Package org.apache.commons.collections.bag

Class PredicatedBag

  • All Implemented Interfaces:
    Serializable, Iterable, 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 14:33:15 +0200 (Thu, 10 Apr 2008) $
    Author:
    Stephen Colebourne, Paul Jack
    See Also:
    Serialized Form

    • 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:
        IllegalArgumentException - if bag or predicate is null
        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:
        IllegalArgumentException - if bag or predicate is null
        IllegalArgumentException - if the bag contains invalid elements

      • getBag

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

      • add

        public boolean add​(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​(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 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​(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