com.google.common.util.concurrent.ForwardingFuture.java Source code

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Here is the source code for com.google.common.util.concurrent.ForwardingFuture.java

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/*
 * Copyright (C) 2009 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.util.concurrent;

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

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

/**
 * 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 <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p>Most subclasses can just use {@link SimpleForwardingFuture}.
 *
 * @author Sven Mawson
 * @since 1.0
 */
public abstract class ForwardingFuture<V> extends ForwardingObject implements Future<V> {
    /** Constructor for use by subclasses. */
    protected ForwardingFuture() {
    }

    @Override
    protected abstract Future<V> 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<V> extends ForwardingFuture<V> {
        private final Future<V> delegate;

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

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