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/*
 * Copyright (C) 2012 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 java.util.Comparator;
import java.util.Map;

import javax.annotation.Nullable;

/**
 * An empty immutable sorted map.
 *
 * @author Louis Wasserman
 */
@SuppressWarnings("serial") // uses writeReplace, not default serialization
final class EmptyImmutableSortedMap extends ImmutableSortedMap {
  private final transient ImmutableSortedSet keySet;

  EmptyImmutableSortedMap(Comparator comparator) {
    this.keySet = ImmutableSortedSet.emptySet(comparator);
  }

  EmptyImmutableSortedMap(
      Comparator comparator, ImmutableSortedMap descendingMap) {
    super(descendingMap);
    this.keySet = ImmutableSortedSet.emptySet(comparator);
  }

  @Override
  public V get(@Nullable Object key) {
    return null;
  }

  @Override
  public ImmutableSortedSet keySet() {
    return keySet;
  }

  @Override
  public int size() {
    return 0;
  }

  @Override
  public boolean isEmpty() {
    return true;
  }

  @Override
  public ImmutableCollection values() {
    return ImmutableList.of();
  }

  @Override
  public int hashCode() {
    return 0;
  }

  @Override
  public boolean equals(@Nullable Object object) {
    if (object instanceof Map) {
      Map map = (Map) object;
      return map.isEmpty();
    }
    return false;
  }

  @Override
  public String toString() {
    return "{}";
  }

  @Override
  boolean isPartialView() {
    return false;
  }

  @Override
  public ImmutableSet> entrySet() {
    return ImmutableSet.of();
  }

  @Override
  ImmutableSet> createEntrySet() {
    throw new AssertionError("should never be called");
  }

  @Override
  public ImmutableSortedMap headMap(K toKey, boolean inclusive) {
    checkNotNull(toKey);
    return this;
  }

  @Override
  public ImmutableSortedMap tailMap(K fromKey, boolean inclusive) {
    checkNotNull(fromKey);
    return this;
  }

  @Override
  ImmutableSortedMap createDescendingMap() {
    return new EmptyImmutableSortedMap(Ordering.from(comparator()).reverse(), this);
  }
}