R help - Oct 2013 - How do I use simple calls to java methods?

I need to learn how to set up two methods (java functions) so I can call them
from R.
Currently I just copy and paste R code into the R console. 
A little piece of the R code inside a loop is:
      linTm <- linTimOfCalStg(dta[i,timCol],tlev) 
      calCk <- calStgOfLinTim(linTm,tlev) 
      if(calCk!=dta[i,timCol]) { 
        print(c(i,dta[i,timCol],linTm,calCk),digits=20) 
        stop("incorrect time conversion") 
      } 
The two functions called have these first lines:
linTimOfCalStg <- function(calStg,tlev) and 
calStgOfLinTim <- function(linTm, tlev) 
which in java substitutes are: 
public final static double linTimOfCalqsStg(String calStg,int tlev)  and  
public final static String calqsStgOfLinTim(double linTm,int tlev) 
both in a java class called "CalqsLin.class" compiled from
"CalqsLin.java".
The R code works.
The purpose of all this is to eliminate duplicate subroutines and 
their duplicate checking ln both languages.
There will be several other subroutines that I will also use in both
languages.
I can start by putting everything into a single directory in Windows seven
to learn.
How do I make this substitution?




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I am surprised to not get a reply. 
I suppose this means that extremely few, if any, use rJava.

rJava.pdf says this, but I am too stupid to interpret it:
Description
.jcall calls a Java method with the supplied arguments.
Usage
.jcall(obj, returnSig = "V", method, ..., evalArray = TRUE,
evalString = TRUE, check = TRUE, interface = "RcallMethod",
simplify = FALSE, use.true.class = FALSE)

Perhaps it means that to replace:
      calCk <- calStgOfLinTim(linTm,tlev) 
and use something like:
      calCk <- .jcall(CalqsLin.class,returnSig = "S",
      calStgOfLinTim(linTm,tlev),evalArray=FALSE, 
      evalString = TRUE, check = TRUE, interface = "RcallMethod",
      simplify = FALSE, use.true.class = TRUE)

I suppose there are other setup things to do, 
like start the JVM (java Virtual machine)
and I don't know what obj means.

Anyway, if I am able to do these simple java method calls, 
it will be a big plus to our data analysis lab to use R conveniently.

Please help




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Thanks so much for the reply.
I did the search for "rJava examples" and found the Scott 
Hoover instructions which seemed like exactly what I needed.
I compiled the java code and copied myExchange.java and 
myExchange.class to the directory where I started R where 
I did and the calls suggested inside worked.
But there are no parameters passed in the examples.
I need to do something like this:
dateStg <- "201310221439591234"
dateStg
doubleLin <- .jcall(CalqsLin, "D",
"linTimOfCalqsStgIsLev",dateStg,-4)
or
doubleLin <- .jcall(CalqsLin, "D",
"linTimOfCalqsStgIsLev","201310221439591234",-4)
where the latter two parameters are passed to linTimOfCalqsStgIsLev.
Neither way works and I cannot understand the .jcall() instructions in
rJava.pdf well enough.
I'll keep trying, but would like help.




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