The limit is indeed 2000 but not only for the number
of
lines but for the number of characters in a line
(diffFile)
or a String (diffString).
The code is the following in src/JLibDiff/diff.java :
char input_buffer[] = new char[2000];
input_string.getChars(0, input_string.length(),
input_buffer, 0);
If you put Integer.SIZE in char input_buffer[] = new char[---here---]; it should fix the problem. Unless the lines or characters excedes 2,147,483,647