org.apache.commons.collections.bag

Class PredicatedBag

Implemented Interfaces:
Bag, Collection, Serializable
Known Direct Subclasses:
PredicatedSortedBag

public class PredicatedBag
extends PredicatedCollection
implements Bag

Decorates another Bag to validate that additions match a specified predicate.

This bag exists to provide validation for the decorated bag. It is normally created to decorate an empty bag. If an object cannot be added to the bag, an IllegalArgumentException is thrown.

One usage would be to ensure that no null entries are added to the bag.

Bag bag = PredicatedBag.decorate(new HashBag(), NotNullPredicate.INSTANCE);

This class is Serializable from Commons Collections 3.1.

Version:
$Revision: 1.8 $ $Date: 2004/06/03 22:02:12 $
Authors:
Stephen Colebourne
Paul Jack
Since:
Commons Collections 3.0

Field Summary

Fields inherited from class org.apache.commons.collections.collection.PredicatedCollection

predicate

Fields inherited from class org.apache.commons.collections.collection.AbstractCollectionDecorator

collection

Constructor Summary

PredicatedBag(Bag bag, Predicate predicate)
Constructor that wraps (not copies).

Method Summary

boolean
add(Object object, int count)
Adds nCopies copies of the specified object to the Bag.
static Bag
decorate(Bag bag, Predicate predicate)
Factory method to create a predicated (validating) bag.
protected Bag
getBag()
Gets the decorated bag.
int
getCount(Object object)
Returns the number of occurrences (cardinality) of the given object currently in the bag.
boolean
remove(Object object, int count)
Removes nCopies copies of the specified object from the Bag.
Set
uniqueSet()
Returns a Set of unique elements in the Bag.

Methods inherited from class org.apache.commons.collections.collection.PredicatedCollection

add, addAll, decorate, validate

Methods inherited from class org.apache.commons.collections.collection.AbstractCollectionDecorator

add, addAll, clear, contains, containsAll, equals, getCollection, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray, toString

Constructor Details

PredicatedBag

protected PredicatedBag(Bag bag,
                        Predicate predicate)
Constructor that wraps (not copies).

If there are any elements already in the bag being decorated, they are validated.

Parameters:
bag - the bag to decorate, must not be null
predicate - the predicate to use for validation, must not be null

Method Details

add

public boolean add(Object object,
                   int count)
Adds nCopies copies of the specified object to the Bag.

If the object is already in the Bag.uniqueSet() then increment its count as reported by Bag.getCount(Object). Otherwise add it to the Bag.uniqueSet() and report its count as nCopies.

Specified by:
add in interface Bag
Parameters:
object - the object to add
Returns:
true if the object was not already in the uniqueSet

decorate

public static Bag decorate(Bag bag,
                           Predicate predicate)
Factory method to create a predicated (validating) bag.

If there are any elements already in the bag being decorated, they are validated.

Parameters:
bag - the bag to decorate, must not be null
predicate - the predicate to use for validation, must not be null
Returns:
a new predicated Bag

getBag

protected Bag getBag()
Gets the decorated bag.
Returns:
the decorated bag

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.
Specified by:
getCount in interface Bag
Parameters:
object - the object to search for
Returns:
the number of occurrences of the object, zero if not found

remove

public boolean remove(Object object,
                      int count)
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.

Specified by:
remove in interface Bag
Parameters:
object - the object to remove
Returns:
true if this call changed the collection

uniqueSet

public Set uniqueSet()
Returns a Set of unique elements in the Bag.

Uniqueness constraints are the same as those in java.util.Set.

Specified by:
uniqueSet in interface Bag
Returns:
the Set of unique Bag elements

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