A better example of what I'm thinking (assuming these interfaces are in java.lang to allow for safe operator overloading):

    interface Summable {
        static This sum(This v0, This v1); 
    }

    interface Subtractable {
        static This difference(This v0, This v1); 
    }

    interface Divisible {
        static This quotient(This v0, This v1); 
    }

    interface Mulitiplicable {
        static This product(This v0, This v1); 
    }

    interface Number extends Summable, Subtractable, Divisible, Multiplicable;

    void <N extends Number> doThings(N v0, N v1){
        N sum = v0 + v1;
    }