How can I divide a continuous RXJava stream on the fly based on the elements in the stream?

Győri Sándor :

The simplest example would be a stream of strings like this:

["3", "a", "b", "c", "1", "a", "2", "a", "b"]

The ones that are numbers describe how many more elements should it's group contain.

Very important that the stream is continuous so we cant just wait for the next number to split the stream.

As far as I know there is no built in functionality for this in RXJava2

var flowable = Flowable.concat(Flowable.fromArray("3", "a", "b", "c", "1", "a", "2", "a", "b"), Flowable.never());

flowable/*Something here*/.blockingSubscribe(System.out::println);

And the expected output would be:

[3, a, b, c]
[1, a]
[2, a, b]

Győri Sándor :

I've later found akarnokd's RxJava2Extensions package. Using that, I was able to construct this, which does what I want:

var flowable = Flowable.concat(Flowable.fromArray("3", "a", "b", "c", "1", "a", "2", "a", "b"), Flowable.never());
flowable.compose(FlowableTransformers.bufferUntil(new Predicate<>() {
    private int remaining = 0;
    @Override
    public boolean test(String next) {
        if(next.chars().allMatch(Character::isDigit)) {
            remaining = Integer.parseInt(next);
        }
        return --remaining < 0;
    }
})).blockingSubscribe(System.out::println);