ForwardingCollection.java

/*
 * 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 org.glassfish.jersey.internal.guava;

import java.util.Collection;
import java.util.Iterator;

/**
 * A collection which forwards all its method calls to another collection.
 * Subclasses should override one or more methods to modify the behavior of the
 * backing collection as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 * <p>
 * <p><b>Warning:</b> The methods of {@code ForwardingCollection} 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>
 * <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)
 */
public abstract class ForwardingCollection<E> extends ForwardingObject
        implements Collection<E> {
    // TODO(user): identify places where thread safety is actually lost

    /**
     * Constructor for use by subclasses.
     */
    ForwardingCollection() {
    }

    @Override
    protected abstract Collection<E> delegate();

    @Override
    public Iterator<E> iterator() {
        return delegate().iterator();
    }

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

    @Override
    public boolean removeAll(Collection<?> collection) {
        return delegate().removeAll(collection);
    }

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

    @Override
    public boolean contains(Object object) {
        return delegate().contains(object);
    }

    @Override
    public boolean add(E element) {
        return delegate().add(element);
    }

    @Override
    public boolean remove(Object object) {
        return delegate().remove(object);
    }

    @Override
    public boolean containsAll(Collection<?> collection) {
        return delegate().containsAll(collection);
    }

    @Override
    public boolean addAll(Collection<? extends E> collection) {
        return delegate().addAll(collection);
    }

    @Override
    public boolean retainAll(Collection<?> collection) {
        return delegate().retainAll(collection);
    }

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

    @Override
    public Object[] toArray() {
        return delegate().toArray();
    }

    @Override
    public <T> T[] toArray(T[] array) {
        return delegate().toArray(array);
    }

}