if stream().filter is empty

Question

I want to know how to execute code from a stream if the filter does not find values and finds it, an example code:

 @Transactional
public void change(ClassName dep){
    // code
    dep.getFoo()
            .stream()
            .filter(f -> f.getName().equals(doo.getName))
            
}

if the filter has a value then:

user.setFoo(f);

if there is no value in the filter then:

Foo foo = new Foo();
foo.setName("Exp");
user.setFoo(foo);

Answer 1

I would suggest creating a constructor for Foo accepting name.

You can then extract the name with default value of Optional:

Foo foo = dep.getFoo()
        .stream()
        .filter(f -> f.getName().equals(doo.getName))
        .findAny().orElse(new Foo("Exp"));
user.setFoo(foo);

As Holger cleverly noticed using orElseGet would avoid executing the Supplier in case the Optional is not empty (beneficial if the computation is complex or side effects occur):

Foo foo = dep.getFoo()
        .stream()
        .filter(f -> f.getName().equals(doo.getName))
        .findAny().orElseGet(() -> new Foo("Exp"));
user.setFoo(foo);

Since java 11 you can use ifPresentOrElse:

dep.getFoo()
        .stream()
        .filter(f -> f.getName().equals(doo.getName))
        .findAny()
        .ifPresentOrElse(user::setFoo, () -> user.setFoo(new Foo("Exp")));

P.S.: If you cannot create the constructor, you can just create the method to provide it and use it in the above snippet:

public static Foo defaultFoo() {
    Foo foo = new Foo();
    foo.setName("Exp");
    return foo;
}