Coverage Summary for Class: CollectionFuture (com.google.common.util.concurrent)

1 /*
2  * Copyright (C) 2006 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 static com.google.common.collect.Lists.newArrayListWithCapacity;
18 import static java.util.Collections.unmodifiableList;
19 
20 import com.google.common.annotations.GwtCompatible;
21 import com.google.common.collect.ImmutableCollection;
22 import com.google.common.collect.Lists;
23 import java.util.Collections;
24 import java.util.List;
25 import javax.annotation.CheckForNull;
26 import org.checkerframework.checker.nullness.qual.Nullable;
27 
28 /** Aggregate future that collects (stores) results of each future. */
29 @GwtCompatible(emulated = true)
30 @ElementTypesAreNonnullByDefault
31 abstract class CollectionFuture<V extends @Nullable Object, C extends @Nullable Object>
32     extends AggregateFuture<V, C> {
33   /*
34    * We access this field racily but safely. For discussion of a similar situation, see the comments
35    * on the fields of TimeoutFuture. This field is slightly different than the fields discussed
36    * there: cancel() never reads this field, only writes to it. That makes the race here completely
37    * harmless, rather than just 99.99% harmless.
38    */
39   @CheckForNull private List<@Nullable Present<V>> values;
40 
41   CollectionFuture(
42       ImmutableCollection<? extends ListenableFuture<? extends V>> futures,
43       boolean allMustSucceed) {
44     super(futures, allMustSucceed, true);
45 
46     List<@Nullable Present<V>> values =
47         futures.isEmpty()
48             ? Collections.<@Nullable Present<V>>emptyList()
49             : Lists.<@Nullable Present<V>>newArrayListWithCapacity(futures.size());
50 
51     // Populate the results list with null initially.
52     for (int i = 0; i < futures.size(); ++i) {
53       values.add(null);
54     }
55 
56     this.values = values;
57   }
58 
59   @Override
60   final void collectOneValue(int index, @ParametricNullness V returnValue) {
61     List<@Nullable Present<V>> localValues = values;
62     if (localValues != null) {
63       localValues.set(index, new Present<>(returnValue));
64     }
65   }
66 
67   @Override
68   final void handleAllCompleted() {
69     List<@Nullable Present<V>> localValues = values;
70     if (localValues != null) {
71       set(combine(localValues));
72     }
73   }
74 
75   @Override
76   void releaseResources(ReleaseResourcesReason reason) {
77     super.releaseResources(reason);
78     this.values = null;
79   }
80 
81   abstract C combine(List<@Nullable Present<V>> values);
82 
83   /** Used for {@link Futures#allAsList} and {@link Futures#successfulAsList}. */
84   static final class ListFuture<V extends @Nullable Object>
85       extends CollectionFuture<V, List<@Nullable V>> {
86     ListFuture(
87         ImmutableCollection<? extends ListenableFuture<? extends V>> futures,
88         boolean allMustSucceed) {
89       super(futures, allMustSucceed);
90       init();
91     }
92 
93     @Override
94     public List<@Nullable V> combine(List<@Nullable Present<V>> values) {
95       List<@Nullable V> result = newArrayListWithCapacity(values.size());
96       for (Present<V> element : values) {
97         result.add(element != null ? element.value : null);
98       }
99       return unmodifiableList(result);
100     }
101   }
102 
103   /** The result of a successful {@code Future}. */
104   private static final class Present<V extends @Nullable Object> {
105     V value;
106 
107     Present(V value) {
108       this.value = value;
109     }
110   }
111 }