R and Java 10 ➜ rJava not able to build

...

rJava is not yet compatible with Java 10

Is the correct answer.  How to work around this is in the current 
manual, specifically R-admin for R 3.5.0 alpha or R-devel.

Java 10 has been out for 8 days, and the rJava maintainer was made aware 
of the issues early this month, several other package maintainers only 
today.  The advice is to stick to an LTS release of Java (currently 8) 
unless you know what you are doing.

And don't post to multiple lists!

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Emeritus Professor of Applied Statistics, University of Oxford