1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * https://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.collections4;
18
19 import java.util.Comparator;
20
21 /**
22 * Defines a type of {@code MultiSet} that maintains a sorted order among
23 * its unique representative members.
24 *
25 * @param <E> The type held in the multiset
26 * @since 4.6.0
27 */
28 public interface SortedMultiSet<E> extends MultiSet<E> {
29
30 /**
31 * Returns the comparator associated with this sorted multiset, or null
32 * if it uses its elements' natural ordering.
33 *
34 * @return The comparator in use, or null if natural ordering.
35 */
36 Comparator<? super E> comparator();
37
38 /**
39 * Returns the first (lowest) member.
40 *
41 * @return The first element in the sorted multiset.
42 */
43 E first();
44
45 /**
46 * Returns the last (highest) member.
47 *
48 * @return The last element in the sorted multiset.
49 */
50 E last();
51
52 }