Thread: Maximum common divisor

public class GreatestCommonDivisor {
public static void main(String[] args) {
System.out.println(getGreatestCommonDivisor(20,10) );

}
public static int getGreatestCommonDivisor(int first, int second){
if(first < 10 || second < 10){
return -1;
}
int divisor = 1;
if(first > second){
divisor = first % second;
}
if(second > first){
divisor = second % first;
}


return divisor;
}
}



The exercise in the course i'm studying says as a tip to use a while or for loop, and that is the problem. I've read other threads about greatest common divisors and in their code demonstrations the loops have an array keyword. I don't know about such thing. The professor never teached about arrays or other keywords like that, so I'm lost. You can see there that the if statements where the remainder operators are are wrong, since 20 % 10 is 0 and 0 is not a divisor. Would you please take your time to explain arrays to me, or is it too complicated for them to be explained here?

public class GreatestCommonDivisor {
    public static void main(String[] args) {
        System.out.println(getGreatestCommonDivisor(20,10));
 
    }
    public static int getGreatestCommonDivisor(int first, int second){
        if(first < 10 || second < 10){
            return -1;
        }
        int divisor = 1;
        if(first > second){
            divisor = first % second;
        }
        if(second > first){
            divisor = second % first;
        }
 
 
        return divisor;
    }
}

--- Update ---

What do you mean by writing code before having a working algorithm? I'm sorry, I'm new to this

The exercise says that the numbers should be equal or greater than 10.
And the statement: divisor = first % second; is using an algorithm I read in wikipedia. It is wrong I see.

I'll work on an algorithm now and consult later if I need to. Thank you!