Regex or Exception Handling?

Question

Which one of the following is a better practice to check if a string is float?

try{
 Double.parseDouble(strVal);
}catch(NumberFormatException e){
 //My Logic         


        

Answer 1

Personal opinion - of the code I've seen, I would expect that most developers would tend towards the try - catch blocks. The try catch is in a sense also more readable and makes the assumption that for most cases the string will contain a valid number. But there are a number of things to consider with you examples which may effect which you choose.

1. How often do you expect the string to not contain a valid number.
2. Note that for bulk processing you should create a Pattern object outside of the loop. This will stop the code from having to recompile the pattern every time.
3. As a general rule you should never use expectations as logic flow. Your try - catch indicates logic if it's not a string, where as your regex indicates logic if it is a number. So it wasn't obvious what the context of the code is.
4. If you choose the regex technique, you are still probably going to have to convert at some point, so in effect, it may be a waste of effort.
5. And finally, is the performance requirements of the application important enough to warrant analysis at this level. Again generally speaking I'd recommend keeping things as simple as possible, making it work, then if there are performance problems, use some code analysis tools to find the bottle necks and tune them out.