Regex expression to check for alphanumeric string does not work

Question

I am trying to test if my String contains a character ( a-z) (A-Z) and a number (0-9)

package testing;

import java.io.*;
import java.security.*;
import javax.xml.bind.DatatypeConverter;
import java.lang.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;


public class Testing extends JPanel 
{

    public static void main(String[] args) 
    {
        String foo = "abc1";

        if (foo.matches(".*[0-9].*") && foo.matches(".*[A-Z].*") && foo.matches(".*[a-z].*"))
        {
            //contain letters and numbers only
            System.out.println("Foo");
        }


    }


}

I am expecting Foo to be printed out but there seems to be a problem with my regex expression. Can someone help me out ??

Thanks

your foo doesn't match foo.matches(".*[A-Z].*")

morgano
– morgano

2014-05-07 03:43:51 +00:00
Commented May 7, 2014 at 3:43 — morgano
– morgano, Commented May 7, 2014 at 3:43
Do the characters have to appear before the number?

Jason
– Jason

2014-05-07 03:48:42 +00:00
Commented May 7, 2014 at 3:48 — Jason
– Jason, Commented May 7, 2014 at 3:48

coder hacker · Accepted Answer · 2014-05-07 03:45:31Z

2

change

foo.matches(".*[0-9].*") && foo.matches(".*[A-Z].*") && foo.matches(".*[a-z].*")

to

foo.matches(".*[0-9].*") && (foo.matches(".*[A-Z].*") || foo.matches(".*[a-z].*"))

answered May 7, 2014 at 3:45

coder hacker

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2 Comments

Jason Over a year ago

You don't need the .* before and after the [] since the expression is not being anchored at the start or end of the source string.

Dawood ibn Kareem Over a year ago

@Jason - Yes he does need them. matches matches the entire expression, not a substring.

awksp · Accepted Answer · 2014-05-07 03:43:38Z

1

Your problem is that foo.matches(".*[A-Z].*") will return false, as there are no capital letters in foo = "abc1".

answered May 7, 2014 at 3:43

awksp

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Comments

CoderDre · Accepted Answer · 2014-05-07 04:25:56Z

1

foo.matches(".*([0-9]+).*") && foo.matches(".*([a-zA-Z]+).*")

edited May 7, 2014 at 4:25

answered May 7, 2014 at 3:45

CoderDre

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Comments

Jason · Accepted Answer · 2014-05-07 04:03:00Z

0

The following will identify a match in one regex:

foo.matches(".*([0-9].*[a-zA-Z])|([a-zA-Z].*[0-9]).*")

edited May 7, 2014 at 4:03

answered May 7, 2014 at 3:51

Jason

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5 Comments

Jason Over a year ago

No, it matches strings that have a letter anywhere before a number or a number anywhere before a letter. I didn't use ^ or $ so it is not anchored to the start or end of the source string.

coder hacker Over a year ago

Why .*? (.*) itself means 0 or more, no need of ?

Jason Over a year ago

@TejasPatel ? means reluctant grab. In this case it isn't required.

hwnd Over a year ago

I am unclear for the fact that he just wants to match a-z A-Z 0-9

Jason Over a year ago

@hwnd Read the first line of the question. "I am trying to test if my String contains a character (a-z) (A-Z) and a number (0-9)"

Bhesh Gurung · Accepted Answer · 2014-05-07 15:38:06Z

0

You can use a single expression instead of multiple as follows -

if (foo.matches("(?=.*[a-zA-Z])(?=.*[0-9]).*")) {
    //...

That will make sure that foo contains at least one of the alphabets (lower or capital) and at least of the digits.

edited May 7, 2014 at 15:38

answered May 7, 2014 at 4:05

Bhesh Gurung

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4 Comments

Dawood ibn Kareem Over a year ago

What's the performance of this expression like? I have a suspicion it might run very slowly on large strings.

Bhesh Gurung Over a year ago

How large strings are we talking about?

Dawood ibn Kareem Over a year ago

I don't know. It was just a question. I've seen regular expressions similar to this one running into problems, when the string being matched was only a dozen characters or so. It would be interesting to test this.

Bhesh Gurung Over a year ago

Seems like myregextester.com is a good online tool for the purpose. You can test the pattern ^(?=.*[a-zA-Z])(?=.*[0-9]).*$ there with different inputs of your choice and see the results.

Muthu · Accepted Answer · 2014-05-07 05:17:20Z

-1

Try the following Regex for Alpha Numeric...

foo.matches("\\w.*")

Or

foo.matches("\\w+");

answered May 7, 2014 at 5:17

Muthu

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1 Comment

Dawood ibn Kareem Over a year ago

" ... contains a character AND a number ... "

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