Regexesedit

Regular expression constants are directly supported. To ensure fast performance, this is the only mechanism for creating patterns. Regular expressions are always constants and compiled efficiently a single time.

Pattern p = /[aeiou]/

A poorly written regular expression can significantly slow performance. If possible, avoid using regular expressions, particularly in frequently run scripts.

Pattern flagsedit

You can define flags on patterns in Painless by adding characters after the trailing / like /foo/i or /foo \w #comment/iUx. Painless exposes all of the flags from Java’s Pattern class using these characters:

Character Java Constant Example

c

CANON_EQ

'å' ==~ /å/c (open in hex editor to see)

i

CASE_INSENSITIVE

'A' ==~ /a/i

l

LITERAL

'[a]' ==~ /[a]/l

m

MULTILINE

'a\nb\nc' =~ /^b$/m

s

DOTALL (aka single line)

'a\nb\nc' =~ /.b./s

U

UNICODE_CHARACTER_CLASS

'Ɛ' ==~ /\\w/U

u

UNICODE_CASE

'Ɛ' ==~ /ɛ/iu

x

COMMENTS (aka extended)

'a' ==~ /a #comment/x