so, let me see if I got constructors straight... 1. if you have a single constructor then

()

after the classname is not required... 2. however if you have secondary constructors then it is now required 3. and now you might also want to make that constructor private

no, it’s incorrect

also one case when you need

constructor

keyword for primary, if you want add annotation to primary constructor or add visibility modifier (what you also mentioned in 3)

ok wait

To create a new instance you always need to use

ClassName()

no,

()

in the class declaration i mean - not invoking it -

class Abc: Def()

vs

class Abc(): Def()

it doesn't make a lot of sense to have a secondary constructor but effectively no primary constructor though

Yes, the shorthand for calling super (

Def()

in your first example) only works with primary constructor.

class Abc()

isn’t invoking a constructor, it’s a redundant set of parens since your constructor is noarg

sure it makes sense, I want to prevent incorrect object creation via noargs constructor in my class

class Abc() : Def()

is short for:

class Abc : Def {
    constructor() : super() {
    }
}

thanks for the help

You are correct that omitting

()

in your class declaration and including a

constructor

in the body removes the implicit no-arg constructor that would otherwise be present .