Package org.apache.commons.collections.collection

Class PredicatedCollection

  • All Implemented Interfaces:
    Serializable, Iterable, Collection
    Direct Known Subclasses:
    PredicatedBag, PredicatedBuffer, PredicatedList, PredicatedSet
    public class PredicatedCollection
extends AbstractSerializableCollectionDecorator
    Decorates another Collection to validate that additions match a specified predicate.

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

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

    Collection coll = PredicatedCollection.decorate(new ArrayList(), 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

    • Field Detail

      • predicate

        protected final Predicate predicate
        The predicate to use

    • Constructor Detail

      • PredicatedCollection

        protected PredicatedCollection​(Collection coll,
                               Predicate predicate)
        Constructor that wraps (not copies).

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

        Parameters:
        coll - the collection to decorate, must not be null
        predicate - the predicate to use for validation, must not be null
        Throws:
        IllegalArgumentException - if collection or predicate is null
        IllegalArgumentException - if the collection contains invalid elements

    • Method Detail

      • decorate

        public static Collection decorate​(Collection coll,
                                  Predicate predicate)
        Factory method to create a predicated (validating) collection.

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

        Parameters:
        coll - the collection to decorate, must not be null
        predicate - the predicate to use for validation, must not be null
        Returns:
        a new predicated collection
        Throws:
        IllegalArgumentException - if collection or predicate is null
        IllegalArgumentException - if the collection contains invalid elements

      • validate

        protected void validate​(Object object)
        Validates the object being added to ensure it matches the predicate.

        The predicate itself should not throw an exception, but return false to indicate that the object cannot be added.

        Parameters:
        object - the object being added
        Throws:
        IllegalArgumentException - if the add is invalid

      • add

        public boolean add​(Object object)
        Override to validate the object being added to ensure it matches the predicate.
        Specified by:
        add in interface Collection
        Overrides:
        add in class AbstractCollectionDecorator
        Parameters:
        object - the object being added
        Returns:
        the result of adding to the underlying collection
        Throws:
        IllegalArgumentException - if the add is invalid

      • addAll

        public boolean addAll​(Collection coll)
        Override to validate the objects being added to ensure they match the predicate. If any one fails, no update is made to the underlying collection.
        Specified by:
        addAll in interface Collection
        Overrides:
        addAll in class AbstractCollectionDecorator
        Parameters:
        coll - the collection being added
        Returns:
        the result of adding to the underlying collection
        Throws:
        IllegalArgumentException - if the add is invalid