Coverage Summary for Class: JdkBackedImmutableMultiset (com.google.common.collect)

1 /*
2  * Copyright (C) 2018 The Guava Authors
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5  * in compliance with the License. You may obtain a copy of the License at
6  *
7  * http://www.apache.org/licenses/LICENSE-2.0
8  *
9  * Unless required by applicable law or agreed to in writing, software distributed under the License
10  * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11  * or implied. See the License for the specific language governing permissions and limitations under
12  * the License.
13  */
14 
15 package com.google.common.collect;
16 
17 import static com.google.common.base.Preconditions.checkNotNull;
18 
19 import com.google.common.annotations.GwtCompatible;
20 import com.google.common.primitives.Ints;
21 import java.util.Collection;
22 import java.util.Map;
23 import javax.annotation.CheckForNull;
24 
25 /**
26  * An implementation of ImmutableMultiset backed by a JDK Map and a list of entries. Used to protect
27  * against hash flooding attacks.
28  *
29  * @author Louis Wasserman
30  */
31 @GwtCompatible
32 @ElementTypesAreNonnullByDefault
33 final class JdkBackedImmutableMultiset<E> extends ImmutableMultiset<E> {
34   private final Map<E, Integer> delegateMap;
35   private final ImmutableList<Entry<E>> entries;
36   private final long size;
37 
38   static <E> ImmutableMultiset<E> create(Collection<? extends Entry<? extends E>> entries) {
39     @SuppressWarnings("unchecked")
40     Entry<E>[] entriesArray = entries.toArray(new Entry[0]);
41     Map<E, Integer> delegateMap = Maps.newHashMapWithExpectedSize(entriesArray.length);
42     long size = 0;
43     for (int i = 0; i < entriesArray.length; i++) {
44       Entry<E> entry = entriesArray[i];
45       int count = entry.getCount();
46       size += count;
47       E element = checkNotNull(entry.getElement());
48       delegateMap.put(element, count);
49       if (!(entry instanceof Multisets.ImmutableEntry)) {
50         entriesArray[i] = Multisets.immutableEntry(element, count);
51       }
52     }
53     return new JdkBackedImmutableMultiset<>(
54         delegateMap, ImmutableList.asImmutableList(entriesArray), size);
55   }
56 
57   private JdkBackedImmutableMultiset(
58       Map<E, Integer> delegateMap, ImmutableList<Entry<E>> entries, long size) {
59     this.delegateMap = delegateMap;
60     this.entries = entries;
61     this.size = size;
62   }
63 
64   @Override
65   public int count(@CheckForNull Object element) {
66     return delegateMap.getOrDefault(element, 0);
67   }
68 
69   @CheckForNull private transient ImmutableSet<E> elementSet;
70 
71   @Override
72   public ImmutableSet<E> elementSet() {
73     ImmutableSet<E> result = elementSet;
74     return (result == null) ? elementSet = new ElementSet<E>(entries, this) : result;
75   }
76 
77   @Override
78   Entry<E> getEntry(int index) {
79     return entries.get(index);
80   }
81 
82   @Override
83   boolean isPartialView() {
84     return false;
85   }
86 
87   @Override
88   public int size() {
89     return Ints.saturatedCast(size);
90   }
91 }