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;
018
019import 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 * @param <E> the type to iterate over
026 * @since 2.0
027 * @version $Id: SortedBag.html 972421 2015-11-14 20:00:04Z tn $
028 */
029public interface SortedBag<E> extends Bag<E> {
030
031    /**
032     * Returns the comparator associated with this sorted set, or null
033     * if it uses its elements' natural ordering.
034     *
035     * @return the comparator in use, or null if natural ordering
036     */
037    Comparator<? super E> comparator();
038
039    /**
040     * Returns the first (lowest) member.
041     *
042     * @return the first element in the sorted bag
043     */
044    E first();
045
046    /**
047     * Returns the last (highest) member.
048     *
049     * @return the last element in the sorted bag
050     */
051    E last();
052
053}