Question

Write a method that, given an array of grades stored as double values, computes and return their mean.
   Write another method that will return an array of the mean grade obtained by an arbitrary number of student.
   This method will take a 2-dimensional array of double values in which each row corresponds to the grade vector
   for a different student. You can compute the mean for each row as you did before...
   Once you are done, be [good] lazy and just reuse your previous method.

   If you are looking for yet another practice opportunity, what about a method that, given the whole matrix,
   would bump up a specific grade of a specific student by a given number of points?
   Signature of this method is not provided below.

*/
public class TinkeringWithArraysLive {
   public static void main(String[] args){
double[] s1 = {90.1, 80.2, 70.3, 30.4, 99.5};
System.out.println("Computing average of grades " + Arrays.toString(s1) + " result is " + mean(s1));

double[][] all = { {50.0, 60.0, 52.0, 58.0, 55.0},
   {60.0, 70.0, 62.0, 68.0, 65.0},
   {70.0, 80.0, 72.0, 78.0, 75.0}
   };
  
System.out.println("Averages for all students are " + Arrays.toString(mean(all)));
   } // end main
  
   public static double mean(double[] grades){
return 0.0;
   }// end method mean for vector of grades
  
   public static double[] mean(double[][] grades){
double[] result = new double[grades.length];
return result;
   }// end method mean for matrix of grades
} // end class

Answer 1

Code:

import java.util.Arrays;

public class TinkeringWithArraysLive {
public static void main(String[] args)
{
   double[] s1 = {90.1, 80.2, 70.3, 30.4, 99.5};
   System.out.println("Computing average of grades " + Arrays.toString(s1) + " result is " + mean(s1));

   double[][] all = { {50.0, 60.0, 52.0, 58.0, 55.0},
   {60.0, 70.0, 62.0, 68.0, 65.0},
   {70.0, 80.0, 72.0, 78.0, 75.0}
   };
  
   System.out.println("Averages for all students are " + Arrays.toString(mean(all)));
} // end main
  
public static double mean(double[] grades)
{
   double total = 0.0;   
   for(int i = 0;i < grades.length;i++)
   {
       total += grades[i];
   }
   return total/grades.length;
}// end method mean for vector of grades
  
public static double[] mean(double[][] grades)
{
   double[] result = new double[grades.length];
   for(int j = 0;j < grades.length;j++)
   {
       double total = 0.0;
       for(int i = 0;i < grades[j].length;i++)
       {
           total += grades[j][i];
       }
       result[j] = total/grades[j].length;
   }
  
  
   return result;
}// end method mean for matrix of grades
} // end class

OUTPUT: