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.util.Objects; 29 30 /** 31 * Wrapper for querying the backing map. Avoids the overhead of an 32 * {@link java.lang.ref.Reference} object. 33 * 34 * @param <T> key type 35 * 36 * @since 21 37 */ 38 final class StrongReferenceKey<T> implements ReferenceKey<T> { 39 T key; 40 41 /** 42 * Package-Protected constructor. 43 * 44 * @param key unwrapped key value 45 */ StrongReferenceKey(T key)46 StrongReferenceKey(T key) { 47 // Android-changed: Some ReferencedKeyMap methods check key for nullness (get, put, 48 // containsKey), but others (putIfAbsent) don't. Adding null check here with assumption 49 // that absence of null checks in ReferencedKeyMap was just overlooked. 50 // this.key = key; 51 this.key = Objects.requireNonNull(key); 52 } 53 54 /** 55 * {@return the unwrapped key} 56 */ 57 @Override get()58 public T get() { 59 return key; 60 } 61 62 @Override unused()63 public void unused() { 64 key = null; 65 } 66 67 @Override equals(Object obj)68 public boolean equals(Object obj) { 69 // Necessary when comparing an unwrapped key 70 if (obj instanceof ReferenceKey<?> key) { 71 obj = key.get(); 72 } 73 return Objects.equals(get(), obj); 74 } 75 76 @Override hashCode()77 public int hashCode() { 78 // Use unwrapped key hash code 79 // Android-changed: throw NPE explicitly. After unused() call this object should not be used 80 // return get().hashCode(); 81 T nonNullKey = Objects.requireNonNull(get()); 82 return nonNullKey.hashCode(); 83 } 84 85 @Override toString()86 public String toString() { 87 return this.getClass().getCanonicalName() + "#" + System.identityHashCode(this); 88 } 89 } 90