CODEWITHSUNDEEP
javajava-8java-stream
user3525434
user3525434

Reputation: 51

Convert using JAVA 8 Streams

I've tried to change this code to Java 8 streams. My code looks like this:

for(D d : n.getD()) {
    for(M m : d.getT().getM()) {
        if(m.getAC().contains(this)) {
            return d;
        }
    }
}

and I want to convert it to java 8 streams. I've started like this:

  n.getD().stream()
        .map(m -> m.getT().getM())

but then I don't know if I should map again, or use a filter.

Upvotes: 5

Views: 207

Answers (3)

Nick Vanderhoven
Nick Vanderhoven

Reputation: 3093

I don't know about your domain, but to keep it readable I would probably delegate and simplify to something like this:

return n.getD().stream()
               .filter(d -> d.getT().containsAC(this))
               .findFirst()
               .orElse(null);

And then in class T add the delegation method:

public boolean containsAC(AC ac) {
    return m.stream().anyMatch(m -> m.getAC().contains(ac));
}

Upvotes: 1

Anton Balaniuc
Anton Balaniuc

Reputation: 11739

Other possible way is to use anyMatch instead of second filter

return n.getD().stream().filter(
   d -> d.getT().getM().stream().anyMatch(
         m -> m.getAC().contains(this)
   )
).findFirst(); // result will be Optional<D>

Upvotes: 4

nano_nano
nano_nano

Reputation: 12523

one way to handle this:

return n.getD().stream().filter(d -> d.getT().getM().stream().filter(m -> m.getAC().contains(this)).findFirst().isPresent()).findFirst();

in this case a null value is possible.

Upvotes: 2

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