1/*
2 * Copyright (C) 2009 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;
20
21import java.io.Serializable;
22import java.util.Collection;
23import java.util.EnumSet;
24
25/**
26 * Implementation of {@link ImmutableSet} backed by a non-empty {@link
27 * java.util.EnumSet}.
28 *
29 * @author Jared Levy
30 */
31@GwtCompatible(serializable = true, emulated = true)
32@SuppressWarnings("serial") // we're overriding default serialization
33final class ImmutableEnumSet<E extends Enum<E>> extends ImmutableSet<E> {
34  static <E extends Enum<E>> ImmutableSet<E> asImmutable(EnumSet<E> set) {
35    switch (set.size()) {
36      case 0:
37        return ImmutableSet.of();
38      case 1:
39        return ImmutableSet.of(Iterables.getOnlyElement(set));
40      default:
41        return new ImmutableEnumSet<E>(set);
42    }
43  }
44
45  /*
46   * Notes on EnumSet and <E extends Enum<E>>:
47   *
48   * This class isn't an arbitrary ForwardingImmutableSet because we need to
49   * know that calling {@code clone()} during deserialization will return an
50   * object that no one else has a reference to, allowing us to guarantee
51   * immutability. Hence, we support only {@link EnumSet}.
52   */
53  private final transient EnumSet<E> delegate;
54
55  private ImmutableEnumSet(EnumSet<E> delegate) {
56    this.delegate = delegate;
57  }
58
59  @Override boolean isPartialView() {
60    return false;
61  }
62
63  @Override public UnmodifiableIterator<E> iterator() {
64    return Iterators.unmodifiableIterator(delegate.iterator());
65  }
66
67  @Override
68  public int size() {
69    return delegate.size();
70  }
71
72  @Override public boolean contains(Object object) {
73    return delegate.contains(object);
74  }
75
76  @Override public boolean containsAll(Collection<?> collection) {
77    return delegate.containsAll(collection);
78  }
79
80  @Override public boolean isEmpty() {
81    return delegate.isEmpty();
82  }
83
84  @Override public boolean equals(Object object) {
85    return object == this || delegate.equals(object);
86  }
87
88  private transient int hashCode;
89
90  @Override public int hashCode() {
91    int result = hashCode;
92    return (result == 0) ? hashCode = delegate.hashCode() : result;
93  }
94
95  @Override public String toString() {
96    return delegate.toString();
97  }
98
99  // All callers of the constructor are restricted to <E extends Enum<E>>.
100  @Override Object writeReplace() {
101    return new EnumSerializedForm<E>(delegate);
102  }
103
104  /*
105   * This class is used to serialize ImmutableEnumSet instances.
106   */
107  private static class EnumSerializedForm<E extends Enum<E>>
108      implements Serializable {
109    final EnumSet<E> delegate;
110    EnumSerializedForm(EnumSet<E> delegate) {
111      this.delegate = delegate;
112    }
113    Object readResolve() {
114      // EJ2 #76: Write readObject() methods defensively.
115      return new ImmutableEnumSet<E>(delegate.clone());
116    }
117    private static final long serialVersionUID = 0;
118  }
119}
120