1/*
2 * Copyright (C) 2011 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
15package com.google.common.collect;
16
17import static com.google.common.base.Preconditions.checkNotNull;
18
19import java.util.Collection;
20import java.util.Comparator;
21
22import javax.annotation.Nullable;
23
24/**
25 * An empty immutable sorted multiset.
26 *
27 * @author Louis Wasserman
28 */
29@SuppressWarnings("serial") // Uses writeReplace, not default serialization
30final class EmptyImmutableSortedMultiset<E> extends ImmutableSortedMultiset<E> {
31  private final ImmutableSortedSet<E> elementSet;
32
33  EmptyImmutableSortedMultiset(Comparator<? super E> comparator) {
34    this.elementSet = ImmutableSortedSet.emptySet(comparator);
35  }
36
37  @Override
38  public Entry<E> firstEntry() {
39    return null;
40  }
41
42  @Override
43  public Entry<E> lastEntry() {
44    return null;
45  }
46
47  @Override
48  public int count(@Nullable Object element) {
49    return 0;
50  }
51
52  @Override
53  public boolean containsAll(Collection<?> targets) {
54    return targets.isEmpty();
55  }
56
57  @Override
58  public int size() {
59    return 0;
60  }
61
62  @Override
63  public ImmutableSortedSet<E> elementSet() {
64    return elementSet;
65  }
66
67  @Override
68  Entry<E> getEntry(int index) {
69    throw new AssertionError("should never be called");
70  }
71
72  @Override
73  public ImmutableSortedMultiset<E> headMultiset(E upperBound, BoundType boundType) {
74    checkNotNull(upperBound);
75    checkNotNull(boundType);
76    return this;
77  }
78
79  @Override
80  public ImmutableSortedMultiset<E> tailMultiset(E lowerBound, BoundType boundType) {
81    checkNotNull(lowerBound);
82    checkNotNull(boundType);
83    return this;
84  }
85
86  @Override
87  public UnmodifiableIterator<E> iterator() {
88    return Iterators.emptyIterator();
89  }
90
91  @Override
92  public boolean equals(@Nullable Object object) {
93    if (object instanceof Multiset) {
94      Multiset<?> other = (Multiset<?>) object;
95      return other.isEmpty();
96    }
97    return false;
98  }
99
100  @Override
101  boolean isPartialView() {
102    return false;
103  }
104
105  @Override
106  int copyIntoArray(Object[] dst, int offset) {
107    return offset;
108  }
109
110  @Override
111  public ImmutableList<E> asList() {
112    return ImmutableList.of();
113  }
114}
115