/*
 * 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 static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.j2objc.annotations.Weak;
import java.io.Serializable;
import java.util.Spliterator;
import java.util.function.Consumer;
import org.checkerframework.checker.nullness.qual.Nullable;

keySet() implementation for ImmutableMap.
Author:Jesse Wilson, Kevin Bourrillion
/** * {@code keySet()} implementation for {@link ImmutableMap}. * * @author Jesse Wilson * @author Kevin Bourrillion */
@GwtCompatible(emulated = true) final class ImmutableMapKeySet<K, V> extends IndexedImmutableSet<K> { @Weak private final ImmutableMap<K, V> map; ImmutableMapKeySet(ImmutableMap<K, V> map) { this.map = map; } @Override public int size() { return map.size(); } @Override public UnmodifiableIterator<K> iterator() { return map.keyIterator(); } @Override public Spliterator<K> spliterator() { return map.keySpliterator(); } @Override public boolean contains(@Nullable Object object) { return map.containsKey(object); } @Override K get(int index) { return map.entrySet().asList().get(index).getKey(); } @Override public void forEach(Consumer<? super K> action) { checkNotNull(action); map.forEach((k, v) -> action.accept(k)); } @Override boolean isPartialView() { return true; } @GwtIncompatible // serialization @Override Object writeReplace() { return new KeySetSerializedForm<K>(map); } @GwtIncompatible // serialization private static class KeySetSerializedForm<K> implements Serializable { final ImmutableMap<K, ?> map; KeySetSerializedForm(ImmutableMap<K, ?> map) { this.map = map; } Object readResolve() { return map.keySet(); } private static final long serialVersionUID = 0; } }