com.google.common.collect.ForwardingMap Maven / Gradle / Ivy
/*
* 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.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Objects;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
/**
* 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
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();
}
@Override
public V remove(Object object) {
return delegate().remove(object);
}
@Override
public void clear() {
delegate().clear();
}
@Override
public boolean containsKey(Object key) {
return delegate().containsKey(key);
}
@Override
public boolean containsValue(Object value) {
return delegate().containsValue(value);
}
@Override
public V get(Object key) {
return delegate().get(key);
}
@Override
public V put(K key, 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(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
*/
@Beta
protected V standardRemove(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
*/
@Beta
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
*/
@Beta
protected boolean standardContainsKey(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
*/
@Beta
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(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
*/
@Beta
protected abstract class StandardEntrySet extends Maps.EntrySet {
/** Constructor for use by subclasses. */
public 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(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);
}
}