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Google Collections Library is a suite of new collections and collection-related goodness for Java 5.0

There is a newer version: 1.0

/*
 * Copyright (C) 2008 Google Inc.
 *
 * 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 java.util.Map;

import javax.annotation.Nullable;

/**
 * An empty immutable map.
 * 
 * @author Jesse Wilson
 * @author Kevin Bourrillion
 */
@GwtCompatible(serializable = true)
final class EmptyImmutableMap extends ImmutableMap {
  static final EmptyImmutableMap INSTANCE = new EmptyImmutableMap();

  private EmptyImmutableMap() {}

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

  public int size() {
    return 0;
  }

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

  @Override public boolean containsKey(Object key) {
    return false;
  }

  @Override public boolean containsValue(Object value) {
    return false;
  }

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

  @Override public ImmutableSet