Use of Java 8 Lambdas with Generics

Question

Is it possible to do this using Predicate interface.

I have a client class that utilizes functions provided by a MathUtility class. Whatever the Mathmatical operation it

Answer 1

A much simpler approach I tired is this.

The point to be noted is that the addition logic doesn't happen at the invoking side instead only within the MathUtility. The downside here is that you have to create Addition classes for every Number type you want the + operation.

System.out.println(
                MathUtility.sum(listOfInts, i->i<4, new MathUtility.IntegerAddition()).get()
); 

class MathUtility {

    static class IntegerAddition implements BinaryOperator {

        @Override
        public Integer apply(Integer t, Integer u) {
            return t + u;
        }

    }


    public static  Optional sum(List list, Predicate condition, BinaryOperator operation){
        //ability to add is only here
            return list.parallelStream()
            .filter(condition)
            .map(i -> i)
            .reduce(operation);
    }

}