既然已经意识到Atomic***有这样的业务缺陷，Doug Lea大神又给我们提供了LongAdder，内部的实现有点类似ConcurrentHashMap的分段锁，最好的情况下，每个线程都有独立的计数器，这样可以大量减少并发操作。

下面通过JMH比较一下AtomicLong 和 LongAdder的性能。

@OutputTimeUnit(TimeUnit.MICROSECONDS)
@BenchmarkMode(Mode.Throughput)
public class Main {private static AtomicLong count = new AtomicLong();private static LongAdder longAdder = new LongAdder();public static void main(String[] args) throws Exception {Options options = new OptionsBuilder().include(Main.class.getName()).forks(1).build();new Runner(options).run();}@Benchmark@Threads(10)public void run0(){count.getAndIncrement();}@Benchmark@Threads(10)public void run1(){longAdder.increment();}
}

Benchmark   Mode  Cnt    Score   Error   Units
Main.run0  thrpt    5  154.525 ± 9.767  ops/us
Main.run1  thrpt    5   89.599 ± 7.951  ops/us

Benchmark  Mode  Cnt  Score    Error  Units
Main.run0  avgt    5  0.007 ±  0.001  us/op
Main.run1  avgt    5  0.011 ±  0.001  us/op

Benchmark   Mode  Cnt    Score     Error   Units
Main.run0  thrpt    5   37.780 ±   1.891  ops/us
Main.run1  thrpt    5  464.927 ± 143.207  ops/us

Benchmark  Mode  Cnt  Score   Error  Units
Main.run0  avgt    5  0.290 ± 0.038  us/op
Main.run1  avgt    5  0.021 ± 0.001  us/op

Benchmark   Mode  Cnt    Score    Error   Units
Main.run0  thrpt    5   36.215 ±  2.341  ops/us
Main.run1  thrpt    5  486.630 ± 26.894  ops/us

Benchmark  Mode  Cnt  Score   Error  Units
Main.run0  avgt    5  0.792 ± 0.021  us/op
Main.run1  avgt    5  0.063 ± 0.002  us/op