public List<String> changeChar(String string, int position, Character ch) {
        List<String> mismatches = new ArrayList<String>();
        StringBuilder stringBuilder = new StringBuilder(string);
        switch (ch) {
            case 'T':
                stringBuilder.setCharAt(position, 'A');
                mismatches.add(stringBuilder.toString());
                stringBuilder.setCharAt(position, 'C');
                mismatches.add(stringBuilder.toString());
                stringBuilder.setCharAt(position, 'G');
                mismatches.add(stringBuilder.toString());
                break;
            case 'A':
                stringBuilder.setCharAt(position, 'T');
                mismatches.add(stringBuilder.toString());
                stringBuilder.setCharAt(position, 'C');
                mismatches.add(stringBuilder.toString());
                stringBuilder.setCharAt(position, 'G');
                mismatches.add(stringBuilder.toString());
                break;
            case 'C':
                stringBuilder.setCharAt(position, 'A');
                mismatches.add(stringBuilder.toString());
                stringBuilder.setCharAt(position, 'T');
                mismatches.add(stringBuilder.toString());
                stringBuilder.setCharAt(position, 'G');
                mismatches.add(stringBuilder.toString());
                break;
            case 'G':
                stringBuilder.setCharAt(position, 'A');
                mismatches.add(stringBuilder.toString());
                stringBuilder.setCharAt(position, 'C');
                mismatches.add(stringBuilder.toString());
                stringBuilder.setCharAt(position, 'T');
                mismatches.add(stringBuilder.toString());
                break;
        }
        return mismatches;
    }