/*
* Copyright (C) 2008 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.collect;
import com.google.common.annotations.
GwtCompatible;
import javax.annotation.
Nullable;
/**
* Bimap with no mappings.
*
* @author Jared Levy
*/
@
GwtCompatible(emulated = true)
@
SuppressWarnings("serial") // uses writeReplace(), not default serialization
final class
EmptyImmutableBiMap extends
ImmutableBiMap<
Object,
Object> {
static final
EmptyImmutableBiMap INSTANCE = new
EmptyImmutableBiMap();
private
EmptyImmutableBiMap() {}
@
Override public
ImmutableBiMap<
Object,
Object>
inverse() {
return this;
}
@
Override
public int
size() {
return 0;
}
@
Override
public boolean
isEmpty() {
return true;
}
@
Override
public
Object get(@
Nullable Object key) {
return null;
}
@
Override
public
ImmutableSet<
Entry<
Object,
Object>>
entrySet() {
return
ImmutableSet.
of();
}
@
Override
ImmutableSet<
Entry<
Object,
Object>>
createEntrySet() {
throw new
AssertionError("should never be called");
}
@
Override
public
ImmutableSetMultimap<
Object,
Object>
asMultimap() {
return
ImmutableSetMultimap.
of();
}
@
Override
public
ImmutableSet<
Object>
keySet() {
return
ImmutableSet.
of();
}
@
Override
boolean
isPartialView() {
return false;
}
Object readResolve() {
return
INSTANCE; // preserve singleton property
}
}