rJava is a simple R-to-Java interface. It is comparable to the .C/.Call C interface. rJava provides a low-level bridge between R and Java (via JNI). It allows to create objects, call methods and access fields of Java objects from R. rJava release versions can be obtained from CRAN - usually install.packages("rJava") in R will do the trick. The current development version can be downloaded from the