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/*
 * Original Guava code is copyright (C) 2015 The Guava Authors.
 * Modifications from Guava are copyright (C) 2015 DiffPlug.
 *
 * 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.util.concurrent;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import com.google.common.base.Preconditions;
import com.google.common.collect.ForwardingObject;

/**
 * A {@link Future} which forwards all its method calls to another future.
 * Subclasses should override one or more methods to modify the behavior of
 * the backing future as desired per the decorator pattern.
 *
 * Most subclasses can just use {@link SimpleForwardingFuture}.
 * 
 * @author Sven Mawson
 * @since 1.0
 */
public abstract class ForwardingFuture extends ForwardingObject
		implements Future {

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

	@Override
	protected abstract Future delegate();

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

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

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

	@Override
	public V get() throws InterruptedException, ExecutionException {
		return delegate().get();
	}

	@Override
	public V get(long timeout, TimeUnit unit)
			throws InterruptedException, ExecutionException, TimeoutException {
		return delegate().get(timeout, unit);
	}

	/*
	 * TODO(cpovirk): Use standard Javadoc form for SimpleForwarding* class and
	 * constructor
	 */
	/**
	 * A simplified version of {@link ForwardingFuture} where subclasses
	 * can pass in an already constructed {@link Future} as the delegate.
	 * 
	 * @since 9.0
	 */
	public abstract static class SimpleForwardingFuture
			extends ForwardingFuture {
		private final Future delegate;

		protected SimpleForwardingFuture(Future delegate) {
			this.delegate = Preconditions.checkNotNull(delegate);
		}

		@Override
		protected final Future delegate() {
			return delegate;
		}

	}
}