It's a "drop-in" replacement for JDK's "Math" as of Java 8 (cf. MATH-1630).
"AccurateMath" contains pure Java, acccurate, implementations of "Math" functions.
But it is no longer required to implement all of them.
Default is to use the CM implementations in order to retain previous behaviour.
When using the JDK implementations, some unit tests fail (on Java 8).
Class "AccurateMath" was moved to "o.a.c.math4.core" package.
[Unit tests for that class were not moved because they depend on "legacy" classes.]