How to modify collection's elements with a spliterator

After much searching, I just found that the only operation that is supported by Spliterator is to READ elements from a Collection.

Can someone tell me about another operation in CRUD that can be supported by Spliterator. I tried to modify elements in a Collection using a Spliterator but it didn't work:

    Set<Integer> set = new TreeSet<>();
    set.add(2);
    set.add(3);
    set.add(5);
    set.add(6);
    Spliterator<Integer> si = set.spliterator();
    Spliterator<Integer> sa  = si.trySplit();
    while(sa.tryAdvance(e ->  e= ++e));

    System.out.println("original iterator");
    while(si.tryAdvance(e-> e = ++e));
    System.out.println(set.toString());

Spliterator cannot modify an underlying Collection, mainly because Spliterator (unlike Iterator) is not a strictly Collection-bound interface.

The definition of Iterator (from Iterator's JavaDoc):

An iterator over a collection. [...]

Iterators allow the caller to remove elements from the underlying collection during the iteration with well-defined semantics.

The definition of Spliterator (from Spliterator's JavaDoc):

An object for traversing and partitioning elements of a source. The source of elements covered by a Spliterator could be, for example, an array, a Collection, an IO channel, or a generator function.

EDIT: I just read the code you posted. In this code, you try to mutate an immutable Integer instance inside a Spliterator call. In this case, neither Iterator nor Spliterator can work, because the elements are immutable.

Use a Stream (or an IntStream) for this, together with a map() followed by collect().