Question

I have an ArrayList of Strings, size of which may vary.

List<String> strList1 = new ArrayList<String>();

For each of the Strings, I am calling a method updateDetails(strList1), which processes it and prints an op based on some logic.

I would like to call the above method updateDetails(strList1) for the first string, then for 5 (including first 1) etc in fixed intervals as below

The intervals are 1, 5, 10, 50, 100, 200, 1000

The o/p (if strList1 size is 25) should be something like:

Result for first 1:
Result for first 5:..
Result for first 10:..
Result for total 25 : 

The o/p (if strList1 size is 9) should be something like:

Result for first 1:..
Result for first 5:..
Result for total 9:..

How to go about it?

Answer 1

You can avoid duplicates with

int len = strList1.size();
NavigableSet<Integer> sizes = new TreeSet<>();
sizes.addAll(Arrays.asList(1, 5, 10, 50, 100, 200, 1000, len));
for(int size: sizes.lower(len+1)) {
    List<String> list2 = strList1.subList(0, size);
    // process list2
}

---

If duplicates are not a problem.

int len = strList1.size();
for(int size: new int[] { 1, 5, 10, 50, 100, 200, 1000, len }) {
    if(size > len) continue;
    List<String> list2 = strList1.subList(0, size);
    // process list2
}