public ArrayList<ArrayList<String>> splitString(String input) {
        sentence = input;
        ArrayList<String> sentenceArray, tokenizedSentence = new ArrayList<>(), charIdentifier = new ArrayList<>();

	// splits sentence into single words at spaces
        // Note: will also bring punctuation with word (if applicable)
        // i.e. "Hi, I'm Akali" will split into "Hi,", "I'm", and "Akali"
        sentenceArray = new ArrayList<>(Arrays.asList(sentence.split("[@ _ \\t\r]")));
        for (int i = 0; i < sentenceArray.size(); i++) {
            for (int r = 0; r < contractions.length; r++) {
                if (sentenceArray.get(i).equalsIgnoreCase(contractions[r][0])) {
                    sentenceArray.set(i, contractions[r][1].split(" ")[0]);
                    sentenceArray.add(i + 1, contractions[r][1].split(" ")[1]);
                }
            }
        }

        for (String s : sentenceArray) {

            if (!(s.equals(""))) {

                // checks last char of s for punctuation
                punctuation = s.substring(s.length() - 1);
                if (punctuation.matches("[, ; : . ? !  ( )  [ ] \" ]")) {
                    s = s.substring(0, s.length() - 1);
                } else {
                    punctuation = "";
                }

            }

            if (s.substring(0, 1).matches("[, ; : ( [ ] ) \"]")) {
                tokenizedSentence.add(s.substring(0, 1));
                charIdentifier.add("Punctuation");
                tokenizedSentence.add(s.substring(1, s.length()));
                charIdentifier.add("Word");
                tokenizedSentence.add(" ");
                charIdentifier.add("space");
                punctuation = "";
                continue;

            }

            tokenizedSentence.add(s);
            charIdentifier.add("Word");

            if (!(punctuation.equals(""))) {

                tokenizedSentence.add(punctuation);
                charIdentifier.add("Punctuation");
            }

            tokenizedSentence.add(" ");
            charIdentifier.add("space");
            punctuation = "";

        }

        return this.passVar(tokenizedSentence, charIdentifier);

    }