java 8：LongAdder和LongAccumulator是AtomicLong的首选吗？

发布时间：2020-12-15 04:32:40 所属栏目：Java 来源：网络整理

导读：LongAdder作为AtomicLong的替代品 ExecutorService executor = Executors.newFixedThreadPool(2); IntStream.range(0,1000) .forEach(i - executor.submit(adder::increment)); stop(executor); System.out.println(adder.sumThenReset()); // = 1000 LongAc

LongAdder作为AtomicLong的替代品

ExecutorService executor = Executors.newFixedThreadPool(2);    
IntStream.range(0,1000)
    .forEach(i -> executor.submit(adder::increment));    
stop(executor);    
System.out.println(adder.sumThenReset());   // => 1000

LongAccumulator是LongAdder的更通用版本

LongBinaryOperator op = (x,y) -> 2 * x + y;
LongAccumulator accumulator = new LongAccumulator(op,1L);

ExecutorService executor = Executors.newFixedThreadPool(2);
IntStream.range(0,10)
    .forEach(i -> executor.submit(() -> accumulator.accumulate(i)));
stop(executor);

System.out.println(accumulator.getThenReset());     // => 2539

我有一些疑问.

> LongAdder总是优先于AtomicLong吗？
> LongAccumulator是LongAdder和AtomicLong的首选吗？

解决方法

Javadoc中提到了这些类之间的差异,以及何时使用其中一个类.从 LongAdder开始：

This class is usually preferable to AtomicLong when multiple threads update a common sum that is used for purposes such as collecting statistics,not for fine-grained synchronization control. Under low update contention,the two classes have similar characteristics. But under high contention,expected throughput of this class is significantly higher,at the expense of higher space consumption.

从LongAccumulator开始：

This class is usually preferable to AtomicLong when multiple threads update a common value that is used for purposes such as collecting statistics,at the expense of higher space consumption.

[…]

Class LongAdder provides analogs of the functionality of this class for the common special case of maintaining counts and sums. The call new LongAdder() is equivalent to new LongAccumulator((x,y) -> x + y,0L).

因此,一个使用另一个取决于您的应用程序打算做什么.它并不总是严格优先,只有在预期高并发并且您需要维持一个共同状态时.

（编辑：李大同）

【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容!