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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections4.queue;
import java.util.Queue;
import org.apache.commons.collections4.Predicate;
import org.apache.commons.collections4.collection.PredicatedCollection;
/**
* Decorates another {@link 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);
*
* @param the type of elements held in this queue
* @since 4.0
*/
public class PredicatedQueue extends PredicatedCollection implements Queue {
/** Serialization version */
private static final long serialVersionUID = 2307609000539943581L;
/**
* Factory method to create a predicated (validating) queue.
*
* If there are any elements already in the queue being decorated, they
* are validated.
*
* @param the type of the elements in the queue
* @param Queue the queue to decorate, must not be null
* @param predicate the predicate to use for validation, must not be null
* @return a new predicated queue
* @throws NullPointerException if queue or predicate is null
* @throws IllegalArgumentException if the queue contains invalid elements
*/
public static PredicatedQueue predicatedQueue(final Queue Queue,
final Predicate predicate) {
return new PredicatedQueue<>(Queue, predicate);
}
//-----------------------------------------------------------------------
/**
* Constructor that wraps (not copies).
*
* If there are any elements already in the collection being decorated, they
* are validated.
*
* @param queue the queue to decorate, must not be null
* @param predicate the predicate to use for validation, must not be null
* @throws NullPointerException if queue or predicate is null
* @throws IllegalArgumentException if the Queue contains invalid elements
*/
protected PredicatedQueue(final Queue queue, final Predicate predicate) {
super(queue, predicate);
}
/**
* Gets the queue being decorated.
*
* @return the decorated queue
*/
@Override
protected Queue decorated() {
return (Queue) super.decorated();
}
//-----------------------------------------------------------------------
/**
* Override to validate the object being added to ensure it matches
* the predicate.
*
* @param object the object being added
* @return the result of adding to the underlying queue
* @throws IllegalArgumentException if the add is invalid
*/
@Override
public boolean offer(final E object) {
validate(object);
return decorated().offer(object);
}
@Override
public E poll() {
return decorated().poll();
}
@Override
public E peek() {
return decorated().peek();
}
@Override
public E element() {
return decorated().element();
}
@Override
public E remove() {
return decorated().remove();
}
}