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
21/**
22 * Implementation of {@link ImmutableListMultimap} with no entries.
23 *
24 * @author Mike Ward
25 */
26@GwtCompatible(serializable = true)
27class EmptyImmutableSetMultimap extends ImmutableSetMultimap<Object, Object> {
28  static final EmptyImmutableSetMultimap INSTANCE
29      = new EmptyImmutableSetMultimap();
30
31  private EmptyImmutableSetMultimap() {
32    super(ImmutableMap.<Object, ImmutableSet<Object>>of(), 0, null);
33  }
34
35  private Object readResolve() {
36    return INSTANCE; // preserve singleton property
37  }
38
39  private static final long serialVersionUID = 0;
40}
41