@GwtCompatible public abstract class ForwardingMultiset<E> extends ForwardingCollection<E> implements Multiset<E>
Warning: The methods of ForwardingMultiset forward
indiscriminately to the methods of the delegate. For example,
overriding add(Object, int) alone will not change the
behavior of ForwardingCollection.add(Object), which can lead to unexpected behavior. In
this case, you should override add(Object) as well, either providing
your own implementation, or delegating to the provided standardAdd
method.
default method warning: This class does not forward calls to default methods. Instead, it inherits their default implementations. When those implementations
invoke methods, they invoke methods on the ForwardingMultiset.
The standard methods and any collection views they return are not
guaranteed to be thread-safe, even when all of the methods that they depend
on are thread-safe.
| Modifier and Type | Class and Description |
|---|---|
protected class |
ForwardingMultiset.StandardElementSet
A sensible implementation of
Multiset.elementSet() in terms of the
following methods: ForwardingCollection.clear(), ForwardingCollection.contains(java.lang.Object), ForwardingCollection.containsAll(java.util.Collection<?>),
count(java.lang.Object), ForwardingCollection.isEmpty(), the
Set.size() and Set.iterator() methods of entrySet(), and remove(Object,
int). |
Multiset.Entry<E>| Modifier | Constructor and Description |
|---|---|
protected |
ForwardingMultiset()
Constructor for use by subclasses.
|
| Modifier and Type | Method and Description |
|---|---|
int |
add(E element,
int occurrences)
Adds a number of occurrences of an element to this multiset.
|
int |
count(Object element)
Returns the number of occurrences of an element in this multiset (the count of the
element).
|
protected abstract Multiset<E> |
delegate()
Returns the backing delegate instance that methods are forwarded to.
|
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.
|
int |
remove(Object element,
int occurrences)
Removes a number of occurrences of the specified element from this multiset.
|
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. |
protected boolean |
standardAdd(E element)
A sensible definition of
ForwardingCollection.add(Object) in terms of add(Object, int). |
protected boolean |
standardAddAll(Collection<? extends E> elementsToAdd)
A sensible definition of
ForwardingCollection.addAll(Collection) in terms of ForwardingCollection.add(Object) and add(Object, int). |
protected void |
standardClear()
A sensible definition of
ForwardingCollection.clear() in terms of the iterator
method of entrySet(). |
protected boolean |
standardContains(Object object)
A sensible definition of
ForwardingCollection.contains(java.lang.Object) in terms of count(java.lang.Object). |
protected int |
standardCount(Object object)
A sensible, albeit inefficient, definition of
count(java.lang.Object) in terms of
entrySet(). |
protected boolean |
standardEquals(Object object)
A sensible, albeit inefficient, definition of
equals(java.lang.Object) in terms of
entrySet().size() and count(java.lang.Object). |
protected int |
standardHashCode()
A sensible definition of
hashCode() as entrySet().hashCode()
. |
protected Iterator<E> |
standardIterator()
A sensible definition of
ForwardingCollection.iterator() in terms of entrySet()
and ForwardingCollection.remove(Object). |
protected boolean |
standardRemove(Object element)
A sensible definition of
ForwardingCollection.remove(Object) in terms of remove(Object, int). |
protected boolean |
standardRemoveAll(Collection<?> elementsToRemove)
A sensible definition of
ForwardingCollection.removeAll(java.util.Collection<?>) in terms of the removeAll method of elementSet(). |
protected boolean |
standardRetainAll(Collection<?> elementsToRetain)
A sensible definition of
ForwardingCollection.retainAll(java.util.Collection<?>) in terms of the retainAll method of elementSet(). |
protected int |
standardSetCount(E element,
int count)
A sensible definition of
setCount(Object, int) in terms of count(Object), add(Object, int), and remove(Object,
int). |
protected boolean |
standardSetCount(E element,
int oldCount,
int newCount)
A sensible definition of
setCount(Object, int, int) in terms of
count(Object) and setCount(Object, int). |
protected int |
standardSize()
A sensible, albeit inefficient, definition of
ForwardingCollection.size() in terms of
entrySet(). |
protected String |
standardToString()
A sensible definition of
ForwardingObject.toString() as entrySet().toString()
. |
add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, standardContainsAll, standardIsEmpty, standardToArray, standardToArray, toArray, toArraytoStringclone, finalize, getClass, notify, notifyAll, toString, wait, wait, waitadd, contains, containsAll, iterator, remove, removeAll, retainAll, size, toStringaddAll, clear, isEmpty, parallelStream, removeIf, spliterator, stream, toArray, toArrayprotected ForwardingMultiset()
protected abstract Multiset<E> delegate()
ForwardingObjectForwardingSet.delegate(). Concrete subclasses override this method to supply
the instance being decorated.delegate in class ForwardingCollection<E>public int count(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.
public int add(E element, int occurrences)
Multisetoccurrences == 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 int remove(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 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 Set<Multiset.Entry<E>> entrySet()
MultisetMultiset.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.
public boolean equals(@Nullable Object object)
java.lang.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.
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()
java.lang.ObjectHashMap.
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.)
hashCode in interface Multiset<E>hashCode in interface Collection<E>hashCode in class ObjectObject.equals(java.lang.Object),
System.identityHashCode(java.lang.Object)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 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.protected boolean standardContains(@Nullable Object object)
ForwardingCollection.contains(java.lang.Object) in terms of count(java.lang.Object). If
you override count(java.lang.Object), you may wish to override ForwardingCollection.contains(java.lang.Object) to
forward to this implementation.standardContains in class ForwardingCollection<E>protected void standardClear()
ForwardingCollection.clear() in terms of the iterator
method of entrySet(). If you override entrySet(), you may
wish to override ForwardingCollection.clear() to forward to this implementation.standardClear in class ForwardingCollection<E>@Beta protected int standardCount(@Nullable Object object)
count(java.lang.Object) in terms of
entrySet(). If you override entrySet(), you may wish to
override count(java.lang.Object) to forward to this implementation.protected boolean standardAdd(E element)
ForwardingCollection.add(Object) in terms of add(Object, int). If you override add(Object, int), you may
wish to override ForwardingCollection.add(Object) to forward to this implementation.@Beta protected boolean standardAddAll(Collection<? extends E> elementsToAdd)
ForwardingCollection.addAll(Collection) in terms of ForwardingCollection.add(Object) and add(Object, int). If you override either of
these methods, you may wish to override ForwardingCollection.addAll(Collection) to
forward to this implementation.standardAddAll in class ForwardingCollection<E>protected boolean standardRemove(Object element)
ForwardingCollection.remove(Object) in terms of remove(Object, int). If you override remove(Object, int), you
may wish to override ForwardingCollection.remove(Object) to forward to this
implementation.standardRemove in class ForwardingCollection<E>protected boolean standardRemoveAll(Collection<?> elementsToRemove)
ForwardingCollection.removeAll(java.util.Collection<?>) in terms of the removeAll method of elementSet(). If you override elementSet(), you may wish to override ForwardingCollection.removeAll(java.util.Collection<?>) to forward to
this implementation.standardRemoveAll in class ForwardingCollection<E>protected boolean standardRetainAll(Collection<?> elementsToRetain)
ForwardingCollection.retainAll(java.util.Collection<?>) in terms of the retainAll method of elementSet(). If you override elementSet(), you may wish to override ForwardingCollection.retainAll(java.util.Collection<?>) to forward to
this implementation.standardRetainAll in class ForwardingCollection<E>protected int standardSetCount(E element, int count)
setCount(Object, int) in terms of count(Object), add(Object, int), and remove(Object,
int). entrySet(). If you override any of these methods, you may
wish to override setCount(Object, int) to forward to this
implementation.protected boolean standardSetCount(E element, int oldCount, int newCount)
setCount(Object, int, int) in terms of
count(Object) and setCount(Object, int). If you override
either of these methods, you may wish to override setCount(Object,
int, int) to forward to this implementation.protected Iterator<E> standardIterator()
ForwardingCollection.iterator() in terms of entrySet()
and ForwardingCollection.remove(Object). If you override either of these methods, you
may wish to override ForwardingCollection.iterator() to forward to this implementation.protected int standardSize()
ForwardingCollection.size() in terms of
entrySet(). If you override entrySet(), you may wish to
override ForwardingCollection.size() to forward to this implementation.protected boolean standardEquals(@Nullable Object object)
equals(java.lang.Object) in terms of
entrySet().size() and count(java.lang.Object). If you override either of
these methods, you may wish to override equals(java.lang.Object) to forward to this
implementation.protected int standardHashCode()
hashCode() as entrySet().hashCode()
. If you override entrySet(), you may wish to override hashCode() to forward to this implementation.protected String standardToString()
ForwardingObject.toString() as entrySet().toString()
. If you override entrySet(), you may wish to override ForwardingObject.toString() to forward to this implementation.standardToString in class ForwardingCollection<E>Copyright © 2010–2017. All rights reserved.