Java Optional Get if Present

Question

I have a java optional object that I only want to get if it's present. The obvious code here is:

JsonGenerator gen;
if(value.isPresent()) {
    gen.writeObject(value.get());
}

But I want to see if I can steamline that to 1 line with the ifPresent method. I don't want it to write at all if it's not present. I tried something like this:

gen.writeObject(value.ifPresent(a -> a));

But that clearly didn't work. Is there any way to do what I want? Everything I've researched online only shows the use of ifPresent with a method call for the predicate.

Edit 1: I tried Tunaki's solution but I am getting the following error:

Error:(25, 46) java: incompatible thrown types java.io.IOException in method reference

Here's my entire block of code:

public class FooSerializer extends JsonSerializer<Foo> {
    @Override
    public void serialize(Foo value,
                          JsonGenerator gen,
                          SerializerProvider serializers) throws IOException {
        value.getFooA().ifPresent(gen::writeObject);
    }
}

I even tried:

public class FooSerializer extends JsonSerializer<Foo> {
    @Override
    public void serialize(Foo value,
                          JsonGenerator gen,
                          SerializerProvider serializers) throws IOException {
        try {
            value.getContactInfo().ifPresent(gen::writeObject);
        } catch(IOException e) {
            throw new UncheckedIOException(e);
        }
    }
}

But it still gives me the error.

Answer 1

You can invoke gen.writeObject as a consumer of your object in ifPresent:

value.ifPresent(gen::writeObject);

This will invoke the method only if the Optional isn't empty.

In your example, the method writeObject throws the checked exception IOException; you will need to catch it and either throw a runtime exception instead (like the new UncheckedIOException, which complicates a little the code) or do something else (like log it):

value.ifPresent(v -> {
    try {
        gen.writeObject(v);
    } catch (IOException e) {
        throw new UncheckedIOException(e);
    }
});