Need help with JAVA

FractionInterface result = null; result = firstOperand.add(nineSixteenths);

the nineSixteenths is this Fraction nineSixteenths = new Fraction(9, 16);

the .add class is this public FractionInterface add(FractionInterface secondFraction) {

//I am given: numerator = 4

denominator = 16

// so here if we do a println(secondFraction); it prints out "9/16"

I am given an int numerator = 4, and int denominator = 16, how do I get the numerator and denominator out of secondFraction so that I can add them? return null; }