How is LongAccumulator implemented, so that it is more efficient?

Question

I understand that the new Java (8) has introduced new sychronization tools such as LongAccumulator (under the atomic package).

In the documentation it says that the Long

Answer 1

by this

http://codenav.org/code.html?project=/jdk/1.8.0-ea&path=/Source%20Packages/java.util.concurrent.atomic/LongAccumulator.java

it looks like a spin lock.