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

java.lang.Object
  extended by org.apache.commons.collections.collection.AbstractCollectionDecorator<E>
      extended by org.apache.commons.collections.collection.AbstractSerializableCollectionDecorator<E>
          extended by org.apache.commons.collections.collection.PredicatedCollection<E>
              extended by 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


Copyright © 2005-2005 Apache Software Foundation, Matt Hall, John Watkinson. All Rights Reserved.