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I have a simple java program that creates an array of random numbers. I am using rJava to call this program and create an R object. I know how to create random numbers in R ... I am trying to reproduce the results of a complicated java program exactly, which requires I use the same random numbers. Here is the java:

import java.util.Random;
public class rJava
{
public static void main(String[] args)
    {
    createRan();
    }

public static double[] createRan()
    {
    int numSims = 100000;
    int m_RandomSeed = 1234567;
    Random m_Rnd  = new Random(m_RandomSeed);
    double[] randoms = new double[100000];

    for(int i=0; i < numSims; i++)
        {
        randoms[i] = m_Rnd.nextDouble();
        }
    return randoms;
    }
}

rJava seems to be working fine for me ... I use the following commands in R and an object called "rans" with 100000 random numbers is created.

library(rJava)
.jinit()
obj <- .jnew("rJava")
rans <- .jcall(obj, "[D", "createRan")

My problem is I went to change the size of the array for testing purposes to something more manageable, like 10 random numbers instead of 100,000. I saved and recompiled rJava.java, and re-ran the R code above. It still created an array of 100,000 numbers. I rebooted my computer and tried again ... still 100,000. I would ultimately like to pass a parameter into the java code to choose the number of random numbers to generate but would like to understand what is going on here first. I know very little about Java, is there some place where the initial state of rJava.java is stored and is being called from? As I said I have recompiled the class file so I would not the "original" would be overwritten.

Thanks

Elbogen
  • 1
  • probably bcz of your for loop. – Ashish Jan 09 '14 at 20:42
  • `javac` creates `.class` files, that's all there is to it. You didn't specify anything about how you compiled the files so there's little more to add. – Marko Topolnik Jan 09 '14 at 20:44
  • I used javac from the command line to compile it ... windows 7 machine if that matters. I've found I can get the R object to reflect the change in the java code if I exit R, delete the class file, and re-compile. – Elbogen Jan 10 '14 at 15:08

0 Answers0