I'm told to convert a lambda with a parameterized constructor to a method reference

Question

Lets say I have a class Gizmo with a constructor that takes a String. Lets say I want to convert a List<String> to a List<Gizmo>.

I might write:

List<String> strings = new ArrayList<>();
List<Gizmo> gizmos = strings
        .stream()
        .map(str -> new Gizmo(str))
        .collect(Collectors.toList());

Now, the problem is that I'm told by IntelliJ that I can replace the lambda with a method reference. Thing is, I'm pretty sure method references can't take parameters.

Answer 1

I think InteliJ means replacing

.map(str -> new Gizmo(str))

with

.map(Gizmo::new)

which is a constructor reference. See detailed explanation here.

Answer 2

Now, the problem is that I'm told by IntelliJ that I can replace the lambda with a method reference.

it simply means you can change this:

.map(str -> new Gizmo(str))

to this:

.map(Gizmo::new)

you can read more about Constructor method reference.