Android : read text file into vector string android/java

I've read about one trillion answers to this question that don't involve using a vector of strings.

private Vector<String> getLetters(String chapter, int t) throws IOException {
        InputStream is = getResources().openRawResource(com.example.android.myprojecte.R.raw.aa);
        Vector<String> letters = null;  
        InputStreamReader isReaded = new InputStreamReader(is);


        BufferedReader reader = new BufferedReader(isReaded);
        String line = null;

        while ((line = reader.readLine()) != null) {
            letters.add(line);
         }

        return letters;
 }

Basically, I just need to read a text file into a vector string, but my emulator keeps crashing. It could be something with my fragments, but the error code is signifying it's an I/O problem? So is this wrong above please and thank you