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

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

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.