Can I have recursive function call inside parallel streams in java

Question

I have a function to model my Data. If the parameter "Entity" contains child, it is enclosed in child names. There are two types of child Type-A & Type-B. For Each type the function is called recursively. This recursive function call exits when the child do not have any more child names.

public void modelMyData(Entity entity) {

    if (entity.getChildNames()[0] != null) {
        Arrays.stream(entity.getChildNames())
                .collect(Collectors.toList())
                .parallelStream()
                .forEach(childType -> {

                        entity.getChild(childType).parallelStream()
                                .forEach(child -> {
                                    modelMyData(child);

                                    });
                        ;
                    });
    }

    System.out.println("INSERT " + entity.getChildAttributeValue());

}

The program works fine for me. But the use of parallel stream is said to be bad in java programming.

Visit http://zeroturnaround.com/rebellabs/java-parallel-streams-are-bad-for-your-health/

Should I use streams instead of parallel streams?

make performance test to see if parallelStream will perform better on your machine — Alex Salauyou
– Alex Salauyou, Commented May 12, 2015 at 8:58
I already did that and streams gave me better performance than parallel streams. This confused me. — Akhil K Kamal
– Akhil K Kamal, Commented May 12, 2015 at 9:06
So use plain streams. Parallel streams would be useful if you perform some kind of IO during processing or/and long-running calculations which you'd like to parallelize among cores. — Alex Salauyou
– Alex Salauyou, Commented May 12, 2015 at 9:09
@AkhilKKamal if you have local I/O you may cause too many non-sequential accesses, which bring down performance for both HDDs and SSDs. — Tassos Bassoukos
– Tassos Bassoukos, Commented May 12, 2015 at 11:18

Tassos Bassoukos · Accepted Answer · 2015-05-12 09:02:44Z

1

Are you doing long-running operations in your streams? If yes, use parallelStream, if not, don't. Have you read the article? It refers to thread pool exhaustion during long-running operations. Is this the case for your problem/program?

As an aside, simply do Arrays.asList(entity.getChildNames()).parallelStream()...., no need to copy everything.

answered May 12, 2015 at 9:02

Tassos Bassoukos

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2 Comments

Akhil K Kamal Over a year ago

My uses cases has I/O operations, so it is recommended that I should go for parallel streams.

Tassos Bassoukos Over a year ago

The question you linked to is about arrays of primitives, but that does not apply to your case, as the child names are objects (you test for equality with null)

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