the count of the element).
public Set<E>	Returns: a view of the set of distinct elements in this multiset elementSet() Returns the set of distinct elements contained in this multiset.
public Set<Multiset.Entry<E>>	Returns: a set of entries representing the data of this multiset 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.
public boolean	equals(Object object to be compared for equality with this collection object) Redeclares java.util.Collection.equals. Compares the specified object with this multiset for equality.
public default void	forEach(Consumer<? super E> The action to be performed for each element action) Overrides default java.lang.Iterable.forEach. Performs the given action for each element of the `Iterable` until all elements have been processed or the action throws an exception.
public default 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.
public int	hashCode() Redeclares java.util.Collection.hashCode. Returns the hash code for this multiset.
public Iterator<E>	iterator() Redeclares java.util.Collection.iterator. Returns an iterator over the elements in this collection.
public int	Returns: the count of the element before the operation; possibly zero remove(Object the element to conditionally remove occurrences of element, int the number of occurrences of the element to remove. May be zero, in which case no change will be made. occurrences) Removes a number of occurrences of the specified element from this multiset.
public boolean	Returns: `true` if an occurrence was found and removed remove(Object the element to remove one occurrence of element) Redeclares java.util.Collection.remove. Removes a single occurrence of the specified element from this multiset, if present.
public boolean	removeAll(Collection<?> collection containing elements to be removed from this collection c) Redeclares java.util.Collection.removeAll. Removes all of this collection's elements that are also contained in the specified collection (optional operation).
public boolean	retainAll(Collection<?> collection containing elements to be retained in this collection c) Redeclares java.util.Collection.retainAll. Retains only the elements in this collection that are contained in the specified collection (optional operation).
public int	Returns: the count of the element before the operation; possibly zero setCount(E the element to add or remove occurrences of; may be null only if explicitly allowed by the implementation element, int the desired count of the element in this multiset count) Adds or removes the necessary occurrences of an element such that the element attains the desired count.
public boolean	Returns: `true` if the condition for modification was met. This implies that the multiset was indeed modified, unless `oldCount == newCount`. setCount(E the element to conditionally set the count of; may be null only if explicitly allowed by the implementation element, int the expected present count of the element in this multiset oldCount, int the desired count of the element in this multiset newCount) Conditionally sets the count of an element to a new value, as described in `setCount(Object, int)`, provided that the element has the expected current count.
public int	size() Redeclares java.util.Collection.size. Returns the total number of all occurrences of all elements in this multiset.
public default Spliterator<E>	spliterator() Overrides default java.util.Collection.spliterator. Creates a `Spliterator` over the elements in this collection.
public String	toString() It is recommended, though not mandatory, that this method return the result of invoking `toString` on the `entrySet`, yielding a result such as `[a x 3, c, d x 2, e]`.

Inherited from java.util.Collection:: addAll clear isEmpty parallelStream removeIf stream toArray toArray toArray

Method Detail

add back to summary

add	back to summary
public int add(E element, int occurrences) Adds a number of occurrences of an element to this multiset. Note that if `occurrences == 1`, this method has the identical effect to `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. Parameters element:E the element to add occurrences of; may be null only if explicitly allowed by the implementation occurrences:int the number of occurrences of the element to add. May be zero, in which case no change will be made. Returns:int the count of the element before the operation; possibly zero Annotations @CanIgnoreReturnValue Exceptions IllegalArgumentException: if `occurrences` is negative, or if this operation would result in more than `Integer#MAX_VALUE` occurrences of the element NullPointerException: if `element` is null and this implementation does not permit null elements. Note that if `occurrences` is zero, the implementation may opt to return normally.

public int add(E element, int occurrences)

Adds a number of occurrences of an element to this multiset. Note that if occurrences == 1, this method has the identical effect to 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.

Parameters

element:E: the element to add occurrences of; may be null only if explicitly allowed by the implementation
occurrences:int: the number of occurrences of the element to add. May be zero, in which case no change will be made.

Returns:int

the count of the element before the operation; possibly zero

Annotations

@CanIgnoreReturnValue

Exceptions

IllegalArgumentException:: if occurrences is negative, or if this operation would result in more than Integer#MAX_VALUE occurrences of the element
NullPointerException:: if element is null and this implementation does not permit null elements. Note that if occurrences is zero, the implementation may opt to return normally.

add back to summary

add	back to summary
public boolean add(E element) Redeclares java.util.Collection.add. Adds a single occurrence of the specified element to this multiset. This method refines `Collection#add`, 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. Parameters element:E the element to add one occurrence of; may be null only if explicitly allowed by the implementation Returns:boolean `true` always, since this call is required to modify the multiset, unlike other `Collection` types Annotations @CanIgnoreReturnValue @Override Exceptions NullPointerException: if `element` is null and this implementation does not permit null elements IllegalArgumentException: if `Integer#MAX_VALUE` occurrences of `element` are already contained in this multiset

public boolean add(E element)

Redeclares java.util.Collection.add.

Adds a single occurrence of the specified element to this multiset.

This method refines Collection#add, 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.

Parameters

element:E: the element to add one occurrence of; may be null only if explicitly allowed by the implementation

Returns:boolean

true always, since this call is required to modify the multiset, unlike other Collection types

Annotations

@CanIgnoreReturnValue
@Override

Exceptions

NullPointerException:: if element is null and this implementation does not permit null elements
IllegalArgumentException:: if Integer#MAX_VALUE occurrences of element are already contained in this multiset

contains back to summary

contains	back to summary
public boolean contains(Object element) Redeclares java.util.Collection.contains. Determines whether this multiset contains the specified element. This method refines `Collection#contains` to further specify that it may not throw an exception in response to `element` being null or of the wrong type. Parameters element:Object the element to check for Returns:boolean `true` if this multiset contains at least one occurrence of the element Annotations @Override

public boolean contains(Object element)

Redeclares java.util.Collection.contains.

Determines whether this multiset contains the specified element.

This method refines Collection#contains to further specify that it may not throw an exception in response to element being null or of the wrong type.

Parameters

element:Object: the element to check for

Returns:boolean

true if this multiset contains at least one occurrence of the element

Annotations

@Override

containsAll back to summary

containsAll	back to summary
public boolean containsAll(Collection<?> elements) Redeclares java.util.Collection.containsAll. Returns `true` if this multiset contains at least one occurrence of each element in the specified collection. This method refines `Collection#containsAll` to further specify that it may not throw an exception in response to any of `elements` being null or of the wrong type. Note this method does not take into account the occurrence count of an element in the two collections; it may still return `true` even if `elements` contains several occurrences of an element and this multiset contains only one. This is no different than any other collection type like `List`, but it may be unexpected to the user of a multiset. Parameters elements:Collection<?> the collection of elements to be checked for containment in this multiset Returns:boolean `true` if this multiset contains at least one occurrence of each element contained in `elements` Annotations @Override Exceptions NullPointerException: if `elements` is null

public boolean containsAll(Collection<?> elements)

Redeclares java.util.Collection.containsAll.

Returns true if this multiset contains at least one occurrence of each element in the specified collection.

This method refines Collection#containsAll to further specify that it may not throw an exception in response to any of elements being null or of the wrong type.

Note

this method does not take into account the occurrence count of an element in the two collections; it may still return true even if elements contains several occurrences of an element and this multiset contains only one. This is no different than any other collection type like List, but it may be unexpected to the user of a multiset.

Parameters

elements:Collection<?>: the collection of elements to be checked for containment in this multiset

Returns:boolean

true if this multiset contains at least one occurrence of each element contained in elements

Annotations

@Override

Exceptions

NullPointerException:: if elements is null

count back to summary

count	back to summary
public int count(Object element) Returns the number of occurrences of an element in this multiset (the count of the element). Note that for an `Object#equals`-based multiset, this gives the same result as `Collections#frequency` (which would presumably perform more poorly). Note the utility method `Iterables#frequency` generalizes this operation; it correctly delegates to this method when dealing with a multiset, but it can also accept any other iterable type. Parameters element:Object the element to count occurrences of Returns:int the number of occurrences of the element in this multiset; possibly zero but never negative

public int count(Object element)

Returns the number of occurrences of an element in this multiset (the count of the element). Note that for an Object#equals-based multiset, this gives the same result as Collections#frequency (which would presumably perform more poorly).

Note

the utility method Iterables#frequency generalizes this operation; it correctly delegates to this method when dealing with a multiset, but it can also accept any other iterable type.

Parameters

element:Object: the element to count occurrences of

Returns:int

the number of occurrences of the element in this multiset; possibly zero but never negative

elementSet back to summary

elementSet	back to summary
public Set<E> elementSet() Returns the set of distinct elements contained in this multiset. The element set is backed by the same data as the multiset, so any change to either is immediately reflected in the other. The order of the elements in the element set is unspecified. 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()`. Returns:Set<E> a view of the set of distinct elements in this multiset

public Set<E> elementSet()

Returns the set of distinct elements contained in this multiset. The element set is backed by the same data as the multiset, so any change to either is immediately reflected in the other. The order of the elements in the element set is unspecified.

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().

Returns:Set<E>: a view of the set of distinct elements in this multiset

entrySet back to summary

entrySet	back to summary
public 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. This set contains exactly one entry for each distinct element in the multiset (thus it always has the same size as the `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. Returns:Set<Multiset.Entry<E>> a set of entries representing the data of this multiset

public 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. This set contains exactly one entry for each distinct element in the multiset (thus it always has the same size as the 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.

Returns:Set<Multiset.Entry<E>>: a set of entries representing the data of this multiset

equals back to summary

equals	back to summary
public boolean equals(Object object) Redeclares java.util.Collection.equals. Compares the specified object with this multiset for equality. Returns `true` if the given object is also a multiset and contains equal elements with equal counts, regardless of order. Parameters object:Object Doc from java.util.Collection.equals. object to be compared for equality with this collection Returns:boolean Doc from java.util.Collection.equals. `true` if the specified object is equal to this collection Annotations @Override

public boolean equals(Object object)

Redeclares java.util.Collection.equals.

Compares the specified object with this multiset for equality. Returns true if the given object is also a multiset and contains equal elements with equal counts, regardless of order.

Parameters

object:Object

Doc from java.util.Collection.equals.

object to be compared for equality with this collection

Returns:boolean

Doc from java.util.Collection.equals.

true if the specified object is equal to this collection

Annotations

@Override

forEach back to summary

forEach	back to summary
public default void forEach(Consumer<? super E> action) Overrides default java.lang.Iterable.forEach. Doc from java.lang.Iterable.forEach. Performs the given action for each element of the `Iterable` until all elements have been processed or the action throws an exception. Actions are performed in the order of iteration, if that order is specified. Exceptions thrown by the action are relayed to the caller. The behavior of this method is unspecified if the action performs side-effects that modify the underlying source of elements, unless an overriding class has specified a concurrent modification policy. Elements that occur multiple times in the multiset will be passed to the `Consumer` correspondingly many times, though not necessarily sequentially. Parameters action:Consumer<? super E> The action to be performed for each element Annotations @Override

public default void forEach(Consumer<? super E> action)

Overrides default java.lang.Iterable.forEach.

Doc from java.lang.Iterable.forEach.

Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception. Actions are performed in the order of iteration, if that order is specified. Exceptions thrown by the action are relayed to the caller.

The behavior of this method is unspecified if the action performs side-effects that modify the underlying source of elements, unless an overriding class has specified a concurrent modification policy.

Elements that occur multiple times in the multiset will be passed to the Consumer correspondingly many times, though not necessarily sequentially.

Parameters

action:Consumer<? super E>: The action to be performed for each element

Annotations

@Override

forEachEntry back to summary

forEachEntry	back to summary
public default 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. For some `Multiset` implementations, this may be more efficient than iterating over the `entrySet()` either explicitly or with `entrySet().forEach(action)`. Since 21.0

public default 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. For some Multiset implementations, this may be more efficient than iterating over the entrySet() either explicitly or with entrySet().forEach(action).

Since: 21.0

hashCode back to summary

hashCode	back to summary
public int hashCode() Redeclares java.util.Collection.hashCode. Returns the hash code for this multiset. This is defined as the sum of `((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. Returns:int Doc from java.util.Collection.hashCode. the hash code value for this collection Annotations @Override

public int hashCode()

Redeclares java.util.Collection.hashCode.

Returns the hash code for this multiset. This is defined as the sum of

((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.

Returns:int

Doc from java.util.Collection.hashCode.

the hash code value for this collection

Annotations

@Override

iterator back to summary

iterator	back to summary
public Iterator<E> iterator() Redeclares java.util.Collection.iterator. Doc from java.util.Collection.iterator. Returns an iterator over the elements in this collection. There are no guarantees concerning the order in which the elements are returned (unless this collection is an instance of some class that provides a guarantee). Elements that occur multiple times in the multiset will appear multiple times in this iterator, though not necessarily sequentially. Returns:Iterator<E> an `Iterator` over the elements in this collection Annotations @Override

public Iterator<E> iterator()

Redeclares java.util.Collection.iterator.

Doc from java.util.Collection.iterator.

Returns an iterator over the elements in this collection. There are no guarantees concerning the order in which the elements are returned (unless this collection is an instance of some class that provides a guarantee).

Elements that occur multiple times in the multiset will appear multiple times in this iterator, though not necessarily sequentially.

Returns:Iterator<E>

an Iterator over the elements in this collection

Annotations

@Override

remove back to summary

remove	back to summary
public int remove(Object element, int occurrences) Removes a number of occurrences of the specified element from this multiset. If the multiset contains fewer than this number of occurrences to begin with, all occurrences will be removed. Note that if `occurrences == 1`, this is functionally equivalent to the call `remove(element)`. Parameters element:Object the element to conditionally remove occurrences of occurrences:int the number of occurrences of the element to remove. May be zero, in which case no change will be made. Returns:int the count of the element before the operation; possibly zero Annotations @CanIgnoreReturnValue Exceptions IllegalArgumentException: if `occurrences` is negative

public int remove(Object element, int occurrences)

Removes a number of occurrences of the specified element from this multiset. If the multiset contains fewer than this number of occurrences to begin with, all occurrences will be removed. Note that if occurrences == 1, this is functionally equivalent to the call remove(element).

Parameters

element:Object: the element to conditionally remove occurrences of
occurrences:int: the number of occurrences of the element to remove. May be zero, in which case no change will be made.

Returns:int

the count of the element before the operation; possibly zero

Annotations

@CanIgnoreReturnValue

Exceptions

IllegalArgumentException:: if occurrences is negative

remove back to summary

remove	back to summary
public boolean remove(Object element) Redeclares java.util.Collection.remove. Removes a single occurrence of the specified element from this multiset, if present. This method refines `Collection#remove` 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. Parameters element:Object the element to remove one occurrence of Returns:boolean `true` if an occurrence was found and removed Annotations @CanIgnoreReturnValue @Override

public boolean remove(Object element)

Redeclares java.util.Collection.remove.

Removes a single occurrence of the specified element from this multiset, if present.

This method refines Collection#remove 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.

Parameters

element:Object: the element to remove one occurrence of

Returns:boolean

true if an occurrence was found and removed

Annotations

@CanIgnoreReturnValue
@Override

removeAll back to summary

removeAll	back to summary
public boolean removeAll(Collection<?> c) Redeclares java.util.Collection.removeAll. Doc from java.util.Collection.removeAll. Removes all of this collection's elements that are also contained in the specified collection (optional operation). After this call returns, this collection will contain no elements in common with the specified collection. 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` to further specify that it may not throw an exception in response to any of `elements` being null or of the wrong type. Parameters c:Collection<?> collection containing elements to be removed from this collection Returns:boolean `true` if this collection changed as a result of the call Annotations @CanIgnoreReturnValue @Override

public boolean removeAll(Collection<?> c)

Redeclares java.util.Collection.removeAll.

Doc from java.util.Collection.removeAll.

Removes all of this collection's elements that are also contained in the specified collection (optional operation). After this call returns, this collection will contain no elements in common with the specified collection.

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 to further specify that it may not throw an exception in response to any of elements being null or of the wrong type.

Parameters

c:Collection<?>: collection containing elements to be removed from this collection

Returns:boolean

true if this collection changed as a result of the call

Annotations

@CanIgnoreReturnValue
@Override

retainAll back to summary

retainAll	back to summary
public boolean retainAll(Collection<?> c) Redeclares java.util.Collection.retainAll. Doc from java.util.Collection.retainAll. Retains only the elements in this collection that are contained in the specified collection (optional operation). In other words, removes from this collection all of its elements that are not contained in the specified collection. 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` to further specify that it may not throw an exception in response to any of `elements` being null or of the wrong type. Parameters c:Collection<?> collection containing elements to be retained in this collection Returns:boolean `true` if this collection changed as a result of the call Annotations @CanIgnoreReturnValue @Override See Also `Multisets#retainOccurrences(Multiset, Multiset)`

public boolean retainAll(Collection<?> c)

Redeclares java.util.Collection.retainAll.

Doc from java.util.Collection.retainAll.

Retains only the elements in this collection that are contained in the specified collection (optional operation). In other words, removes from this collection all of its elements that are not contained in the specified collection.

Note

This method refines Collection#retainAll to further specify that it may not throw an exception in response to any of elements being null or of the wrong type.

Parameters

c:Collection<?>: collection containing elements to be retained in this collection

Returns:boolean

true if this collection changed as a result of the call

Annotations

@CanIgnoreReturnValue
@Override

setCount back to summary

setCount	back to summary
public int setCount(E element, int count) Adds or removes the necessary occurrences of an element such that the element attains the desired count. Parameters element:E the element to add or remove occurrences of; may be null only if explicitly allowed by the implementation count:int the desired count of the element in this multiset Returns:int the count of the element before the operation; possibly zero Annotations @CanIgnoreReturnValue Exceptions IllegalArgumentException: if `count` is negative NullPointerException: if `element` is null and this implementation does not permit null elements. Note that if `count` is zero, the implementor may optionally return zero instead.

public int setCount(E element, int count)

Adds or removes the necessary occurrences of an element such that the element attains the desired count.

Parameters

element:E: the element to add or remove occurrences of; may be null only if explicitly allowed by the implementation
count:int: the desired count of the element in this multiset

Returns:int

the count of the element before the operation; possibly zero

Annotations

@CanIgnoreReturnValue

Exceptions

IllegalArgumentException:: if count is negative
NullPointerException:: if element is null and this implementation does not permit null elements. Note that if count is zero, the implementor may optionally return zero instead.

setCount back to summary

setCount	back to summary
public boolean setCount(E element, int oldCount, int newCount) Conditionally sets the count of an element to a new value, as described in `setCount(Object, int)`, provided that the element has the expected current count. If the current count is not `oldCount`, no change is made. Parameters element:E the element to conditionally set the count of; may be null only if explicitly allowed by the implementation oldCount:int the expected present count of the element in this multiset newCount:int the desired count of the element in this multiset Returns:boolean `true` if the condition for modification was met. This implies that the multiset was indeed modified, unless `oldCount == newCount`. Annotations @CanIgnoreReturnValue Exceptions IllegalArgumentException: if `oldCount` or `newCount` is negative NullPointerException: if `element` is null and the implementation does not permit null elements. Note that if `oldCount` and `newCount` are both zero, the implementor may optionally return `true` instead.

public boolean setCount(E element, int oldCount, int newCount)

Conditionally sets the count of an element to a new value, as described in setCount(Object, int), provided that the element has the expected current count. If the current count is not oldCount, no change is made.

Parameters

element:E: the element to conditionally set the count of; may be null only if explicitly allowed by the implementation
oldCount:int: the expected present count of the element in this multiset
newCount:int: the desired count of the element in this multiset

Returns:boolean

true if the condition for modification was met. This implies that the multiset was indeed modified, unless oldCount == newCount.

Annotations

@CanIgnoreReturnValue

Exceptions

IllegalArgumentException:: if oldCount or newCount is negative
NullPointerException:: if element is null and the implementation does not permit null elements. Note that if oldCount and newCount are both zero, the implementor may optionally return true instead.

size back to summary

size	back to summary
public int size() Redeclares java.util.Collection.size. Returns the total number of all occurrences of all elements in this multiset. Note this method does not return the number of distinct elements in the multiset, which is given by `entrySet().size()`. Returns:int Doc from java.util.Collection.size. the number of elements in this collection Annotations @Override

public int size()

Redeclares java.util.Collection.size.

Returns the total number of all occurrences of all elements in this multiset.

Note

this method does not return the number of distinct elements in the multiset, which is given by entrySet().size().

Returns:int

Doc from java.util.Collection.size.

the number of elements in this collection

Annotations

@Override

spliterator back to summary

spliterator	back to summary
public default Spliterator<E> spliterator() Overrides default java.util.Collection.spliterator. Doc from java.util.Collection.spliterator. Creates a `Spliterator` over the elements in this collection. Implementations should document characteristic values reported by the spliterator. Such characteristic values are not required to be reported if the spliterator reports `Spliterator#SIZED` and this collection contains no elements. The default implementation should be overridden by subclasses that can return a more efficient spliterator. In order to preserve expected laziness behavior for the `stream()` and `parallelStream()` methods, spliterators should either have the characteristic of `IMMUTABLE` or `CONCURRENT`, or be late-binding. If none of these is practical, the overriding class should describe the spliterator's documented policy of binding and structural interference, and should override the `stream()` and `parallelStream()` methods to create streams using a `Supplier` of the spliterator, as in: `Stream<E> s = StreamSupport.stream(() -> spliterator(), spliteratorCharacteristics)` These requirements ensure that streams produced by the `stream()` and `parallelStream()` methods will reflect the contents of the collection as of initiation of the terminal stream operation. Returns:Spliterator<E> a `Spliterator` over the elements in this collection Annotations @Override

public default Spliterator<E> spliterator()

Overrides default java.util.Collection.spliterator.

Doc from java.util.Collection.spliterator.

Creates a Spliterator over the elements in this collection. Implementations should document characteristic values reported by the spliterator. Such characteristic values are not required to be reported if the spliterator reports Spliterator#SIZED and this collection contains no elements.

The default implementation should be overridden by subclasses that can return a more efficient spliterator. In order to preserve expected laziness behavior for the stream() and parallelStream() methods, spliterators should either have the characteristic of IMMUTABLE or CONCURRENT, or be late-binding. If none of these is practical, the overriding class should describe the spliterator's documented policy of binding and structural interference, and should override the stream() and parallelStream() methods to create streams using a Supplier of the spliterator, as in:

Stream<E> s = StreamSupport.stream(() -> spliterator(), spliteratorCharacteristics)

These requirements ensure that streams produced by the stream() and parallelStream() methods will reflect the contents of the collection as of initiation of the terminal stream operation.

Returns:Spliterator<E>

a Spliterator over the elements in this collection

Annotations

@Override

toString back to summary

toString	back to summary
public String toString() It is recommended, though not mandatory, that this method return the result of invoking `toString` on the `entrySet`, yielding a result such as `[a x 3, c, d x 2, e]`. Annotations @Override

public String toString()

It is recommended, though not mandatory, that this method return the result of invoking toString on the entrySet, yielding a result such as [a x 3, c, d x 2, e].

Annotations

@Override

public Interface Multiset<E extends @Nullable Object>

Implementations

Nested and Inner Type Summary

Method Summary

Method Detail

public Interface Multiset.Entry<E extends @Nullable Object>

Method Summary

Method Detail

Modifier and Type	Method and Description
public boolean	equals(Object o) Returns `true` if the given object is also a multiset entry and the two entries represent the same element and count.
public int	Returns: the count of the element; never negative getCount() Returns the count of the associated element in the underlying multiset.
public E	Returns: the element corresponding to this entry getElement() Returns the multiset element corresponding to this entry.
public int	hashCode() The hash code of a multiset entry for element `element` and count `count` is defined as: `((element == null) ?`
public String	toString() Returns the canonical string representation of this entry, defined as follows.