RegEx help requested.

Question

Hello, All.
I am new to Java and I am not much familiar with Java regExp package as well. I am looking into it though. I have a specific question related to Reg Exp creation.
We are in need of parsing a string like "XXX > 6 && YYY> 10" [Meaning variable XXX is greater than 6 and variable YYY is greater than 10 ] please note that this string/condition is dynamic and we need to support the normal operators and AND and OR operator for clubbing the condition.
We are just thinking that whether regex will solve our problem? if so how it can be recommended used and what would be the sample of regex grammer?
Thanks a lot in advance for your help.
Best Regards,
Prasanna.

Answer 1

novice_questions wrote:
Thanks for your reply. It may not have brackets in side the expression.
LHS = will contain alphabets/digits and . [xxx.a1]
RHS = [0-9]
Operator can be [>,<]
But this expression can be combined [AND,OR]
like [exp]+[AND,OR][exp] ..some thing like this.
Thanks,
Prasanna.As already mentioned: you can't use regex for this. You either have to write your own parser or, if the expression stay as simple as you posted, use the existing script engine from Java 1.6.
Here's a small demo:
import javax.script.*;
public class Test {
    public static void main(String[] args) throws Exception {
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("js");
        String expression = "a > 2 && b < 2";
        engine.put("a", 3);
        engine.put("b", 1);
        System.out.println(engine.eval(expression));
}