Generics and the ArrayList Class - Absolute Java - page 775

Display 14.3 Golf Score Program (part 2 of 3)

21 {
22 System.out.println("Enter a list of nonnegative numbers.");
23 System.out.println(
"Mark the end of the list with a negative number.");
24 Scanner keyboard = new Scanner(System.in);

25 double next;
26 int index = 0;
27 next = keyboard.nextDouble();
28 while (next >= 0)
29 {
30 a.add(next);
31 next = keyboard.nextDouble();
32 }
33 }
34 /**
35 Returns the average of numbers in a.
36 */
37 public static double computeAverage(ArrayList<Double> a)
38 {
39 double total = 0;
40 for (Double element : a)
41 total = total + element;
42 int numberOfScores = a.size();
43 if (numberOfScores > 0)
44 {
45 return (total/numberOfScores);
46 }
47 else
48 {
49 System.out.println("ERROR: Trying to average 0 numbers.");
50 System.out.println("computeAverage returns 0.");
51 return 0;
52 }
53 }

Because of automatic boxing, we can treat
values of type double as if their type
were Double .

A for-each loop is the nicest way to
cycle through all the elements in an
ArrayList .

54 /**
55 Gives screen output showing how much each of the elements
56 in a differ from their average .
57 */
58 public static void showDifference(ArrayList<Double> a)
59 {
60 double average = computeAverage(a);
61 System.out.println("Average of the " + a.size()
62 + " scores = " + average);
63 System.out.println("The scores are:");
64 for (Double element : a)
65 System.out.println(element + " differs from average by "
66 + (element — average));
67 }
68 }

(continued)