1 /* 2 * Copyright (C) 2009 Google Inc. 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 17 package com.google.common.collect; 18 19 import 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) 27 class 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); 33 } 34 35 private Object readResolve() { 36 return INSTANCE; // preserve singleton property 37 } 38 39 private static final long serialVersionUID = 0; 40 } 41
