org.apache.commons.collections.bag
Class PredicatedBag<E>

java.lang.Object
  org.apache.commons.collections.collection.AbstractCollectionDecorator<E>
      org.apache.commons.collections.collection.AbstractSerializableCollectionDecorator<E>
          org.apache.commons.collections.collection.PredicatedCollection<E>
              org.apache.commons.collections.bag.PredicatedBag<E>

All Implemented Interfaces:

Serializable, Iterable<E>, Collection<E>, Bag<E>

Direct Known Subclasses:

PredicatedSortedBag

public class PredicatedBag<E>
extends PredicatedCollection<E>
implements Bag<E>

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.

Since:

Commons Collections 3.0

Version:

$Revision: 1.1.1.1 $ $Date: 2005/05/23 04:33:29 $

Author:

Stephen Colebourne, Matt Hall, John Watkinson, Paul Jack

See Also:

Serialized Form

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

protected

PredicatedBag(Bag<E> bag, Predicate<? super E> predicate) Constructor that wraps (not copies).

Method Summary

boolean	add(E object, int count) Adds nCopies copies of the specified object to the Bag.
static <E> Bag<E>	decorate(Bag<E> bag, Predicate<? super E> predicate) Factory method to create a predicated (validating) bag.
protected Bag<E>	getBag() Gets the decorated bag.
int	getCount(E object) Returns the number of occurrences (cardinality) of the given object currently in the bag.
boolean	remove(E 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

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

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.commons.collections.Bag

add, containsAll, iterator, remove, removeAll, retainAll, size

Methods inherited from interface java.util.Collection

addAll, clear, contains, equals, hashCode, isEmpty, toArray, toArray

Constructor Detail

PredicatedBag

protected PredicatedBag(Bag<E> bag,
                        Predicate<? super E> 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

Throws:

IllegalArgumentException - if bag or predicate is null

IllegalArgumentException - if the bag contains invalid elements

Method Detail

decorate

public static <E> Bag<E> decorate(Bag<E> bag,
                                  Predicate<? super E> 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

Throws:

IllegalArgumentException - if bag or predicate is null

IllegalArgumentException - if the bag contains invalid elements

getBag

protected Bag<E> getBag()

Gets the decorated bag.

Returns:

the decorated bag

add

public boolean add(E object,
                   int count)

Description copied from interface: Bag

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<E>

Parameters:

object - the object to add

count - the number of copies to add

Returns:

true if the object was not already in the uniqueSet

remove

public boolean remove(E object,
                      int count)

Description copied from interface: Bag

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<E>

Parameters:

object - the object to remove

count - the number of copies to remove

Returns:

true if this call changed the collection

uniqueSet

public Set uniqueSet()

Description copied from interface: Bag

Returns a Set of unique elements in the Bag.

Uniqueness constraints are the same as those in Set.

Specified by:

uniqueSet in interface Bag<E>

Returns:

the Set of unique Bag elements

getCount

public int getCount(E object)

Description copied from interface: Bag

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<E>

Parameters:

object - the object to search for

Returns:

the number of occurrences of the object, zero if not found