Question

enter code herehello, everyone, can somebody explain what is my problem in this function:

public class Summer{
 public <X,Y> Y[] sum(X[] inArr, Y first, SumFunction<Y,X> f, Y[] outArr){
  for(int i = 0; i < inArr.length; i++){
   outArr[i] = f.op(inArr[i], first); //here I have problem
   first = outArr[i];
  }
  return outArr;
 }
}

I receive an error:

The method op(Y, X) in the type SumFunction<Y,X> is not applicable for the arguments (X, Y)

I need to use this function, how can I do this, thanks for any suggestions

Answer 1

I think you have to call f.op(first, inArray[i]).
The op() method of SumFunction seems to take an Y as the first argument, and an X as the second.