How to Check that String is alphanumeric in Java

Question

I am trying to check the entered String is alphanumeric or not.I tried some regular expressions i.e.,

 ^[a-zA-Z0-9]+$
 ^[A-Za-z0-9]*$
 ^[\pL\pN]+$

But all these will work if the String contains only numeric or contains only alphabets or alphanumeric. But I need to check the String should be AlphaNumeric and Starts with a digit only. Please help me out.

You can do a try-catch and parse your value to an int or double. If it fails and throws an exception you know it's not a numeric value. — timr
– timr, Commented May 30, 2014 at 12:07
It appears you want to add the requirement that it start with a digit. So I would add a digit to the start of your regex. What did you try to meet this requirement and what problem are you having? — Peter Lawrey
– Peter Lawrey, Commented May 30, 2014 at 12:07
Your question is unclear. You should post some examples of input and expected results with explanation why such results are expected (why they are correct/incorrect)? — Pshemo
– Pshemo, Commented May 30, 2014 at 12:15
Note: AlphaNumeric usually means containing any combination of letters or digits and can be only letters or digits. — Peter Lawrey
– Peter Lawrey, Commented May 30, 2014 at 12:19
IMO an upvote isn't warranted on a regex question like this since (a) exact examples are easily searchable, and (b) the OP clearly hasn't tried very hard to find an answer. While a downvote might be too much, there is little redeeming value given the ambiguous wording and lack of followup. — Dave Newton
– Dave Newton, Commented May 30, 2014 at 12:24

TheLostMind · Accepted Answer · 2014-05-30 12:16:35Z

1

string.matches("[0-9]+[a-zA-Z]+[a-zA-Z0-9]*$"); 
// ensures you have atleast 1 number, 1 alphabet and starts with a number/digit

edited May 30, 2014 at 12:16

answered May 30, 2014 at 12:09

TheLostMind

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7 Comments

Gundamaiah Over a year ago

This one works fine.I need to take the String with , as separator like this '2012IND00013,2012IND0014'.Then how to change this reg exp.Please suggest.

Dave Newton Over a year ago

@Ganesh Split on commas and test each one, particularly if there are an arbitrary number of CSVs. And take some time to learn regexes, espeically when they're this simple.

TheLostMind Over a year ago

@Ganesh - I would take dave's advice :)

Gundamaiah Over a year ago

@DaveNewton Need to check without splitting the String

Dave Newton Over a year ago

@Ganesh ... So use the same expression twice, with a comma in the middle, and watch out for greediness. But a requirement to check without splitting doesn't seem reasonable. Also, not updating the question to be clearer is irresponsible--you were asked to do so, and you saw the confusion your question caused.

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Tim Pietzcker · Accepted Answer · 2014-05-30 12:08:44Z

0

So you want at least one letter after the first digit. Right?

Then use

^[0-9]+[a-zA-Z][a-zA-Z0-9]*$

answered May 30, 2014 at 12:08

Tim Pietzcker

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5 Comments

Peter Lawrey Over a year ago

Not sure it states a letter must appear after a digit.

Tim Pietzcker Over a year ago

@PeterLawrey: Where else would it appear?

Peter Lawrey Over a year ago

Where does the OP state it has to appear anywhere?

Tim Pietzcker Over a year ago

@PeterLawrey: They're in the first sentence after the code sample

Peter Lawrey Over a year ago

@TimPietzcker that sentence is talking about regex the OP doesn't want. He then says But I need to check

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