Assign value of Optional to a variable if present

Question

Hi I am using Java Optional. I saw that the Optional has a method ifPresent.

Instead of doing something like:

Optional object = someMeth         


        

Answer 1

Optional l = stream.filter..... // java 8 stream condition

        if(l!=null) {
            ObjectType loc = l.get();
            Map.put(loc, null);
        }

Answer 2

Quite late but I did following:

String myValue = object.map(x->x.getValue()).orElse("");
                           //or null. Whatever you want to return.

Answer 3

You could use #orElse or orElseThrow to improve the readbility of your code.

Optional<MyObject> object = someMethod();
String myValue = object.orElse(new MyObject()).getValue();

---

Optional<MyObject> object = someMethod();
String myValue = object.orElseThrow(RuntimeException::new).getValue();

Answer 4

.findFirst() returns a Optional<MyType>, but if we add .orElse(null) it returns the get of the optional if isPresent(), that is (MyType), or otherwise a NULL

MyType s = newList.stream().filter(d -> d.num == 0).findFirst().orElse(null);

Answer 5

You need to do two things:

1. Turn your Optional<MyObject> into an Optional<String>, which has a value iff the original Optional had a value. You can do this using map: object.map(MyObject::toString) (or whatever other method/function you want to use).
2. Get the String value of of your Optional<String>, or else return a default if the Optional doesn't have a value. For that, you can use orElse

Combining these:

String myValue = object.map(MyObject::toString).orElse(null);