1/*
2 * Copyright (C) 2008 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 com.google.common.annotations.GwtCompatible;
20import com.google.common.annotations.GwtIncompatible;
21
22import java.util.Collection;
23import java.util.Comparator;
24import java.util.NoSuchElementException;
25import java.util.Set;
26
27import javax.annotation.Nullable;
28
29/**
30 * An empty immutable sorted set.
31 *
32 * @author Jared Levy
33 */
34@GwtCompatible(serializable = true, emulated = true)
35@SuppressWarnings("serial") // uses writeReplace(), not default serialization
36class EmptyImmutableSortedSet<E> extends ImmutableSortedSet<E> {
37  EmptyImmutableSortedSet(Comparator<? super E> comparator) {
38    super(comparator);
39  }
40
41  @Override
42  public int size() {
43    return 0;
44  }
45
46  @Override public boolean isEmpty() {
47    return true;
48  }
49
50  @Override public boolean contains(@Nullable Object target) {
51    return false;
52  }
53
54  @Override public boolean containsAll(Collection<?> targets) {
55    return targets.isEmpty();
56  }
57
58  @Override public UnmodifiableIterator<E> iterator() {
59    return Iterators.emptyIterator();
60  }
61
62  @GwtIncompatible("NavigableSet")
63  @Override public UnmodifiableIterator<E> descendingIterator() {
64    return Iterators.emptyIterator();
65  }
66
67  @Override boolean isPartialView() {
68    return false;
69  }
70
71  @Override public ImmutableList<E> asList() {
72    return ImmutableList.of();
73  }
74
75  @Override
76  int copyIntoArray(Object[] dst, int offset) {
77    return offset;
78  }
79
80  @Override public boolean equals(@Nullable Object object) {
81    if (object instanceof Set) {
82      Set<?> that = (Set<?>) object;
83      return that.isEmpty();
84    }
85    return false;
86  }
87
88  @Override public int hashCode() {
89    return 0;
90  }
91
92  @Override public String toString() {
93    return "[]";
94  }
95
96  @Override
97  public E first() {
98    throw new NoSuchElementException();
99  }
100
101  @Override
102  public E last() {
103    throw new NoSuchElementException();
104  }
105
106  @Override
107  ImmutableSortedSet<E> headSetImpl(E toElement, boolean inclusive) {
108    return this;
109  }
110
111  @Override
112  ImmutableSortedSet<E> subSetImpl(
113      E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
114    return this;
115  }
116
117  @Override
118  ImmutableSortedSet<E> tailSetImpl(E fromElement, boolean inclusive) {
119    return this;
120  }
121
122  @Override int indexOf(@Nullable Object target) {
123    return -1;
124  }
125
126  @Override
127  ImmutableSortedSet<E> createDescendingSet() {
128    return new EmptyImmutableSortedSet<E>(Ordering.from(comparator).reverse());
129  }
130}
131