The 1-argument split method links both to the 2-argument split method and Pattern. Moreover, the 2-argument split method not only links to Pattern, but to Pattern.compile in particular. On the first line there's a link to the regular expression summary.
On that last page (part of Pattern), it is clearly mentioned that: a) [ is used with ] for a set b) \ is used as escape character, and needs to be duplicated
Now clearly, after seeing just "[" fail, you could have tried it with "\\[" ?