java - Check non-numeric characters in string

Question

I want to check whether the String contains only numeric characters or it contains alpha-numeric characters too.

I have to implement this check in database transaction where about a hundred-thousand records are going to be fetched and passed through this check, so I need optimized performance answer.

Currently, I have implemented this through a try-catch block: I parsed the string in Integer in try block and checked for the NumberFormatException in the catch block. Please suggest if I'm wrong.

Answer 1

You can check this with a regex.

Suppose that (numeric values only):

String a = "493284835";
a.matches("^[0-9]+$"); // returns true

Suppose that (alphanumeric values only):

String a = "dfdf4932fef84835fea";
a.matches("^([A-Za-z]|[0-9])+$"); // returns true

As Pangea said in the comments area :

If the performance are critical, it's preferrable to compile the regex. See below for an example :

String a = "dfdf4932fef84835fea";
Pattern pattern = Pattern.compile("^([A-Za-z]|[0-9])+$");
Matcher matcher = pattern.matcher(a);

if (matcher.find()) {
    // it's ok
}