| /* |
| * 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 com.google.errorprone.annotations.CanIgnoreReturnValue; |
| 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}. |
| * |
| * @author Shardul Deo |
| * @since 4.0 |
| */ |
| @CanIgnoreReturnValue // TODO(cpovirk): Consider being more strict. |
| @GwtCompatible |
| public abstract class ForwardingListenableFuture<V> extends ForwardingFuture<V> |
| implements ListenableFuture<V> { |
| |
| /** Constructor for use by subclasses. */ |
| protected ForwardingListenableFuture() {} |
| |
| @Override |
| protected abstract ListenableFuture<? extends 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; |
| } |
| } |
| } |