Using string.all with regex

Question

I am trying to check if a string has all the forbidden characters like "/#$%^&" ... i tried to find a solution but couldn't find anything , i just want to check if all characters in the string match regex pattern \w

string.all seems perfect but i cant add regex pattern to it here is what i am trying to do:

 // "abce#ios" must return false because it contains #
 // "abcdefg123" must return true 

fun checkForChars(string :String) :Boolean {
    val pattern = "\\w".toRegex()
   return (string.contains(regex = pattern))
}

thanks in advance

Andrei Tanana · Accepted Answer · 2019-10-03 09:59:15Z

2

You don't need to use regex at all with all:

fun checkForChars(string: String): Boolean = string.all(Char::isLetterOrDigit)

answered Oct 3, 2019 at 9:59

Andrei Tanana

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Daniel · Accepted Answer · 2019-10-03 10:01:00Z

1

You made several mistakes:

\w pattern matches exactly one letter, if you want to match zero or more letters you need to change it to: \w*
Instead of checking whether the string contains the regex, you need to check if it matches the regex.

The final solution is the following:

fun checkForChars(string :String) :Boolean {
    val pattern = "\\w*".toRegex()
   return (string.matches(pattern))
}

answered Oct 3, 2019 at 10:01

Daniel

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3 Comments

nick isra Over a year ago

thanks for your help, that fixed the problem. but i didn't quite understand "\w*" pattern , i searched the web and found this "Matches the preceding element zero or more times." but still didn't understand, if u can explain i would be really grateful

nick isra Over a year ago

"\w" if my string is 1 letter only?

Daniel Over a year ago

\w matches 1 letter exactly, it will match only strings like "a", "b". Since your string can have zero or more letters you use the *. If you want to make sure that you have at least one letter then instead of * you put +

Vitaly Roslov · Accepted Answer · 2019-10-03 10:19:29Z

1

You can use Regex("[^/#$%^&]*").matches(string) to check for the forbidden characters.

You can include any forbidden characters into a [^...]* construction. Though a " character would need to be screened and a \ character would need to be screened twice. Regex("[^\\\\/#$%^&\"]*").

For \\w* regex you can use Regex("\\w*").matches(string)

edited Oct 3, 2019 at 10:19

answered Oct 3, 2019 at 10:04

Vitaly Roslov

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