| /* |
| * 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.Map; |
| import java.util.Map.Entry; |
| import org.checkerframework.checker.nullness.compatqual.NullableDecl; |
| |
| /** |
| * A map entry which forwards all its method calls to another map entry. Subclasses should override |
| * one or more methods to modify the behavior of the backing map entry as desired per the <a |
| * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. |
| * |
| * <p><b>Warning:</b> The methods of {@code ForwardingMapEntry} forward <i>indiscriminately</i> to |
| * the methods of the delegate. For example, overriding {@link #getValue} alone <i>will not</i> |
| * change the behavior of {@link #equals}, which can lead to unexpected behavior. In this case, you |
| * should override {@code equals} as well, either providing your own implementation, or delegating |
| * to the provided {@code standardEquals} method. |
| * |
| * <p>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 the entry of a {@code SortedMap} whose |
| * comparator is not consistent with {@code equals}. |
| * |
| * <p>The {@code standard} methods are not guaranteed to be thread-safe, even when all of the |
| * methods that they depend on are thread-safe. |
| * |
| * @author Mike Bostock |
| * @author Louis Wasserman |
| * @since 2.0 |
| */ |
| @GwtCompatible |
| public abstract class ForwardingMapEntry<K, V> extends ForwardingObject implements Map.Entry<K, V> { |
| // TODO(lowasser): identify places where thread safety is actually lost |
| |
| /** Constructor for use by subclasses. */ |
| protected ForwardingMapEntry() {} |
| |
| @Override |
| protected abstract Entry<K, V> delegate(); |
| |
| @Override |
| public K getKey() { |
| return delegate().getKey(); |
| } |
| |
| @Override |
| public V getValue() { |
| return delegate().getValue(); |
| } |
| |
| @Override |
| public V setValue(V value) { |
| return delegate().setValue(value); |
| } |
| |
| @Override |
| public boolean equals(@NullableDecl Object object) { |
| return delegate().equals(object); |
| } |
| |
| @Override |
| public int hashCode() { |
| return delegate().hashCode(); |
| } |
| |
| /** |
| * A sensible definition of {@link #equals(Object)} in terms of {@link #getKey()} and {@link |
| * #getValue()}. If you override either of these methods, you may wish to override {@link |
| * #equals(Object)} to forward to this implementation. |
| * |
| * @since 7.0 |
| */ |
| protected boolean standardEquals(@NullableDecl Object object) { |
| if (object instanceof Entry) { |
| Entry<?, ?> that = (Entry<?, ?>) object; |
| return Objects.equal(this.getKey(), that.getKey()) |
| && Objects.equal(this.getValue(), that.getValue()); |
| } |
| return false; |
| } |
| |
| /** |
| * A sensible definition of {@link #hashCode()} in terms of {@link #getKey()} and {@link |
| * #getValue()}. If you override either of these methods, you may wish to override {@link |
| * #hashCode()} to forward to this implementation. |
| * |
| * @since 7.0 |
| */ |
| protected int standardHashCode() { |
| K k = getKey(); |
| V v = getValue(); |
| return ((k == null) ? 0 : k.hashCode()) ^ ((v == null) ? 0 : v.hashCode()); |
| } |
| |
| /** |
| * A sensible definition of {@link #toString} in terms of {@link #getKey} and {@link #getValue}. |
| * If you override either of these methods, you may wish to override {@link #equals} to forward to |
| * this implementation. |
| * |
| * @since 7.0 |
| */ |
| @Beta |
| protected String standardToString() { |
| return getKey() + "=" + getValue(); |
| } |
| } |