Generics and the ArrayList Class - Absolute Java - page 774

EXAMPLE: (continued)

with partially filled arrays. Those details are taken care of for us automatically. The
code for those details is in the definition of the ArrayList class, but there is no need
to look at that code. That code is all implementation detail that we need not worry
about when using an ArrayList .
Notice the use of for-each loops in our program. The cleanest and easiest way to
cycle through all the elements in an ArrayList is to use a for-each loop.
It is instructive to compare the program in Display 14.3, which uses an ArrayList ,
with the program in Display 6.4, which does the same thing but uses an ordinary
array. The version that uses an ArrayList is much cleaner and even much shorter
than the one that uses an ordinary array. This is because an ArrayList does so many
things for you automatically that you would have to explicitly code for if you used
an ordinary array. This is a good example of information hiding and code reuse. The
programmers who defined the ArrayList class did a lot of programming for you so
that your programming task is simpler than it would otherwise be.

Display 14.3 Golf Score Program (part 1 of 3)

1 import java.util.ArrayList;
2 import java.util.Scanner;

3 public class GolfScores
4 {
5 /**
6 Shows differences between each of a list of golf scores and their
average.
7 */
8 public static void main(String[] args)
9 {
10 ArrayList<Double> score = new ArrayList<Double> ();

11 System.out.println("This program reads golf scores and shows");
12 System.out.println("how much each differs from the average.");

13 System.out.println("Enter golf scores:");
14 fillArrayList(score);
15 showDifference(score);
16 }

17 /**
18 Reads values into the array a.
19 */
20 public static void fillArrayList(ArrayList<Double> a)

Parameters of type ArrayList<Double>()
are handled just like any other class parameter.