Java Generics and adding numbers together

Question

I would like to generically add numbers in java. I\'m running into difficulty because the Numbers class doesn\'t really support what I want to do. What I\'ve tried so far

Answer 1

since the introduction of Java 8 streams and lambda you can have a shorter solution

public interface Adder {

    static  E sumValues(Collection objectsToSum, BinaryOperator sumOp) {
        return objectsToSum.stream().reduce(sumOp).orElse(null);
    }
}

and use it as follows

int sum = Adder.sumValues(List.of(4, 5, 6, 7), Integer::sum);

Note, that Stream::reduce with just accumulator returns Optional that's why I used orElse(null), but I would recommend to send also zero value as parameter to Adder::sumValue