1 /* 2 * Copyright (c) 2021, 2023, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.util; 27 28 /** 29 * A collection that is both a {@link SequencedCollection} and a {@link Set}. As such, 30 * it can be thought of either as a {@code Set} that also has a well-defined 31 * <a href="SequencedCollection.html#encounter">encounter order</a>, or as a 32 * {@code SequencedCollection} that also has unique elements. 33 * <p> 34 * This interface has the same requirements on the {@code equals} and {@code hashCode} 35 * methods as defined by {@link Set#equals Set.equals} and {@link Set#hashCode Set.hashCode}. 36 * Thus, a {@code Set} and a {@code SequencedSet} will compare equals if and only 37 * if they have equal elements, irrespective of ordering. 38 * <p> 39 * {@code SequencedSet} defines the {@link #reversed} method, which provides a 40 * reverse-ordered <a href="Collection.html#view">view</a> of this set. The only difference 41 * from the {@link SequencedCollection#reversed SequencedCollection.reversed} method is 42 * that the return type of {@code SequencedSet.reversed} is {@code SequencedSet}. 43 * <p> 44 * This class is a member of the 45 * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework"> 46 * Java Collections Framework</a>. 47 * 48 * @param <E> the type of elements in this sequenced set 49 * @since 21 50 */ 51 public interface SequencedSet<E> extends SequencedCollection<E>, Set<E> { 52 /** 53 * {@inheritDoc} 54 * 55 * @return a reverse-ordered view of this collection, as a {@code SequencedSet} 56 */ reversed()57 SequencedSet<E> reversed(); 58 } 59