1 /*
2 * Copyright (C) 2009 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14
15 package com.google.common.util.concurrent;
16
17 import com.google.common.annotations.GwtCompatible;
18 import com.google.common.base.Preconditions;
19 import com.google.common.collect.ForwardingObject;
20 import com.google.errorprone.annotations.CanIgnoreReturnValue;
21 import java.util.concurrent.ExecutionException;
22 import java.util.concurrent.Future;
23 import java.util.concurrent.TimeUnit;
24 import java.util.concurrent.TimeoutException;
25 import org.checkerframework.checker.nullness.qual.Nullable;
26
27 /**
28 * A {@link Future} which forwards all its method calls to another future. Subclasses should
29 * override one or more methods to modify the behavior of the backing future as desired per the <a
30 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
31 *
32 * <p>Most subclasses can just use {@link SimpleForwardingFuture}.
33 *
34 * @author Sven Mawson
35 * @since 1.0
36 */
37 @CanIgnoreReturnValue // TODO(cpovirk): Consider being more strict.
38 @GwtCompatible
39 @ElementTypesAreNonnullByDefault
40 public abstract class ForwardingFuture<V extends @Nullable Object> extends ForwardingObject
41 implements Future<V> {
42 /** Constructor for use by subclasses. */
43 protected ForwardingFuture() {}
44
45 @Override
46 protected abstract Future<? extends V> delegate();
47
48 @Override
49 public boolean cancel(boolean mayInterruptIfRunning) {
50 return delegate().cancel(mayInterruptIfRunning);
51 }
52
53 @Override
54 public boolean isCancelled() {
55 return delegate().isCancelled();
56 }
57
58 @Override
59 public boolean isDone() {
60 return delegate().isDone();
61 }
62
63 @Override
64 @ParametricNullness
65 public V get() throws InterruptedException, ExecutionException {
66 return delegate().get();
67 }
68
69 @Override
70 @ParametricNullness
71 public V get(long timeout, TimeUnit unit)
72 throws InterruptedException, ExecutionException, TimeoutException {
73 return delegate().get(timeout, unit);
74 }
75
76 // TODO(cpovirk): Use standard Javadoc form for SimpleForwarding* class and constructor
77 /**
78 * A simplified version of {@link ForwardingFuture} where subclasses can pass in an already
79 * constructed {@link Future} as the delegate.
80 *
81 * @since 9.0
82 */
83 public abstract static class SimpleForwardingFuture<V extends @Nullable Object>
84 extends ForwardingFuture<V> {
85 private final Future<V> delegate;
86
87 protected SimpleForwardingFuture(Future<V> delegate) {
88 this.delegate = Preconditions.checkNotNull(delegate);
89 }
90
91 @Override
92 protected final Future<V> delegate() {
93 return delegate;
94 }
95 }
96 }