org.apache.commons.collections4.collection

Class PredicatedCollection<E>

  • Type Parameters:
    E - the type of the elements in the collection
    All Implemented Interfaces:
    Serializable, Iterable<E>, Collection<E>
    Direct Known Subclasses:
    PredicatedBag, PredicatedList, PredicatedMultiSet, PredicatedQueue, PredicatedSet 

    public class PredicatedCollection<E>
extends AbstractCollectionDecorator<E>
    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.predicatedCollection(new ArrayList(), NotNullPredicate.INSTANCE);

    This class is Serializable from Commons Collections 3.1.

    Since:
    3.0
    See Also:
    Serialized Form

    • Field Detail

      • predicate

        protected final Predicate<? super E> predicate
        The predicate to use

    • Constructor Detail

      • PredicatedCollection

        protected PredicatedCollection(Collection<E> coll,
                               Predicate<? super E> 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:
        NullPointerException - if collection or predicate is null
        IllegalArgumentException - if the collection contains invalid elements

    • Method Detail

      • builder

        public static <E> PredicatedCollection.Builder<E> builder(Predicate<? super E> predicate)
        Returns a Builder with the given predicate.
        Type Parameters:
        E - the element type
        Parameters:
        predicate - the predicate to use
        Returns:
        a new Builder for predicated collections
        Since:
        4.1

      • notNullBuilder

        public static <E> PredicatedCollection.Builder<E> notNullBuilder()
        Returns a Builder with a NotNullPredicate.
        Type Parameters:
        E - the element type
        Returns:
        a new Builder for predicated collections that ignores null values.
        Since:
        4.1

      • predicatedCollection

        public static <T> PredicatedCollection<T> predicatedCollection(Collection<T> coll,
                                                               Predicate<? super T> predicate)
        Factory method to create a predicated (validating) collection.

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

        Type Parameters:
        T - the type of the elements in the collection
        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:
        NullPointerException - if collection or predicate is null
        IllegalArgumentException - if the collection contains invalid elements
        Since:
        4.0

      • validate

        protected void validate(E 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(E object)
        Override to validate the object being added to ensure it matches the predicate.
        Specified by:
        add in interface  Collection<E>
        Overrides:
        add in class  AbstractCollectionDecorator<E>
        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<? extends E> 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<E>
        Overrides:
        addAll in class  AbstractCollectionDecorator<E>
        Parameters:
        coll - the collection being added
        Returns:
        the result of adding to the underlying collection
        Throws:
        IllegalArgumentException - if the add is invalid