1 /* 2 * Copyright (C) 2012 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.cache; 16 17 import com.google.common.annotations.GwtCompatible; 18 import com.google.common.base.Supplier; 19 import java.util.concurrent.atomic.AtomicLong; 20 21 /** 22 * Source of {@link LongAddable} objects that deals with GWT, Unsafe, and all that. 23 * 24 * @author Louis Wasserman 25 */ 26 @GwtCompatible(emulated = true) 27 @ElementTypesAreNonnullByDefault 28 final class LongAddables { 29 private static final Supplier<LongAddable> SUPPLIER; 30 31 static { 32 Supplier<LongAddable> supplier; 33 try { 34 // trigger static initialization of the LongAdder class, which may fail 35 LongAdder unused = new LongAdder(); 36 supplier = 37 new Supplier<LongAddable>() { 38 @Override 39 public LongAddable get() { 40 return new LongAdder(); 41 } 42 }; 43 } catch (Throwable t) { // we really want to catch *everything* 44 supplier = 45 new Supplier<LongAddable>() { 46 @Override 47 public LongAddable get() { 48 return new PureJavaLongAddable(); 49 } 50 }; 51 } 52 SUPPLIER = supplier; 53 } 54 create()55 public static LongAddable create() { 56 return SUPPLIER.get(); 57 } 58 59 private static final class PureJavaLongAddable extends AtomicLong implements LongAddable { 60 @Override increment()61 public void increment() { 62 getAndIncrement(); 63 } 64 65 @Override add(long x)66 public void add(long x) { 67 getAndAdd(x); 68 } 69 70 @Override sum()71 public long sum() { 72 return get(); 73 } 74 } 75 } 76