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Kotlin Regex Pattern

Regex uses several symbolic notation (patterns) in its function. Some commonly uses patterns are given below:

Symbol Description
x|y Matches either x or y
xy Matches x followed by y
[xyz] Matches either x,y,z
[x-z] Matches any character from x to z
[^x-z] '^' as first character negates the pattern. This matches anything outside the range x-z
^xyz Matches expression xyz at beginning of line
xyz$ Matches expression xyz at end of line
. Matches any single character

Regex Meta Symbols

Symbol Description
\d Matches digits ([0-9])
\D Matches non-digits
\w Matches word characters
\W Matches non-word characters
\s Matches whitespaces [\t\r\f\n]
\S Matches non-whitespaces
\b Matches word boundary when outside of a bracket. Matches backslash when placed in a bracket
\B Matches non-word boundary
\A Matches beginning of string
\Z Matches end of String

Regex Quantifiers Patterns

Symbol Description
abcd? Matches 0 or 1 occurrence of expression abcd
abcd* Matches 0 or more occurrences of expression abcd
abcd+ Matches 1 or more occurrences of expression abcd
abcd{x} Matches exact x occurrences of expression abcd
abcd{x,} Matches x or more occurrences of expression abcd
abcd{x,y} Matches x to y occurrences of expression abcd

Regex Sample Patterns

Pattern Description
([^\s]+(?=\.(jpg|gif|png))\.\2) Matches jpg,gif or png images.
([A-Za-z0-9-]+) Matches latter, number and hyphens.
(^[1-9]{1}$|^[1-4]{1}[0-9]{1}$|^100$) Matches any number from 1 to 100 inclusive.
(#?([A-Fa-f0-9]){3}(([A-Fa-f0-9]){3})?) Matches valid hexa decimal color code.
((?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,15}) Matches 8 to 15 character string with at least one upper case, one lower case and one digit.
(\w+@[a-zA-Z_]+?\.[a-zA-Z]{2,6}) Matches email address.
(\<(/?[^\>]+)\>) Matches HTML tags.

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