org.apache.commons.collections
Interface Bag
- Collection
- SortedBag
- AbstractBagDecorator, AbstractMapBag, AbstractSortedBagDecorator, DefaultMapBag, HashBag, HashBag, PredicatedBag, PredicatedSortedBag, SynchronizedBag, SynchronizedSortedBag, TransformedBag, TransformedSortedBag, TreeBag, TreeBag, UnmodifiableBag, UnmodifiableSortedBag
public interface Bag
extends Collection
Defines a collection that counts the number of times an object appears in
the 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.
$Revision: 1.18 $ $Date: 2004/05/03 15:12:20 $- Chuck Burdick
- Stephen Colebourne
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.
|
add
public boolean add(Object object)
(Violation)
Adds one copy 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 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.
object
- the object to add
true
if the object was not already in the uniqueSet
add
public boolean add(Object object,
int nCopies)
Adds
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 add
true
if the object was not already in the uniqueSet
containsAll
public boolean containsAll(Collection coll)
(Violation)
Returns
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.
coll
- the collection to check against
true
if the Bag contains all the collection
getCount
public int getCount(Object object)
Returns the number of occurrences (cardinality) of the given
object currently in the bag. If the object does not exist in the
bag, return 0.
object
- the object to search for
- the number of occurrences of the object, zero if not found
iterator
public Iterator iterator()
Returns an Iterator
over the entire set of members,
including copies due to cardinality. This iterator is fail-fast
and will not tolerate concurrent modifications.
- iterator over all elements in the Bag
remove
public boolean remove(Object object)
(Violation)
Removes all occurrences of the given object from 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.
true
if this call changed the collection
remove
public boolean remove(Object object,
int nCopies)
Removes
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 remove
true
if this call changed the collection
removeAll
public boolean removeAll(Collection coll)
(Violation)
Remove all elements represented in the given collection,
respecting cardinality. That is, if the given 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.
coll
- the collection to remove
true
if this call changed the collection
retainAll
public boolean retainAll(Collection coll)
(Violation)
Remove any members of the bag that are not in the given
collection, respecting cardinality. That is, if the given
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.
coll
- the collection to retain
true
if this call changed the collection
size
public int size()
Returns the total number of items in the bag across all types.
- the total size of the Bag
uniqueSet
public Set uniqueSet()
Returns a
Set
of unique elements in the Bag.
Uniqueness constraints are the same as those in
java.util.Set
.
- the Set of unique Bag elements
Copyright © 2001-2006 Apache Software Foundation. All Rights Reserved.