Create stream of streams from one long stream

Question

I want to split a single Stream into a Stream of Streams based on the contents of the Streams. The resulting the St

Answer 1

Like @Jaroslaw, I also used Map to hold the different Streams. However, it is doable that the map will hold Streams that are built from the input and are not collected upfront. Using Stream.concat and Stream.of you can add one element to a stream:

    Map> streamMap = new HashMap<>();

    int[] arr = {1,1,1,2,2,2,3,6,7,7,1,1};
    Arrays.stream(arr)
    .filter(this::isOdd)
    .forEach(i -> {
        Stream st = streamMap.get(i);
        if (st == null)  st = Stream.of(i);
        else st = Stream.concat(st, Stream.of(i));
        streamMap.put(i, st);
    });

    streamMap.entrySet().stream().forEach(e -> {
        System.out.print(e.getKey() + "={");
        e.getValue().forEach(System.out::print);
        System.out.println("}");
    });

Output:

1={11111}
3={3}
7={77}