Interpret user input as code

I am writing a collection of mathematical analysis programs and would like to allow the user to input a valid Java math expression which could then be interpreted by the program as new code. I realize that this may have security issues but the programs are only for my personal use. A snippet below shows what I'm trying to do. A user input of e.g. "x*x" would result in the output of 25 i.e. 5 squared. In Perl I was able to do this quite easily via eval($input).
import java.util.*; import java.lang.Math.*; public class TestJava { public static void main (String[] args) { double x = 5.0; System.out.print("Enter a valid Java math function: "); Scanner userInput = new Scanner(System.in); String tString = userInput.next(); System.out.println("f(x) = " + tString); /* How to get this next part to work?? */ System.out.println("For x=5, f(x) = " + ????); } }

Welcome to JavaRanch.

That's what the JEP library does. A GPL'd version is available at http://www.singularsys.com/download/jep-2.4.1-ext-1.1.1-gpl.zip, and examples and documentation are at http://www.singularsys.com/jep/

Thanks for the link. I circumvented the problem in C by first taking in the input in Perl (so I guess I didn't really circumvent the problem in C) and writing out a C program via Perl inserting the user input and then compiling/executing via Perl's system(). Pretty clunky - so I'll definitely check out JEP. Thanks again, D.