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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(); } }





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