/*
* 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 java.util.Set;
import javax.annotation.Nullable;
/**
* A set which forwards all its method calls to another set. Subclasses should
* override one or more methods to modify the behavior of the backing set as
* desired per the <a
* href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
*
* <p><b>Warning:</b> The methods of {@code ForwardingSet} forward
* <b>indiscriminately</b> to the methods of the delegate. For example,
* overriding {@link #add} alone <b>will not</b> change the behavior of {@link
* #addAll}, which can lead to unexpected behavior. In this case, you should
* override {@code addAll} as well, either providing your own implementation, or
* delegating to the provided {@code standardAddAll} method.
*
* <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 Kevin Bourrillion
* @author Louis Wasserman
* @since 2.0 (imported from Google Collections Library)
*/
@GwtCompatible
public abstract class ForwardingSet<E> extends ForwardingCollection<E>
implements Set<E> {
// TODO(user): identify places where thread safety is actually lost
/** Constructor for use by subclasses. */
protected ForwardingSet() {}
@Override protected abstract Set<E> delegate();
@Override public boolean equals(@Nullable Object object) {
return object == this || delegate().equals(object);
}
@Override public int hashCode() {
return delegate().hashCode();
}
/**
* A sensible definition of {@link #equals} in terms of {@link #size} and
* {@link #containsAll}. If you override either of those methods, you may wish
* to override {@link #equals} to forward to this implementation.
*
* @since 7.0
*/
@Beta protected boolean standardEquals(@Nullable Object object) {
return Sets.equalsImpl(this, object);
}
/**
* A sensible definition of {@link #hashCode} in terms of {@link #iterator}.
* If you override {@link #iterator}, you may wish to override {@link #equals}
* to forward to this implementation.
*
* @since 7.0
*/
@Beta protected int standardHashCode() {
return Sets.hashCodeImpl(this);
}
}
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