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     */
017    package org.apache.commons.collections.bag;
018    
019    import java.util.Comparator;
020    
021    import org.apache.commons.collections.SortedBag;
022    
023    /**
024     * Decorates another <code>SortedBag</code> to provide additional behaviour.
025     * <p>
026     * Methods are forwarded directly to the decorated bag.
027     *
028     * @since Commons Collections 3.0
029     * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
030     * 
031     * @author Stephen Colebourne
032     */
033    public abstract class AbstractSortedBagDecorator
034            extends AbstractBagDecorator implements SortedBag {
035    
036        /**
037         * Constructor only used in deserialization, do not use otherwise.
038         * @since Commons Collections 3.1
039         */
040        protected AbstractSortedBagDecorator() {
041            super();
042        }
043    
044        /**
045         * Constructor that wraps (not copies).
046         * 
047         * @param bag  the bag to decorate, must not be null
048         * @throws IllegalArgumentException if list is null
049         */
050        protected AbstractSortedBagDecorator(SortedBag bag) {
051            super(bag);
052        }
053    
054        /**
055         * Gets the bag being decorated.
056         * 
057         * @return the decorated bag
058         */
059        protected SortedBag getSortedBag() {
060            return (SortedBag) getCollection();
061        }
062    
063        //-----------------------------------------------------------------------
064        public Object first() {
065            return getSortedBag().first();
066        }
067    
068        public Object last() {
069            return getSortedBag().last();
070        }
071    
072        public Comparator comparator() {
073            return getSortedBag().comparator();
074        }
075    
076    }