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 * <p>
033 * One usage would be to ensure that no null entries are added to the queue.
034 * </p>
035 * <pre>Queue queue = PredicatedQueue.predicatedQueue(new UnboundedFifoQueue(), NotNullPredicate.INSTANCE);</pre>
036 *
037 * @param <E> the type of elements held in this queue
038 * @since 4.0
039 */
040public class PredicatedQueue<E> extends PredicatedCollection<E> implements Queue<E> {
041
042    /** Serialization version */
043    private static final long serialVersionUID = 2307609000539943581L;
044
045    /**
046     * Factory method to create a predicated (validating) queue.
047     * <p>
048     * If there are any elements already in the queue being decorated, they
049     * are validated.
050     *
051     * @param <E> the type of the elements in the queue
052     * @param Queue  the queue to decorate, must not be null
053     * @param predicate  the predicate to use for validation, must not be null
054     * @return a new predicated queue
055     * @throws NullPointerException if queue or predicate is null
056     * @throws IllegalArgumentException if the queue contains invalid elements
057     */
058    public static <E> PredicatedQueue<E> predicatedQueue(final Queue<E> Queue,
059                                                          final Predicate<? super E> predicate) {
060        return new PredicatedQueue<>(Queue, predicate);
061    }
062
063    /**
064     * Constructor that wraps (not copies).
065     * <p>
066     * If there are any elements already in the collection being decorated, they
067     * are validated.
068     *
069     * @param queue  the queue to decorate, must not be null
070     * @param predicate  the predicate to use for validation, must not be null
071     * @throws NullPointerException if queue or predicate is null
072     * @throws IllegalArgumentException if the Queue contains invalid elements
073     */
074    protected PredicatedQueue(final Queue<E> queue, final Predicate<? super E> predicate) {
075        super(queue, predicate);
076    }
077
078    /**
079     * Gets the queue being decorated.
080     *
081     * @return the decorated queue
082     */
083    @Override
084    protected Queue<E> decorated() {
085        return (Queue<E>) super.decorated();
086    }
087
088    @Override
089    public E element() {
090        return decorated().element();
091    }
092
093    /**
094     * Override to validate the object being added to ensure it matches
095     * the predicate.
096     *
097     * @param object  the object being added
098     * @return the result of adding to the underlying queue
099     * @throws IllegalArgumentException if the add is invalid
100     */
101    @Override
102    public boolean offer(final E object) {
103        validate(object);
104        return decorated().offer(object);
105    }
106
107    @Override
108    public E peek() {
109        return decorated().peek();
110    }
111
112    @Override
113    public E poll() {
114        return decorated().poll();
115    }
116
117    @Override
118    public E remove() {
119        return decorated().remove();
120    }
121
122}