public interface Bag extends Collection
Suppose you have a Bag that contains {a, a, b, c}.
Calling getCount(Object) on a would return 2, while
calling uniqueSet() would return {a, b, c}.
NOTE: This interface violates the Collection contract.
The behavior specified in many of these methods is not the same
as the behavior specified by Collection.
The noncompliant methods are clearly marked with "(Violation)".
Exercise caution when using a bag as a Collection.
This violation resulted from the original specification of this interface. In an ideal world, the interface would be changed to fix the problems, however it has been decided to maintain backwards compatibility instead.
| Modifier and Type | Method and Description |
|---|---|
boolean |
add(Object object)
(Violation)
Adds one copy the specified object to the Bag.
|
boolean |
add(Object object,
int nCopies)
Adds
nCopies copies of the specified object to the Bag. |
boolean |
containsAll(Collection coll)
(Violation)
Returns
true if the bag contains all elements in
the given collection, respecting cardinality. |
int |
getCount(Object object)
Returns the number of occurrences (cardinality) of the given
object currently in the bag.
|
Iterator |
iterator()
Returns an
Iterator over the entire set of members,
including copies due to cardinality. |
boolean |
remove(Object object)
(Violation)
Removes all occurrences of the given object from the bag.
|
boolean |
remove(Object object,
int nCopies)
Removes
nCopies copies of the specified object from the Bag. |
boolean |
removeAll(Collection coll)
(Violation)
Remove all elements represented in the given collection,
respecting cardinality.
|
boolean |
retainAll(Collection coll)
(Violation)
Remove any members of the bag that are not in the given
collection, respecting cardinality.
|
int |
size()
Returns the total number of items in the bag across all types.
|
Set |
uniqueSet()
Returns a
Set of unique elements in the Bag. |
int getCount(Object object)
object - the object to search forboolean add(Object object)
If the object is already in the uniqueSet() then increment its
count as reported by getCount(Object). Otherwise add it to the
uniqueSet() and report its count as 1.
Since this method always increases the size of the bag,
according to the Collection.add(Object) contract, it
should always return true. Since it sometimes returns
false, this method violates the contract.
add in interface Collectionobject - the object to addtrue if the object was not already in the uniqueSetboolean add(Object object, int nCopies)
nCopies copies of the specified object to the Bag.
If the object is already in the uniqueSet() then increment its
count as reported by getCount(Object). Otherwise add it to the
uniqueSet() and report its count as nCopies.
object - the object to addnCopies - the number of copies to addtrue if the object was not already in the uniqueSetboolean remove(Object object)
This will also remove the object from the uniqueSet().
According to the Collection.remove(Object) method,
this method should only remove the first occurrence of the
given object, not all occurrences.
remove in interface Collectiontrue if this call changed the collectionboolean remove(Object object, int nCopies)
nCopies copies of the specified object from the Bag.
If the number of copies to remove is greater than the actual number of copies in the Bag, no error is thrown.
object - the object to removenCopies - the number of copies to removetrue if this call changed the collectionSet uniqueSet()
int size()
size in interface Collectionboolean containsAll(Collection coll)
true if the bag contains all elements in
the given collection, respecting cardinality. That is, if the
given collection coll contains n copies
of a given object, calling getCount(Object) on that object must
be >= n for all n in coll.
The Collection.containsAll(Collection) method specifies
that cardinality should not be respected; this method should
return true if the bag contains at least one of every object contained
in the given collection.
containsAll in interface Collectioncoll - the collection to check againsttrue if the Bag contains all the collectionboolean removeAll(Collection coll)
coll contains n copies of a given object,
the bag will have n fewer copies, assuming the bag
had at least n copies to begin with.
The Collection.removeAll(Collection) method specifies
that cardinality should not be respected; this method should
remove all occurrences of every object contained in the
given collection.
removeAll in interface Collectioncoll - the collection to removetrue if this call changed the collectionboolean retainAll(Collection coll)
coll contains n copies of a
given object and the bag has m > n copies, then
delete m - n copies from the bag. In addition, if
e is an object in the bag but
!coll.contains(e), then remove e and any
of its copies.
The Collection.retainAll(Collection) method specifies
that cardinality should not be respected; this method should
keep all occurrences of every object contained in the
given collection.
retainAll in interface Collectioncoll - the collection to retaintrue if this call changed the collectionIterator iterator()
Iterator over the entire set of members,
including copies due to cardinality. This iterator is fail-fast
and will not tolerate concurrent modifications.iterator in interface Collectioniterator in interface IterableCopyright © 2001–2015 The Apache Software Foundation. All rights reserved.