Java groupingBy: Get two (or more) groups with single Stream

Question

If I have to generate two groups based on two different fields using Stream, this is one approach I can take:

var prop1Group = beans.stream().collect(Collectors.groupingBy(Bean::getProp1));
var prop2Group = beans.stream().collect(Collectors.groupingBy(Bean::getProp2));

But this approach iterates over the list twice. In an imperative way, I can get the same result in single iteration, like this:

var prop1Group = new HashMap<String, Set<Bean>>();
var prop2Group = new HashMap<String, Set<Bean>>();

for (var bean : beans) {
    prop1Group.computeIfAbsent(bean.getProp1(), key -> new HashSet<>()).add(bean);
    prop2Group.computeIfAbsent(bean.getProp2(), key -> new HashSet<>()).add(bean);
}

Is there anyway to do get the same done in declarative way using streams, without iterating twice?

Answer 1

As per the comment from @Holger, I could write it more declaratively with teeing, like this, but this still costs 2N

beans.stream().collect(
                Collectors.teeing(
                        groupingBy(Bean::getProp1),
                        groupingBy(Bean::getProp2),
                        List::of))