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;
018    
019    import java.util.Comparator;
020    
021    /**
022     * Defines a type of <code>Bag</code> that maintains a sorted order among
023     * its unique representative members.
024     *
025     * @since Commons Collections 2.0
026     * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
027     * 
028     * @author Chuck Burdick
029     */
030    public interface SortedBag extends Bag {
031    
032        /**
033         * Returns the comparator associated with this sorted set, or null
034         * if it uses its elements' natural ordering.
035         * 
036         * @return the comparator in use, or null if natural ordering
037         */
038        public Comparator comparator();
039    
040        /**
041         * Returns the first (lowest) member.
042         * 
043         * @return the first element in the sorted bag
044         */
045        public Object first();
046    
047        /**
048         * Returns the last (highest) member.
049         * 
050         * @return the last element in the sorted bag
051         */
052        public Object last();
053        
054    }