Package 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>
Type Parameters:
E - the type of elements held in this queue
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
See Also:

  • Constructor Details

    • 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:
      NullPointerException - if queue or predicate is null
      IllegalArgumentException - if the Queue contains invalid elements

  • Method Details

    • 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:
      NullPointerException - 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

    • element

      public E element()
      Specified by:
      element in interface Queue<E>

    • 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

    • peek

      public E peek()
      Specified by:
      peek in interface Queue<E>

    • poll

      public E poll()
      Specified by:
      poll in interface Queue<E>

    • remove

      public E remove()
      Specified by:
      remove in interface Queue<E>