org.apache.commons.collections4.queue
Class PredicatedQueue<E>

java.lang.Object
  org.apache.commons.collections4.collection.AbstractCollectionDecorator<E>
      org.apache.commons.collections4.collection.PredicatedCollection<E>
          org.apache.commons.collections4.queue.PredicatedQueue<E>

All Implemented Interfaces:

Serializable, Iterable<E>, Collection<E>, Queue<E>

public class PredicatedQueue<E>
extends PredicatedCollection<E>
implements Queue<E>

Decorates another Queue to validate that additions match a specified predicate.

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

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

Queue queue = PredicatedQueue.predicatedQueue(new UnboundedFifoQueue(), NotNullPredicate.INSTANCE);

Since:

4.0

Version:

$Id: PredicatedQueue.java 1477765 2013-04-30 18:37:37Z tn $

See Also:

Serialized Form

PredicatedQueue

protected PredicatedQueue(Queue<E> queue,
                          Predicate<? super E> predicate)

Constructor that wraps (not copies).

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

Parameters:

queue - the queue to decorate, must not be null

predicate - the predicate to use for validation, must not be null

Throws:

IllegalArgumentException - if Queue or predicate is null

IllegalArgumentException - if the Queue contains invalid elements

predicatedQueue

public static <E> PredicatedQueue<E> predicatedQueue(Queue<E> Queue,
                                                     Predicate<? super E> predicate)

Factory method to create a predicated (validating) queue.

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

Type Parameters:

E - the type of the elements in the queue

Parameters:

Queue - the queue to decorate, must not be null

predicate - the predicate to use for validation, must not be null

Returns:

a new predicated queue

Throws:

IllegalArgumentException - if queue or predicate is null

IllegalArgumentException - if the queue contains invalid elements

decorated

protected Queue<E> decorated()

Gets the queue being decorated.

Overrides:

decorated in class AbstractCollectionDecorator<E>

Returns:

the decorated queue

offer

public boolean offer(E object)

Override to validate the object being added to ensure it matches the predicate.

Specified by:

offer in interface Queue<E>

Parameters:

object - the object being added

Returns:

the result of adding to the underlying queue

Throws:

IllegalArgumentException - if the add is invalid

poll

public E poll()

Specified by:

poll in interface Queue<E>

peek

public E peek()

Specified by:

peek in interface Queue<E>

element

public E element()

Specified by:

element in interface Queue<E>

remove

public E remove()

Specified by:

remove in interface Queue<E>