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    import org.apache.commons.collections.Transformer;
023    
024    /**
025     * Decorates another <code>SortedBag</code> to transform objects that are added.
026     * <p>
027     * The add methods are affected by this class.
028     * Thus objects must be removed or searched for using their transformed form.
029     * For example, if the transformation converts Strings to Integers, you must
030     * use the Integer form to remove objects.
031     * <p>
032     * This class is Serializable from Commons Collections 3.1.
033     *
034     * @since Commons Collections 3.0
035     * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
036     * 
037     * @author Stephen Colebourne
038     */
039    public class TransformedSortedBag
040            extends TransformedBag implements SortedBag {
041    
042        /** Serialization version */
043        private static final long serialVersionUID = -251737742649401930L;
044    
045        /**
046         * Factory method to create a transforming sorted bag.
047         * <p>
048         * If there are any elements already in the bag being decorated, they
049         * are NOT transformed.
050         * 
051         * @param bag  the bag to decorate, must not be null
052         * @param transformer  the transformer to use for conversion, must not be null
053         * @return a new transformed SortedBag
054         * @throws IllegalArgumentException if bag or transformer is null
055         */
056        public static SortedBag decorate(SortedBag bag, Transformer transformer) {
057            return new TransformedSortedBag(bag, transformer);
058        }
059        
060        //-----------------------------------------------------------------------
061        /**
062         * Constructor that wraps (not copies).
063         * <p>
064         * If there are any elements already in the bag being decorated, they
065         * are NOT transformed.
066         * 
067         * @param bag  the bag to decorate, must not be null
068         * @param transformer  the transformer to use for conversion, must not be null
069         * @throws IllegalArgumentException if bag or transformer is null
070         */
071        protected TransformedSortedBag(SortedBag bag, Transformer transformer) {
072            super(bag, transformer);
073        }
074    
075        /**
076         * Gets the decorated bag.
077         * 
078         * @return the decorated bag
079         */
080        protected SortedBag getSortedBag() {
081            return (SortedBag) collection;
082        }
083    
084        //-----------------------------------------------------------------------
085        public Object first() {
086            return getSortedBag().first();
087        }
088    
089        public Object last() {
090            return getSortedBag().last();
091        }
092    
093        public Comparator comparator() {
094            return getSortedBag().comparator();
095        }
096    
097    }