How to use Java 8 streams to find all values preceding a larger value?

Question

Use Case

Through some coding Katas posted at work, I stumbled on this problem that I\'m not sure how to solve.

Using Java 8 Streams, given a

Answer 1

If you're willing to use a third party library and don't need parallelism, then jOOλ offers SQL-style window functions as follows

System.out.println(
Seq.of(10, 1, 15, 30, 2, 6)
   .window()
   .filter(w -> w.lead().isPresent() && w.value() < w.lead().get())
   .map(w -> w.value())
   .toList()
);

Yielding

[1, 15, 2]

The lead() function accesses the next value in traversal order from the window.

Disclaimer: I work for the company behind jOOλ