import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Test {

  // this method converts an int into an arraylist of separate digits
  static List<Integer> changeIntegerToList(int n) {
    // make empty list
    List<Integer> list = new ArrayList<>();
    while (n > 0) // while digits left
    {
      int digit = n % 10; // get least significant digit
      list.add(0, digit); // put in list, at start
      n /= 10; // remove digit
    }

    return list;
  }

  public static void main(String[] args) {
    // test data
    List<Integer> nums = Arrays.asList(23252627, 282526, 25, 42, 4);
    // 'result' is a List
    // each element of 'result' is a List - of all digits in element of nums
    List<List<Integer>> result = new ArrayList<>();
    for (Integer n : nums) { // for each number in nums
      List<Integer> temp = changeIntegerToList(n); // convert to list
      result.add(temp); // add it to result
    }
    // check what we've got
    for (List<Integer> row : result) {
      System.out.println(row);
    }

  }

}