001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections4.queue;
018
019import java.util.Queue;
020
021import org.apache.commons.collections4.Predicate;
022import org.apache.commons.collections4.collection.PredicatedCollection;
023
024/**
025 * Decorates another {@link Queue} to validate that additions
026 * match a specified predicate.
027 * <p>
028 * This queue exists to provide validation for the decorated queue.
029 * It is normally created to decorate an empty queue.
030 * If an object cannot be added to the queue, an IllegalArgumentException is thrown.
031 * <p>
032 * One usage would be to ensure that no null entries are added to the queue.
033 * <pre>Queue queue = PredicatedQueue.predicatedQueue(new UnboundedFifoQueue(), NotNullPredicate.INSTANCE);</pre>
034 *
035 * @since 4.0
036 * @version $Id: PredicatedQueue.html 972421 2015-11-14 20:00:04Z tn $
037 */
038public class PredicatedQueue<E> extends PredicatedCollection<E> implements Queue<E> {
039
040    /** Serialization version */
041    private static final long serialVersionUID = 2307609000539943581L;
042
043    /**
044     * Factory method to create a predicated (validating) queue.
045     * <p>
046     * If there are any elements already in the queue being decorated, they
047     * are validated.
048     *
049     * @param <E> the type of the elements in the queue
050     * @param Queue  the queue to decorate, must not be null
051     * @param predicate  the predicate to use for validation, must not be null
052     * @return a new predicated queue
053     * @throws IllegalArgumentException if queue or predicate is null
054     * @throws IllegalArgumentException if the queue contains invalid elements
055     */
056    public static <E> PredicatedQueue<E> predicatedQueue(final Queue<E> Queue,
057                                                          final Predicate<? super E> predicate) {
058        return new PredicatedQueue<E>(Queue, predicate);
059    }
060
061    //-----------------------------------------------------------------------
062    /**
063     * Constructor that wraps (not copies).
064     * <p>
065     * If there are any elements already in the collection being decorated, they
066     * are validated.
067     *
068     * @param queue  the queue to decorate, must not be null
069     * @param predicate  the predicate to use for validation, must not be null
070     * @throws IllegalArgumentException if Queue or predicate is null
071     * @throws IllegalArgumentException if the Queue contains invalid elements
072     */
073    protected PredicatedQueue(final Queue<E> queue, final Predicate<? super E> predicate) {
074        super(queue, predicate);
075    }
076
077    /**
078     * Gets the queue being decorated.
079     *
080     * @return the decorated queue
081     */
082    @Override
083    protected Queue<E> decorated() {
084        return (Queue<E>) super.decorated();
085    }
086
087    //-----------------------------------------------------------------------
088
089    /**
090     * Override to validate the object being added to ensure it matches
091     * the predicate.
092     *
093     * @param object  the object being added
094     * @return the result of adding to the underlying queue
095     * @throws IllegalArgumentException if the add is invalid
096     */
097    public boolean offer(final E object) {
098        validate(object);
099        return decorated().offer(object);
100    }
101
102    public E poll() {
103        return decorated().poll();
104    }
105
106    public E peek() {
107        return decorated().peek();
108    }
109
110    public E element() {
111        return decorated().element();
112    }
113
114    public E remove() {
115        return decorated().remove();
116    }
117
118}