This is a code for the sentence parsing that does its job properly and FAST.
The main problem is that you really need a database of abbreviations so that phrases such as "Dr. Smith" are not calculated as 2 sentences, which means that the good parser must be language dependent.
I am also providing a list of all English abbreviations with the code.
parser p = new parser();
in.txt is the String for the filename that you wish to parse
out.txt is the String for the filename that you want to have as an output