@GwtCompatible public abstract class ForwardingMultiset<E> extends ForwardingCollection<E> implements Multiset<E>
A multiset which forwards all its method calls to another multiset. Subclasses should override one or more methods to modify the behavior of the backing multiset as desired per the decorator pattern.
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.
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)
Compares the specified object with this multiset for equality.
|
int |
hashCode()
Returns the hash code for this multiset.
|
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
ForwardingCollection.size() 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, toStringaddAll, clear, isEmpty, parallelStream, removeIf, size, spliterator, stream, toArray, toArrayprotected ForwardingMultiset()
Constructor for use by subclasses.
protected abstract Multiset<E> delegate()
ForwardingObjectReturns the backing delegate instance that methods are forwarded to. Abstract subclasses generally override this method with an abstract method that has a more specific return type, such as ForwardingSet.delegate(). Concrete subclasses override this method to supply the instance being decorated.
delegate in class ForwardingCollection<E>public int count(Object element)
MultisetReturns the number of occurrences of an element in this multiset (the count of the element). Note that for an Object.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)
MultisetAdds a number of occurrences of an element to this multiset. Note that if 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 int remove(Object element, int occurrences)
MultisetRemoves 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).
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()
MultisetReturns 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().
elementSet in interface Multiset<E>public Set<Multiset.Entry<E>> entrySet()
MultisetReturns 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 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)
MultisetCompares 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.
public int hashCode()
MultisetReturns 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.
public int setCount(E element, int count)
MultisetAdds or removes the necessary occurrences of an element such that the element attains the desired count.
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)
MultisetConditionally 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. 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)
A sensible definition of 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()
A sensible definition of 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)
A sensible, albeit inefficient, definition of 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)
A sensible definition of 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)
A sensible definition of 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)
A sensible definition of 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)
A sensible definition of 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)
A sensible definition of 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)
A sensible definition of 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)
A sensible definition of 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()
A sensible definition of 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()
A sensible, albeit inefficient, definition of 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)
A sensible, albeit inefficient, definition of ForwardingCollection.size() in terms of entrySet().size() and count(java.lang.Object). If you override either of these methods, you may wish to override ForwardingCollection.size() to forward to this implementation.
protected int standardHashCode()
A sensible definition of hashCode() as entrySet().hashCode() . If you override entrySet(), you may wish to override hashCode() to forward to this implementation.
protected String standardToString()
A sensible definition of 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>