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/*
 * Copyright (C) 2007 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 com.google.common.base.Objects;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.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.
 *
 * 

Warning: The methods of {@code ForwardingMap} forward indiscriminately to the * methods of the delegate. For example, overriding {@link #put} alone will not change the * behavior of {@link #putAll}, which can lead to unexpected behavior. In this case, you should * override {@code putAll} as well, either providing your own implementation, or delegating to the * provided {@code standardPutAll} method. * *

{@code default} method warning: This class does not forward calls to {@code * default} methods. Instead, it inherits their default implementations. When those implementations * invoke methods, they invoke methods on the {@code ForwardingMap}. * *

Each of the {@code standard} methods, where appropriate, use {@link Objects#equal} to test * equality for both keys and values. This may not be the desired behavior for map implementations * that use non-standard notions of key equality, such as a {@code SortedMap} whose comparator is * not consistent with {@code equals}. * *

The {@code standard} methods and the collection views they return are not guaranteed to be * thread-safe, even when all of the methods that they depend on are thread-safe. * * @author Kevin Bourrillion * @author Jared Levy * @author Louis Wasserman * @since 2.0 */ @GwtCompatible @ElementTypesAreNonnullByDefault public abstract class ForwardingMap extends ForwardingObject implements Map { // TODO(lowasser): identify places where thread safety is actually lost /** Constructor for use by subclasses. */ protected ForwardingMap() {} @Override protected abstract Map delegate(); @Override public int size() { return delegate().size(); } @Override public boolean isEmpty() { return delegate().isEmpty(); } @CanIgnoreReturnValue @Override @CheckForNull public V remove(@CheckForNull Object key) { return delegate().remove(key); } @Override public void clear() { delegate().clear(); } @Override public boolean containsKey(@CheckForNull Object key) { return delegate().containsKey(key); } @Override public boolean containsValue(@CheckForNull Object value) { return delegate().containsValue(value); } @Override @CheckForNull public V get(@CheckForNull Object key) { return delegate().get(key); } @CanIgnoreReturnValue @Override @CheckForNull public V put(@ParametricNullness K key, @ParametricNullness V value) { return delegate().put(key, value); } @Override public void putAll(Map map) { delegate().putAll(map); } @Override public Set keySet() { return delegate().keySet(); } @Override public Collection values() { return delegate().values(); } @Override public Set> entrySet() { return delegate().entrySet(); } @Override public boolean equals(@CheckForNull Object object) { return object == this || delegate().equals(object); } @Override public int hashCode() { return delegate().hashCode(); } /** * A sensible definition of {@link #putAll(Map)} in terms of {@link #put(Object, Object)}. If you * override {@link #put(Object, Object)}, you may wish to override {@link #putAll(Map)} to forward * to this implementation. * * @since 7.0 */ protected void standardPutAll(Map map) { Maps.putAllImpl(this, map); } /** * A sensible, albeit inefficient, definition of {@link #remove} in terms of the {@code iterator} * method of {@link #entrySet}. If you override {@link #entrySet}, you may wish to override {@link * #remove} to forward to this implementation. * *

Alternately, you may wish to override {@link #remove} with {@code keySet().remove}, assuming * that approach would not lead to an infinite loop. * * @since 7.0 */ @CheckForNull protected V standardRemove(@CheckForNull Object key) { Iterator> entryIterator = entrySet().iterator(); while (entryIterator.hasNext()) { Entry entry = entryIterator.next(); if (Objects.equal(entry.getKey(), key)) { V value = entry.getValue(); entryIterator.remove(); return value; } } return null; } /** * A sensible definition of {@link #clear} in terms of the {@code iterator} method of {@link * #entrySet}. In many cases, you may wish to override {@link #clear} to forward to this * implementation. * * @since 7.0 */ protected void standardClear() { Iterators.clear(entrySet().iterator()); } /** * A sensible implementation of {@link Map#keySet} in terms of the following methods: {@link * ForwardingMap#clear}, {@link ForwardingMap#containsKey}, {@link ForwardingMap#isEmpty}, {@link * ForwardingMap#remove}, {@link ForwardingMap#size}, and the {@link Set#iterator} method of * {@link ForwardingMap#entrySet}. In many cases, you may wish to override {@link * ForwardingMap#keySet} to forward to this implementation or a subclass thereof. * * @since 10.0 */ protected class StandardKeySet extends Maps.KeySet { /** Constructor for use by subclasses. */ public StandardKeySet() { super(ForwardingMap.this); } } /** * A sensible, albeit inefficient, definition of {@link #containsKey} in terms of the {@code * iterator} method of {@link #entrySet}. If you override {@link #entrySet}, you may wish to * override {@link #containsKey} to forward to this implementation. * * @since 7.0 */ protected boolean standardContainsKey(@CheckForNull Object key) { return Maps.containsKeyImpl(this, key); } /** * A sensible implementation of {@link Map#values} in terms of the following methods: {@link * ForwardingMap#clear}, {@link ForwardingMap#containsValue}, {@link ForwardingMap#isEmpty}, * {@link ForwardingMap#size}, and the {@link Set#iterator} method of {@link * ForwardingMap#entrySet}. In many cases, you may wish to override {@link ForwardingMap#values} * to forward to this implementation or a subclass thereof. * * @since 10.0 */ protected class StandardValues extends Maps.Values { /** Constructor for use by subclasses. */ public StandardValues() { super(ForwardingMap.this); } } /** * A sensible definition of {@link #containsValue} in terms of the {@code iterator} method of * {@link #entrySet}. If you override {@link #entrySet}, you may wish to override {@link * #containsValue} to forward to this implementation. * * @since 7.0 */ protected boolean standardContainsValue(@CheckForNull Object value) { return Maps.containsValueImpl(this, value); } /** * A sensible implementation of {@link Map#entrySet} in terms of the following methods: {@link * ForwardingMap#clear}, {@link ForwardingMap#containsKey}, {@link ForwardingMap#get}, {@link * ForwardingMap#isEmpty}, {@link ForwardingMap#remove}, and {@link ForwardingMap#size}. In many * cases, you may wish to override {@link #entrySet} to forward to this implementation or a * subclass thereof. * * @since 10.0 */ protected abstract class StandardEntrySet extends Maps.EntrySet { /** Constructor for use by subclasses. */ protected StandardEntrySet() {} @Override Map map() { return ForwardingMap.this; } } /** * A sensible definition of {@link #isEmpty} in terms of the {@code iterator} method of {@link * #entrySet}. If you override {@link #entrySet}, you may wish to override {@link #isEmpty} to * forward to this implementation. * * @since 7.0 */ protected boolean standardIsEmpty() { return !entrySet().iterator().hasNext(); } /** * A sensible definition of {@link #equals} in terms of the {@code equals} method of {@link * #entrySet}. If you override {@link #entrySet}, you may wish to override {@link #equals} to * forward to this implementation. * * @since 7.0 */ protected boolean standardEquals(@CheckForNull Object object) { return Maps.equalsImpl(this, object); } /** * A sensible definition of {@link #hashCode} in terms of the {@code iterator} method of {@link * #entrySet}. If you override {@link #entrySet}, you may wish to override {@link #hashCode} to * forward to this implementation. * * @since 7.0 */ protected int standardHashCode() { return Sets.hashCodeImpl(entrySet()); } /** * A sensible definition of {@link #toString} in terms of the {@code iterator} method of {@link * #entrySet}. If you override {@link #entrySet}, you may wish to override {@link #toString} to * forward to this implementation. * * @since 7.0 */ protected String standardToString() { return Maps.toStringImpl(this); } }





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