how to separate no and text in java

    String input = "C3H20IO";

    List<String> array1 = new ArrayList<String>();
    List<Integer> array2 = new ArrayList<Integer>();

    Pattern pattern = Pattern.compile("([A-Z][a-z]*)([0-9]*)");
    Matcher matcher = pattern.matcher(input);               
    while(matcher.find()){
        array1.add(matcher.group(1));

        String atomAmount = matcher.group(2);
        int atomAmountInt = 1;
        if((atomAmount != null) && (!atomAmount.isEmpty())){
            atomAmountInt = Integer.valueOf(atomAmount);
        }
        array2.add(atomAmountInt);
    }