When you class mates tell you, that you didn’t call the reduce method, they mean, that you never use the reduce method.
Your add-method should look somewhat like this:
public static String add(int n1, int n2, int d1, int d2) {
int newn = (n1*d2) + (n2*d1);
int newd = d1*d2;
int divisor = reduce(newn, newd);
newn/=divisor;
newd/=divisor;
int integerComponent=0;
while(newn >= newd) {
integerComponent++;
newn-=newd;
}
String answer ="";
if(integerComponent>0) {
answer += integerComponent +"_";
}
if(newn!=0) {
answer += newn+"/"+newd;
}
return answer;
}
and the multiply method should look like this:
public static String multiply(int n1, int n2, int d1, int d2) {
int newn = n1*n2;
int newd = d1*d2;
int divisor = reduce(newn, newd);
newn/=divisor;
newd/=divisor;
int integerComponent=0;
while(newn >= newd) {
integerComponent++;
newn-=newd;
}
String answer ="";
if(integerComponent>0) {
answer += integerComponent +"_";
}
if(newn!=0) {
answer += newn+"/"+newd;
}
return answer;
}
Remember that you also have to change your reduce method, as it always returns 1 right now!
Edit: Added code to print fraction as mixed fraction.
