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From: Andreas Leitgeb <avl@logic.at>
Newsgroups: comp.lang.java.programmer
Subject: "less for more" - a little story about String.split
Date: Fri, 27 Jul 2018 06:33:17 -0000 (UTC)
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Imagine you have a variable named "text" of type String, and then you
have this line of code:
   String lines[] = text.split( "\n" );

If text originally pointed to an empty string, then you get an array
of length 1, holding an empty string.

If, however, you append a certain char to that string, then you may
end up with a zero-length array returned from split!  Namely, if ...
(***  drum roll ***)
...the char you added matches split's delimiter: text.equals("\n").

The javadoc of String.split gives these clues about array length in
the case of a 0 limit:

We have clue #1a:
" The array returned by this method contains each substring of this
" string that is terminated by another substring that matches the given
" expression *or is terminated by the end of the string*. [my emphasis]
[this essentially describes the effect of split with a negative limit]

We have clue #1b:
" If the expression does not match any part of the input then the
" resulting array has just one element, namely this string.
[This is just a corollary of #1a for the case of no matches.]

and we have clue #2:
" If n is zero then the pattern will be applied as many times as
" possible, the array can have any length,
" *and trailing empty strings will be discarded*. [again my emphasis]

Which overrides #1a but not #1b.

Could anyone explain to me, why emphasiszed part of clue #2 only
applies to a String that contains at least one delimiter?  Why is
clue #2 weaker than clue #1b but stronger than clue #1a ?

Who else ever had a bug from wrongly assuming that split would
always return an array of length at least 1, or maybe the other
way: expecting 0-length arrays for splitting the empty string
with a limit 0?