1 /* 2 * Copyright (c) 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 jdk.internal.util; 27 28 import java.lang.ref.Reference; 29 30 /** 31 * View/wrapper of keys used by the backing {@link ReferencedKeyMap}. 32 * There are two style of keys; one for entries in the backing map and 33 * one for queries to the backing map. This second style avoids the 34 * overhead of a {@link Reference} object. 35 * 36 * @param <T> key type 37 * 38 * @since 21 39 */ 40 public sealed interface ReferenceKey<T> permits StrongReferenceKey, WeakReferenceKey, SoftReferenceKey { 41 /** 42 * {@return the value of the unwrapped key} 43 */ get()44 T get(); 45 46 /** 47 * Cleanup unused key. 48 */ unused()49 void unused(); 50 51 } 52