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:

• Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.commons.collections4.collection.PredicatedCollection

PredicatedCollection.Builder<E>

Method Summary

Modifier and Type	Method	Description
E	element()
boolean	offer(E object)	Override to validate the object being added to ensure it matches the predicate.
E	peek()
E	poll()
static <E> PredicatedQueue<E>	predicatedQueue(Queue<E> Queue, Predicate<? super E> predicate)	Factory method to create a predicated (validating) queue.
E	remove()

Methods inherited from class org.apache.commons.collections4.collection.PredicatedCollection

add, addAll, builder, notNullBuilder, predicatedCollection

Methods inherited from class org.apache.commons.collections4.collection.AbstractCollectionDecorator

clear, contains, containsAll, isEmpty, iterator, remove, removeAll, removeIf, retainAll, size, toArray, toArray, toString

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, parallelStream, remove, removeAll, removeIf, retainAll, size, spliterator, stream, toArray, toArray, toArray

Methods inherited from interface java.lang.Iterable

forEach

Methods inherited from interface java.util.Queue

add

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

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>