RegEx performence issue

Question

I have written a regular expression to validate a name. The name can start with alphabetics and can be followed by alphabetics, numbers, a space or a _. The regex that I wrote is:

private static final String REGEX = "([a-zA-Z][a-zA-Z0-9 _]*)*";

If the input is: "kasklfhklasdhklghjsdkgsjkdbgjsbdjKg;" the program gets stuck on matcher.matches().

Pattern pattern = Pattern.compile(REGEX); Matcher matcher = pattern.matcher(input); if (matcher.matches()) { System.out.println("Pattern Matches"); } else { System.out.println("Match Declined"); }

How can I optimize the regex?

To get the best performance ever, you should create your own String validator. Otherwise, let the JVM do the optimizations for you. — Luiggi Mendoza
– Luiggi Mendoza, Commented Dec 8, 2012 at 13:33
String validator? Is it a different strategy then REGEX validation? — Priyank Thakkar
– Priyank Thakkar, Commented Dec 8, 2012 at 13:36
It means parsing the String yourself and check any errors on it, more code but it can be faster than using Regex. Anyway, check the answers of people here. — Luiggi Mendoza
– Luiggi Mendoza, Commented Dec 8, 2012 at 13:37

Amir Pashazadeh · Accepted Answer · 2012-12-08 13:35:25Z

4

Change your regex to:

private static final String REGEX = "[a-zA-Z][a-zA-Z0-9 _]*";

And it will match the String in a click.

answered Dec 8, 2012 at 13:35

Amir Pashazadeh

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