How to split array list into equal parts?

Question

Is there anyway to split ArrayList into different parts without knowing size of it until runtime? I know there is a method called:

list.subList(a,b);
         


        

Answer 1

Java 8 (not that it has advantages):

List list = new ArrayList<>();
Collections.addAll(list,  "a","b","c","b","c","a","c","a","b");

Grouping size:

final int G = 3;
final int NG = (list.size() + G - 1) / G;

In old style:

List> result = new ArrayList(NG);
IntStream.range(0, list.size())
    .forEach(i -> {
        if (i % G == 0) {
            result.add(i/G, new ArrayList<>());
        }
        result.get(i/G).add(list.get(i));
    });

In new style:

List> result = IntStream.range(0, NG)
    .mapToObj(i -> list.subList(3 * i, Math.min(3 * i + 3, list.size())))
    .collect(Collectors.toList());

Thanks to @StuartMarks for the forgotten toList.