I am trying to extract phrases using rules such as the ones mentioned below on text which has been POS tagged

1) NNP -> NNP (-> indicates followed by) 2) NNP -> CC -> NNP 3) VP -> NP etc..

I have written code in this manner, Can someone tell me how i can do in a better manner.

    List<String> nounPhrases = new ArrayList<String>();
    for (List<HasWord> sentence : documentPreprocessor) {

        //System.out.println(sentence.toString());
        System.out.println(Sentence.listToString(sentence, false));
        List<TaggedWord> tSentence = tagger.tagSentence(sentence);


        String lastTag = null, lastWord = null;
        for (TaggedWord taggedWord : tSentence) {
            if (lastTag != null && taggedWord.tag().equalsIgnoreCase("NNP") && lastTag.equalsIgnoreCase("NNP")) {
                nounPhrases.add(taggedWord.word() + " " + lastWord);
                //System.out.println(taggedWord.word() + " " + lastWord);

            }
            lastTag = taggedWord.tag();
            lastWord = taggedWord.word();
        }

    }

In the above code, i have done only for NNP followed by NNP extraction, how can i generalise it so that i can add other rules too. I know that there are libraries available for doing this , but wanted to do this manually.