How to override kotlin StateFlow fields in Java?

[prime sapphire]

I have an interface class written in kotlin that is also implemented in a java class. one of the fields on the interface is a StateFlow. Now to override this field in kotlin classes is straight forward but what is the proper way to override this in java class ?
Here is the kotlin code:

interface myInterface {
val myvar : StateFlow<TargetClass>
class TargetClass( val name:String? = null)
}

To implement this interface in Java I tried to create a private setter and public getter like

private _myvar = new MutableStateFlow<>(new TargetClass(null))

@Override
public StateFlow<TargetClass> getMyVar() {return _myvar}

but this doesnt compile. What is the correct (and preffered / best) approch to handle this ?

[whole wasp]

<@&1008423204219531294> please have a look, thanks.

[mental axle]

what is the compilation error?

@prime sapphire

[prime sapphire]

@mental axle Im getting MutableStateFlow is an abstract class and can not be instantiated im importing kotlinx.coroutines.flow.MutableStateFlow & kotlinx.coroutines.flow.StateFlow

[onyx cove]

show your actual code. private _myvar = ...; is not proper Java

and thats not a setter, its a variable. setters are methods

[calm jacinth]

well its kotlin

[onyx cove]

they said that was their Java attempt

[calm jacinth]

ah yeah I see

mb

[onyx cove]

Kotlin doesnt use new too. its like a hybrid

no worries

[mental axle]

well, that's not an interface issue, is it?

your class is abstract

[mental axle]

it's a Java implementation of a Kotlin interface

[onyx cove]

yeah, but the variable doesnt have a return type, and its not a setter

they should upload their actual code so we can make sure its not a typo

[mental axle]

anyway

this is not an interface implementation problem, that is set up correctly in fact

it is the attempt to create an instance of MutableStateFlow, which is an interface

you can't do that neither in Kotlin nor in Java

I haven't delved into coroutines and not sure if you're even supposed to use any of that stuff manually, I thought all that is simply the scaffolding used under the hood to make coroutines work

[onyx cove]

im not familiar with MutableStateFlow, its just OP's idea of a "setter" doesnt add up, and they are showing foo-bar like code that doesnt compile

although the docs for MutableStateFlow do state

An instance of MutableStateFlow with the given initial value can be created using MutableStateFlow(value) constructor function.

as well as mentioning that the type is not safe for inheritance

im not familiar with the type, was just trying to get some clarity on their actual code (the attempt they showed)

and i do see examples online of people creating instances of MutableStateFlow

seems strange, but seems possible

[prime sapphire]

sorry for lack of clarity :
this is the code for java.
private final MutableStateFlow<TargetClass> myState = new MutableStateFlow<>(new TargetClass.Initializing(null))

@NotNull
@Override
public StateFlow<TargetClass> getMyState() {
    return myState;
}

in kotlin it is straight forward. i'm confused on how this should be handled in the Java class

[onyx cove]

you need to define a method for the setter

StateFlow<TargetClass> getMyState() {...}

void setMyState(StateFlow<TargetClass> flow) {...}```

setMyState would be the setter. its a method

[mental axle]

the lack of braces in the first post got me confused, there was no indication that you are trying to create an anonymous class

[prime sapphire]

I see. i indeed didnt have a setter method thank you! but how should the value be initalized ? private MutableStateFlow<TargetClass> myState = new MutableStateFlow<>(new TargetClass.Initializing(null)); seems to be wrong as i still get "Mutable StateFlow is abstract and can not be instantiated"

[onyx cove]

you wouldnt initialize the value right away. you would use the setter

[prime sapphire]

@onyx cove should i be using the setter to also set the initial value to fix the error? newbie sorry for the dumb question

[mental axle]

the error is a compile error

you have not defined all the abstract members in a concrete class

whether you should use the setter is a different question, it pertains to application logic

[prime sapphire]

so how do i initialize / assign an initial value for this field ?

[mental axle]

the error is not related to the order of initialization

can be constructor, can be setter

[prime sapphire]

Yes but how should the intialization be handled ? calling the setter from constructor will also cause compilation error because myState has not been intialized and to initalize within constructor, my current approch new StateFlow<>(new TargetClass.Initializing(null)) causes error "StateFlow is an abstract class error"

[onyx cove]

show the exact code you are trying to translate to Java

you've posted so many typos, it's hard to trust the code you are showing

so write the code, compile it, make sure it works, then post using a code block

```lang
code here
```

lang being either Kotlin or Java

or just upload the files directly, so the TJ Bot uploads it to Gist

the less mistakes on your side, the easier it'll be to help on our side

from there, we can more easily help with the translation

[mental axle]

You can initialize within constructor and have the setter, those are not mutually exclusive