Passing function as argument to a Function, and using it on Generic object

I would like to do something like below.

private <T> void sliceGenericData (List<T> peData, **FunctionType** getterFunctionX) {
    // ... Some Code ...


    <T>.getterFunction()


    // ... Some Code ...

}

A and B class will be my generic type as <T>. Example for a getter function for class A and B.

public class A{
  long x = 5;
  public long getterFunction1(){
     return x;
  }
}

public class B{
  long x = 1;
  public long getterFunction2(){
     return x;
  }
}

I want to pass a getterFunction as argument to my sliceGenericData() and I would like to use it on type <T> (Class A or B). Since those classes have different name of getter functions as getterFunction2, getterFunction1. How can I do it?

Answer

You can pass a function taking the type as param and producing a Long like this:

private <T> void sliceGenericData (List<T> peData, Function<T, Long> fn) 
{ 
  ... 
  // apply your Object
  Long res = fn.apply(myObj);
  ...
}

Invoke the method by providing the appropriate method for the type:

sliceGenericData(myList, A::getterFunction1);