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>

Field Summary

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

predicate

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	PredicatedQueue(Queue<E> queue, Predicate<? super E> predicate)	Constructor that wraps (not copies).

Method Summary

Modifier and Type	Method	Description
protected Queue<E>	decorated()	Gets the queue being decorated.
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, validate

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

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

Methods inherited from class java.lang.Object

clone, equals, finalize, 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

Constructor Detail

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 Detail

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

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>