org.apache.commons.collections
public interface Bag extends Collection
Suppose you have a Bag that contains {a, a, b, c}
.
Calling getCount 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.
Since: Commons Collections 2.0
Version: $Revision: 155406 $ $Date: 2005-02-26 12:55:26 +0000 (Sat, 26 Feb 2005) $
Method Summary | |
---|---|
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.
|
If the object is already in the uniqueSet then increment its count as reported by getCount. 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.
Parameters: object the object to add
Returns: true
if the object was not already in the uniqueSet
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. Otherwise add it to the
uniqueSet and report its count as nCopies
.
Parameters: object the object to add nCopies the number of copies to add
Returns: true
if the object was not already in the uniqueSet
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 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.
Parameters: coll the collection to check against
Returns: true
if the Bag contains all the collection
Parameters: object the object to search for
Returns: the number of occurrences of the object, zero if not found
Returns: iterator over all elements in the Bag
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.
Returns: true
if this call changed the collection
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.
Parameters: object the object to remove nCopies the number of copies to remove
Returns: true
if this call changed the collection
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.
Parameters: coll the collection to remove
Returns: true
if this call changed the collection
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.
Parameters: coll the collection to retain
Returns: true
if this call changed the collection
Returns: the total size of the Bag
Uniqueness constraints are the same as those in java.util.Set.
Returns: the Set of unique Bag elements