1 /*
2 * Copyright (C) 2013 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package com.google.common.collect;
18
19 import static com.google.common.collect.CollectPreconditions.checkEntryNotNull;
20
21 import com.google.common.annotations.GwtIncompatible;
22 import org.checkerframework.checker.nullness.qual.Nullable;
23
24 /**
25 * Implementation of {@code Entry} for {@link ImmutableMap} that adds extra methods to traverse hash
26 * buckets for the key and the value. This allows reuse in {@link RegularImmutableMap} and {@link
27 * RegularImmutableBiMap}, which don't have to recopy the entries created by their {@code Builder}
28 * implementations.
29 *
30 * <p>This base implementation has no key or value pointers, so instances of ImmutableMapEntry (but
31 * not its subclasses) can be reused when copied from one ImmutableMap to another.
32 *
33 * @author Louis Wasserman
34 */
35 @GwtIncompatible // unnecessary
36 class ImmutableMapEntry<K, V> extends ImmutableEntry<K, V> {
37 /**
38 * Creates an {@code ImmutableMapEntry} array to hold parameterized entries. The result must never
39 * be upcast back to ImmutableMapEntry[] (or Object[], etc.), or allowed to escape the class.
40 */
41 @SuppressWarnings("unchecked") // Safe as long as the javadocs are followed
42 static <K, V> ImmutableMapEntry<K, V>[] createEntryArray(int size) {
43 return new ImmutableMapEntry[size];
44 }
45
46 ImmutableMapEntry(K key, V value) {
47 super(key, value);
48 checkEntryNotNull(key, value);
49 }
50
51 ImmutableMapEntry(ImmutableMapEntry<K, V> contents) {
52 super(contents.getKey(), contents.getValue());
53 // null check would be redundant
54 }
55
56 @Nullable
57 ImmutableMapEntry<K, V> getNextInKeyBucket() {
58 return null;
59 }
60
61 @Nullable
62 ImmutableMapEntry<K, V> getNextInValueBucket() {
63 return null;
64 }
65
66 /**
67 * Returns true if this entry has no bucket links and can safely be reused as a terminal entry in
68 * a bucket in another map.
69 */
70 boolean isReusable() {
71 return true;
72 }
73
74 static class NonTerminalImmutableMapEntry<K, V> extends ImmutableMapEntry<K, V> {
75 private final transient ImmutableMapEntry<K, V> nextInKeyBucket;
76
77 NonTerminalImmutableMapEntry(K key, V value, ImmutableMapEntry<K, V> nextInKeyBucket) {
78 super(key, value);
79 this.nextInKeyBucket = nextInKeyBucket;
80 }
81
82 @Override
83 final @Nullable ImmutableMapEntry<K, V> getNextInKeyBucket() {
84 return nextInKeyBucket;
85 }
86
87 @Override
88 final boolean isReusable() {
89 return false;
90 }
91 }
92
93 static final class NonTerminalImmutableBiMapEntry<K, V>
94 extends NonTerminalImmutableMapEntry<K, V> {
95 private final transient ImmutableMapEntry<K, V> nextInValueBucket;
96
97 NonTerminalImmutableBiMapEntry(
98 K key,
99 V value,
100 ImmutableMapEntry<K, V> nextInKeyBucket,
101 ImmutableMapEntry<K, V> nextInValueBucket) {
102 super(key, value, nextInKeyBucket);
103 this.nextInValueBucket = nextInValueBucket;
104 }
105
106 @Override
107 @Nullable
108 ImmutableMapEntry<K, V> getNextInValueBucket() {
109 return nextInValueBucket;
110 }
111 }
112 }