Why Java should be avoided when developing R packages

Here is a good argument.

A java-based R

Renjin is an implementation of R that is written entirely in Java. 

Java vs. COBOL and R vs. SAS

Here is an interesting comparison.

JVM-based R

Renjin, a jvm-based R interpreter. Looks interesting.

Jamsim

Jamsim is a microsimulation took utilizing R and Java. It looks fascinating. Its documentation can improve in the future.