Splitting List into sublists along elements

Question

I have this list (List):

[\"a\", \"b\", null, \"c\", null, \"d\", \"e\"]

And I\'d like something like this:

Answer 1

With String one can do:

String s = ....;
String[] parts = s.split("sth");

If all sequential collections (as the String is a sequence of chars) had this abstraction this could be doable for them too:

List l = ...
List> parts = l.split(condition) (possibly with several overloaded variants)

If we restrict the original problem to List of Strings (and imposing some restrictions on it's elements contents) we could hack it like this:

String als = Arrays.toString(new String[]{"a", "b", null, "c", null, "d", "e"});
String[] sa = als.substring(1, als.length() - 1).split("null, ");
List> res = Stream.of(sa).map(s -> Arrays.asList(s.split(", "))).collect(Collectors.toList());

(please don't take it seriously though :))

Otherwise, plain old recursion also works:

List> part(List input, List> acc, List cur, int i) {
    if (i == input.size()) return acc;
    if (input.get(i) != null) {
        cur.add(input.get(i));
    } else if (!cur.isEmpty()) {
        acc.add(cur);
        cur = new ArrayList<>();
    }
    return part(input, acc, cur, i + 1);
}

(note in this case null has to be appended to the input list)

part(input, new ArrayList<>(), new ArrayList<>(), 0)