org.apache.commons.collections.bag
Class PredicatedBag

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

All Implemented Interfaces:

java.io.Serializable, java.lang.Iterable, java.util.Collection, Bag

Direct Known 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.

Since:

Commons Collections 3.0

Version:

$Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $

Author:

Stephen Colebourne, 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 bag, Predicate predicate) Constructor that wraps (not copies).

Method Summary

boolean	add(java.lang.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(java.lang.Object object) Returns the number of occurrences (cardinality) of the given object currently in the bag.
boolean	remove(java.lang.Object object, int count) Removes nCopies copies of the specified object from the Bag.
java.util.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 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

Throws:

java.lang.IllegalArgumentException - if bag or predicate is null

java.lang.IllegalArgumentException - if the bag contains invalid elements

Method Detail

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

Throws:

java.lang.IllegalArgumentException - if bag or predicate is null

java.lang.IllegalArgumentException - if the bag contains invalid elements

getBag

protected Bag getBag()

Gets the decorated bag.

Returns:

the decorated bag

add

public boolean add(java.lang.Object 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

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(java.lang.Object 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

Parameters:

object - the object to remove

count - the number of copies to remove

Returns:

true if this call changed the collection

uniqueSet

public java.util.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

Returns:

the Set of unique Bag elements

getCount

public int getCount(java.lang.Object 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

Parameters:

object - the object to search for

Returns:

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