How to get list of Integer from String

ArrayList<Integer> lst = new ArrayList<Integer>();
for (String field : number.split(" +"))
    lst.add(Integer.parseInt(field));

With Java 8+:

List<Integer> lst = 
    Arrays.stream(number.split(" +")).map(Integer::parseInt).collect(Collectors.toList());

You can use a Scanner to read the string one integer at a time.

Scanner scanner = new Scanner(number);
List<Integer> list = new ArrayList<Integer>();
while (scanner.hasNextInt()) {
    list.add(scanner.nextInt());
}