package app. exercise. algebra; public interface Fractional { // get numerator long getN(); 1/ get denominator long getD(); // add operand to object void add (Fractional operand); // subtract operand from object void sub (Fractional operand); // multiply object by operand void mul (Fractional operand); // divide object by operand void div (Fractional operand); // new additive inverse object Fractional negation (); // new multiplicative inverse object Fractional reciprocal (); } } protected abstract void setND (long numerator, long denominator)