    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} that maintains a sorted order among
    023 * its unique representative members.
    024 *
    025 * @param <E> the type of elements in this bag
    026 * @since 2.0
    027 */
    028public interface SortedBag<E> extends Bag<E> {
    029
    030    /**
    031     * Returns the comparator associated with this sorted set, or null
    032     * if it uses its elements' natural ordering.
    033     *
    034     * @return the comparator in use, or null if natural ordering
    035     */
    036    Comparator<? super E> comparator();
    037
    038    /**
    039     * Returns the first (lowest) member.
    040     *
    041     * @return the first element in the sorted bag
    042     */
    043    E first();
    044
    045    /**
    046     * Returns the last (highest) member.
    047     *
    048     * @return the last element in the sorted bag
    049     */
    050    E last();
    051
    052}