/*
* 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 java.util.concurrent.Executor;
/**
* A {@link ListenableFuture} 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 SimpleForwardingListenableFuture}.
*
* @param <V> The result type returned by this Future's {@code get} method
*
* @author Shardul Deo
* @since 4.0
*/
public abstract class ForwardingListenableFuture<V> extends ForwardingFuture<V>
implements ListenableFuture<V> {
/** Constructor for use by subclasses. */
protected ForwardingListenableFuture() {}
@Override
protected abstract ListenableFuture<V> delegate();
@Override
public void addListener(Runnable listener, Executor exec) {
delegate().addListener(listener, exec);
}
/*
* TODO(cpovirk): Use standard Javadoc form for SimpleForwarding* class and
* constructor
*/
/**
* A simplified version of {@link ForwardingListenableFuture} where subclasses
* can pass in an already constructed {@link ListenableFuture}
* as the delegate.
*
* @since 9.0
*/
public abstract static class SimpleForwardingListenableFuture<V>
extends ForwardingListenableFuture<V> {
private final ListenableFuture<V> delegate;
protected SimpleForwardingListenableFuture(ListenableFuture<V> delegate) {
this.delegate = Preconditions.checkNotNull(delegate);
}
@Override
protected final ListenableFuture<V> delegate() {
return delegate;
}
}
}
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