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/*
 * Copyright (C) 2007 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.Collection;
import java.util.Map;
import java.util.Set;

import javax.annotation.Nullable;

/**
 * A map which forwards all its method calls to another map. Subclasses should
 * override one or more methods to modify the behavior of the backing map as
 * desired per the decorator pattern.
 *
 * @see ForwardingObject
 * @author Kevin Bourrillion
 * @author Jared Levy
 */
@GwtCompatible
public abstract class ForwardingMap extends ForwardingObject
    implements Map {

  @Override protected abstract Map delegate();

  public int size() {
    return delegate().size();
  }

  public boolean isEmpty() {
    return delegate().isEmpty();
  }

  public V remove(Object object) {
    return delegate().remove(object);
  }

  public void clear() {
    delegate().clear();
  }

  public boolean containsKey(Object key) {
    return delegate().containsKey(key);
  }

  public boolean containsValue(Object value) {
    return delegate().containsValue(value);
  }

  public V get(Object key) {
    return delegate().get(key);
  }

  public V put(K key, V value) {
    return delegate().put(key, value);
  }

  public void putAll(Map map) {
    delegate().putAll(map);
  }

  private transient Set keySet;

  public Set keySet() {
    return (keySet == null) ? keySet = createKeySet() : keySet;
  }

  /**
   * Generates a {@link Set} for use by {@link #keySet()}.
   *
   * 

ForwardingMap's implementation of keySet() calls this method to * generate a collection of values, and then reuses that Set * for subsequent invocations. By default, this Set is the * result of invoking keySet() on the delegate. Override this method if you * want to provide another implementation. * * @return A set for use by keySet(). */ protected Set createKeySet() { return delegate().keySet(); } private transient Collection values; public Collection values() { return (values == null) ? values = createValues() : values; } /** * Generates a {@link Collection} for use by {@link #values()}. * *

ForwardingMap's implementation of {@code values()} calls this method to * generate a collection of values, and then reuses that collection * for subsequent invocations. By default, this collection is the * result of invoking values() on the delegate. Override this method if you * want to provide another implementation. * * @return A set for use by values(). */ protected Collection createValues() { return delegate().values(); } private transient Set> entrySet; public Set> entrySet() { return (entrySet == null) ? entrySet = createEntrySet() : entrySet; } /** * Generates a {@link Set} for use by {@link #entrySet()}. * *

ForwardingMap's implementation of entrySet() calls this method to * generate a set of entries, and then reuses that set for subsequent * invocations. By default, this set is the result of invoking * entrySet() on the delegate. Override this method if you want to * provide another implementation. * * @return A set for use by entrySet(). */ protected Set> createEntrySet() { return delegate().entrySet(); } @Override public boolean equals(@Nullable Object object) { return object == this || delegate().equals(object); } @Override public int hashCode() { return delegate().hashCode(); } }





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