ADDITIONAL SYSTEM INFORMATION :
Microsoft Windows 10 Pro 10.0.19042

A DESCRIPTION OF THE PROBLEM :
Nesting a `flatMap` call inside another `flatMap` produces a complete stream buffering as the one described at https://bugs.java.com/bugdatabase/view_bug.do?bug_id=8075939

The inner Stream seems to be completely evaluated, making it impossible to use Streams comfortably in some lazy-evaluated applications (cartesian product, for instance) that would seem natural given the API.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Execute a `flatMap` operation nested in another `flatMap` operation.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
a
ax
axx
axxx
axxxx
ACTUAL -
OutOfMemoryException as sd::repeat is evaluated from start to finish filling the heap with repetitions of the string "x".

---------- BEGIN SOURCE ----------
    public static void main(String[] args) {
        var max = Integer.MAX_VALUE;
        Stream.of("a", "b", "c")
            .flatMap(s -> Stream.of("x", "y")
                .flatMap(sd -> IntStream.rangeClosed(0, max)
                    .mapToObj(sd::repeat)))
            .map(s -> s + "u")
            .limit(5)
            .forEach(System.out::println);
    }
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
None found using the Streams API.

FREQUENCY : always