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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.annotations.GwtCompatible;
import com.google.common.base.Preconditions;
import java.util.concurrent.Executor;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* 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 decorator pattern.
*
* Most subclasses can just use {@link SimpleForwardingListenableFuture}.
*
* @author Shardul Deo
* @since 4.0
*/
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class ForwardingListenableFuture
extends ForwardingFuture implements ListenableFuture {
/** Constructor for use by subclasses. */
protected ForwardingListenableFuture() {}
@Override
protected abstract ListenableFuture 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
extends ForwardingListenableFuture {
private final ListenableFuture delegate;
protected SimpleForwardingListenableFuture(ListenableFuture delegate) {
this.delegate = Preconditions.checkNotNull(delegate);
}
@Override
protected final ListenableFuture delegate() {
return delegate;
}
}
}