What does regex pattern "[\\P{L}]+" mean in Java? [duplicate]

Question

Code:

Arrays.asList("AAAA DDDD, DDDD".split("[\\P{L}]+")).forEach(System.out::println);

Output:

AAAA
DDDD
DDDD

Please notice it's P{L} instead of p{L}(which means letters). I googled it but find nothing. So could any one give me some hint about that?

Answer 1

You can find the explanation in Pattern Javadoc:

Unicode scripts, blocks, categories and binary properties are written with the \p and \P constructs as in Perl. \p{prop} matches if the input has the property prop, while \P{prop} does not match if the input has that property.

So it's the opposite of \p.

Answer 2

Simple: it's the opposite of \\p{L}.

Essentially all "non-letters".

I couldn't find an exact reference in the API, but you can infer the suggestion from the behavior or, say, \\s vs \\S (which is documented there).

Edit (credit to Tunaki for having eyes)

This is actually suggested by the following statement in the documentation:

Unicode blocks and categories are written with the \p and \P constructs as in Perl.