Java Stream: how to pass Set to Stream.of() and call method on each elemnt?

Question

i have such old-style code:

            if (setContainer.getSet() == null) {

            return null;

        }

        for (SetElement setElement : setContainer.getSet()){

            if ("SomeString".equals(SetElement.getCode())) {

                return  setElement.getValue();

            }

        }

        return null;

i've tried this but it doesnt check if Set is null:

setContainer.getSet()

                    .stream()

                    .filter(setValue ->  "SomeValue".equals(setElement.getCode()))

                    .map(SetElement::getValue)

                    .findAny()

                    .orElse(null) ;

as i understand, i should use

Stream.of()

but i dont understand how to perform code as above, because it always returns

Optional<Set<SetElement>>

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Answer 1

You can use Optional.ofNullable to achieve this:

return Optional.ofNullable(setContainer.getSet())
    .flatMap(set -> set.stream()
        .filter(e ->  "SomeValue".equals(e.getCode()))
        .map(SetElement::getValue)
        .findAny())
    .orElse(null);

Java Stream: how to pass Set to Stream.of() and call method on each elemnt?

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