Problem with my Vector

Question

As an assignment for my computer class, I need to create a Student class that lets the user add an undefined number of grades to a Vector called grades. The user must also be able to call method getGPA( ) to return the average of all the grades.
The problem is, I cant seem to change the object returned from grades.get (index i) to a double! I added it as a double but I have no idea how to treat it as a double again. Can someone please explain the obvious error I am making???

Answer 1

(un)helpfully Java 5+ will make your double into a Double Objectfor you automatically.
I'm loving autoboxing:
import java.util.*;
public class AutomatHeaven {
     public static void main(String[] args) {
          List < Integer > list = new ArrayList < Integer > ();
          //add some example data to list:
          for(int i = 0; i <= 10; ++i)
               list.add(i);
          int total = 0;
          for(int n : list)
               total += n;
          System.out.format("total=%d%n", total);
}