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
17package com.google.common.collect;
18
19import static com.google.common.collect.CollectPreconditions.checkEntryNotNull;
20
21import com.google.common.annotations.GwtIncompatible;
22
23import javax.annotation.Nullable;
24
25/**
26 * Implementation of {@code Map.Entry} for {@link ImmutableMap} that adds extra methods to traverse
27 * hash buckets for the key and the value. This allows reuse in {@link RegularImmutableMap} and
28 * {@link RegularImmutableBiMap}, which don't have to recopy the entries created by their
29 * {@code Builder} implementations.
30 *
31 * @author Louis Wasserman
32 */
33@GwtIncompatible("unnecessary")
34abstract class ImmutableMapEntry<K, V> extends ImmutableEntry<K, V> {
35  ImmutableMapEntry(K key, V value) {
36    super(key, value);
37    checkEntryNotNull(key, value);
38  }
39
40  ImmutableMapEntry(ImmutableMapEntry<K, V> contents) {
41    super(contents.getKey(), contents.getValue());
42    // null check would be redundant
43  }
44
45  @Nullable
46  abstract ImmutableMapEntry<K, V> getNextInKeyBucket();
47
48  @Nullable
49  abstract ImmutableMapEntry<K, V> getNextInValueBucket();
50
51  static final class TerminalEntry<K, V> extends ImmutableMapEntry<K, V> {
52    TerminalEntry(ImmutableMapEntry<K, V> contents) {
53      super(contents);
54    }
55
56    TerminalEntry(K key, V value) {
57      super(key, value);
58    }
59
60    @Override
61    @Nullable
62    ImmutableMapEntry<K, V> getNextInKeyBucket() {
63      return null;
64    }
65
66    @Override
67    @Nullable
68    ImmutableMapEntry<K, V> getNextInValueBucket() {
69      return null;
70    }
71  }
72}
73