Question

So I would like to start out by telling you that I am learning Java on my own and you guys are the nearest thing I have to teachers. So thank you so much for putting up with my simple and obvious question. I am just trying to learn. Once again I am getting an error that for the life of me I cannot figure out.

Here is the error:

Exception in thread "main" java.lang.NullPointerException
at Advisor_score.All_user.Score1(All_user.java:13)
at Advisor_score.All_user.main(All_user.java:28)

Here is my code for the ratings class:

package Advisor_score;
public class Rating {
    double [] Ratings;
    double sum=0;
    double raw_advisor;
    double advisor_score;
public Rating (double [] x){
        Ratings = x;
        }

public double Score(){
for(int i=2;i<Ratings.length;i++){
    sum+=Ratings[i];
}
raw_advisor=((sum-(3*(Ratings.length-2)))/4);
advisor_score= 2.5+(2.5*(1-Math.pow(Math.E, -.5*raw_advisor)));
return advisor_score;
}

Here is my code for the other class:

package Advisor_score;      

public class All_user{
        double [] ADVISOR_SCORE;
        Rating [] All_users;
        double score;
        public All_user(Rating...args){
                All_users=args;
            }

        public double [] Score1(){
            for (int j = 0;j<All_users.length;j++){
                score=All_users[j].Score();
                ADVISOR_SCORE[j]=score;
                }
            return ADVISOR_SCORE;
        }
        public void print(){
            for(int i = 0;i<ADVISOR_SCORE.length;i++){
            System.out.println(ADVISOR_SCORE[i]);
            }
        }
        public static void main(String[] args){ 
            double p1_1[] = {101,1,5,5,5};
            double p2_1[] = {101,1,1,2,3};
            Rating d = new Rating(p1_1);
            Rating e = new Rating(p2_1);
            All_user all=new All_user(d, e);
            all.Score1();
            all.print();
        }

    }

Again, I cannot thank you guys enough at StackOverflow. Your help has been invaluable!!

Answer 1

You have not initialized the ADVISOR_SCORE and All_users arrays, but you do try to assign values and use them. When you declare

double[] ADVISOR_SCORE; // this is null until assigned

At some point, it needs to be assigned

ADVISOR_SCORE = new double[size];