rJava class not found exception

Question

I'm just trying to get a simple example of accessing a custom java class from within R using rJava.

HelloWorld.java

class HelloWorld {
        public static void main(String[] args){
                System.out.println("Hello World!");
        }
}

compiled .java to .class as such:

javac HelloWorld.java

R code (ran from same directory as HelloWorld.java and HelloWorld.class.

library(rJava)
> .jinit()
[1] 0
> .jnew("HelloWorld")
Error in .jnew("HelloWorld") : java.lang.ClassNotFoundException

Thank you for any pointers.

Answer 1

Since you're using a custom class you need to tell rJava where to find these custom classes. One way to do this is to specify the location of your classes when you call jinit.

library(rJava)
# Assuming HelloWorld is in the current working directory
.jinit(".")
.jnew("HelloWorld")

I would recommend reading the help page for .jinit