EmptyContiguousSet.java revision 1d580d0f6ee4f21eb309ba7b509d2c6d671c4044 
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*/
14package com.google.common.collect;
15
16import com.google.common.annotations.GwtCompatible;
17
18import java.util.NoSuchElementException;
19import java.util.Set;
20
21import javax.annotation.Nullable;
22
23/**
24 * An empty contiguous set.
25 *
26 * @author Gregory Kick
27 */
28@GwtCompatible(emulated = true)
29@SuppressWarnings("unchecked") // allow ungenerified Comparable types
30final class EmptyContiguousSet<C extends Comparable> extends ContiguousSet<C> {
31  EmptyContiguousSet(DiscreteDomain<C> domain) {
32    super(domain);
33  }
34
35  @Override public C first() {
36    throw new NoSuchElementException();
37  }
38
39  @Override public C last() {
40    throw new NoSuchElementException();
41  }
42
43  @Override public int size() {
44    return 0;
45  }
46
47  @Override public ContiguousSet<C> intersection(ContiguousSet<C> other) {
48    return this;
49  }
50
51  @Override public Range<C> range() {
52    throw new NoSuchElementException();
53  }
54
55  @Override public Range<C> range(BoundType lowerBoundType, BoundType upperBoundType) {
56    throw new NoSuchElementException();
57  }
58
59  @Override ContiguousSet<C> headSetImpl(C toElement, boolean inclusive) {
60    return this;
61  }
62
63  @Override ContiguousSet<C> subSetImpl(
64      C fromElement, boolean fromInclusive, C toElement, boolean toInclusive) {
65    return this;
66  }
67
68  @Override ContiguousSet<C> tailSetImpl(C fromElement, boolean fromInclusive) {
69    return this;
70  }
71
72  //Abstract method doesn't exist in GWT emulation
73  /* @Override */ int indexOf(Object target) {
74    return -1;
75  }
76
77  @Override public UnmodifiableIterator<C> iterator() {
78    return Iterators.emptyIterator();
79  }
80
81  @Override boolean isPartialView() {
82    return false;
83  }
84
85  @Override public boolean isEmpty() {
86    return true;
87  }
88
89  @Override public ImmutableList<C> asList() {
90    return ImmutableList.of();
91  }
92
93  @Override public String toString() {
94    return "[]";
95  }
96
97  @Override public boolean equals(@Nullable Object object) {
98    if (object instanceof Set) {
99      Set<?> that = (Set<?>) object;
100      return that.isEmpty();
101    }
102    return false;
103  }
104
105  @Override public int hashCode() {
106    return 0;
107  }
108}
109
110