1/*
2 * Copyright (C) 2012 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.cache;
18
19import com.google.common.annotations.GwtCompatible;
20import com.google.common.base.Supplier;
21
22import java.util.concurrent.atomic.AtomicLong;
23
24/**
25 * Source of {@link LongAddable} objects that deals with GWT, Unsafe, and all
26 * that.
27 *
28 * @author Louis Wasserman
29 */
30@GwtCompatible(emulated = true)
31final class LongAddables {
32  private static final Supplier<LongAddable> SUPPLIER;
33
34  static {
35    Supplier<LongAddable> supplier;
36    try {
37      new LongAdder();
38      supplier = new Supplier<LongAddable>() {
39        @Override
40        public LongAddable get() {
41          return new LongAdder();
42        }
43      };
44    } catch (Throwable t) { // we really want to catch *everything*
45      supplier = new Supplier<LongAddable>() {
46        @Override
47        public LongAddable get() {
48          return new PureJavaLongAddable();
49        }
50      };
51    }
52    SUPPLIER = supplier;
53  }
54
55  public static LongAddable create() {
56    return SUPPLIER.get();
57  }
58
59  private static final class PureJavaLongAddable extends AtomicLong implements LongAddable {
60    @Override
61    public void increment() {
62      getAndIncrement();
63    }
64
65    @Override
66    public void add(long x) {
67      getAndAdd(x);
68    }
69
70    @Override
71    public long sum() {
72      return get();
73    }
74  }
75}
76