How to fix SonarLint: Refactor this code to use the more specialised Functional Interface 'BinaryOperator<Float>'?

Question

So im learning on how to use Lambda in Java and got the problem, that Sonar Lint is saying i should refactor the code to use the more specialised functional interface.

public float durchschnitt(float zahl1, float zahl2) {
    BiFunction<Float, Float, Float> function = (Float ersteZahl, Float zweiteZahl) -> (ersteZahl + zweiteZahl) / 2;
//  ^
//  Here I get the warning:
//  SonarLint: Refactor this code to use the more specialised Functional Interface 'BinaryOperator<Float>'
    return function.apply(zahl1, zahl2);
  }

All this little program should do is calculate the average of the two floats. The programm's working fine, but I want the warning to be gone. So how can I avoid that waring and fix the code?

Edit: I oc tried finding a solution on google etc., but found none.

Answer 1

The BinaryOperator<T> is in fact a subinterface of BiFunction<T, T, T>, and its documentation states "this is a specialization of BiFunction for the case where the operands and the result are all of the same type", so just replace with:

BinaryOperator<Float> function = (Float ersteZahl, Float zweiteZahl) -> (ersteZahl + zweiteZahl) / 2;

Also no need to declare the Float argument types, it is auto-inferred by the compiler:

BinaryOperator<Float> function = (ersteZahl, zweiteZahl) -> (ersteZahl + zweiteZahl) / 2;