Detect whether an Expression is a simple number

[danielpeintner]

Detect whether an Expression is a simple number

[RobertZenz]

You could always check whether the String only contains digits in your preprocessing logic, something like:

private static final Pattern NUMBERS_ONLY_PATTERN = Pattern.compile("^(+|-)?[0-9]+$");

String expression = "5*9";

if (NUMBERS_ONLY_PATTERN.matcher(expression.trim()).matches()) {
    // Contains only numbers.
} else {
    // Contains also other characters.
}

[RobertZenz]

I don't think EvalEx really has a utility function for that which is exposed/public, and I'm unsure whether it should have it. Yes, it's of course part of the functionality, but defining whether your expression needs parentheses or not, should be part of your logic, in my opinion.

[danielpeintner]

I agree, of course I can write this part of the code myself. I was just seeing the internal method isNumber(...) which could be made public.

Anyhow, thanks for your reply!