How to use Java 8 optional API for method calls that return void

Question

I am a newbie to Java 8 APIs. I have this piece of code, which needs to be optimized using Java Optional.

    if (Objects.nonNull(someDao.getById(id))) {
        someDao.delete(id);
    } else {
        throw new RuntimeException();
    }

I tried using Optional.ofNullable to optimize this piece of code.

    Optional.ofNullable(someDao.getById(id))
            .ifPresent(deleteObject)
            .orElseThrow(() -> new RuntimeException("some error message"));

    private Consumer<SomeObject> deleteObject = someObj-> {
          someDao.delete(someObj.getId());
    };

I am getting an error saying "can't invoke orElseThrow on primitive type void"

How can this be optimized to handle both data persistence and exception handling without using if-else blocks using Optional?

Using optional here will be (slightly) less efficient and doesn't improve readability. So I would stick to the original if/else which clearly shows the intention of the code. — assylias
– assylias, Commented May 1, 2017 at 7:49

Sweeper · Accepted Answer · 2017-05-01 07:40:13Z

1

You need to do this in two separate calls:

Optional<SomeType> opt = Optional.ofNullable(someDao.getById(id));
opt.ifPresent(deleteObject);
opt.orElseThrow(() -> new RuntimeException("some error message"));

answered May 1, 2017 at 7:40

Sweeper

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Comments

Robin Topper · Accepted Answer · 2017-05-01 07:56:43Z

0

I think the if-statement you have is clear and don't see why you'd want to turn it in an Optional chain.

That being said, I also didn't manage to get it all done in one chain:

SomeObject someObj = Optional.ofNullable(someDao.getById(id))
.orElseThrow(() -> new RuntimeException("some error message"));
someDao.delete(someObj.getId());

.orElseThrow returns the value contained in the Optional if it is not null. So you can store it in a SomeObject and then delete it.

edited May 1, 2017 at 7:56

answered May 1, 2017 at 7:48

Robin Topper

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