Primitive Data and Definite Loops - Building Java Programs: A Back to Basics Approach - page 108

These definitions create constants called HEIGHT and WIDTH that will always have
the values 10 and 20 . These are known as class constants, because we declare them
in the outermost scope of the class, along with the methods of the class. That way,
they are visible in each method of the class.
We've already mentioned that we can avoid using a magic number in the DrawCone
program by introducing a constant for the number of lines. Here's what the constant
definition looks like:
public static final int LINES = 5;
We can now replace the 5 in the outer loop with this constant and replace the 11
in the second inner loop with the expression 2 * LINES + 1 . The result is the fol-
lowing program:
1 public class DrawCone2 {
2 public static final int LINES = 5;
3
4 public static void main(String[] args) {
5 for ( int line = LINES; line >= 1; line--) {
6 for ( int i = 1; i <= (line - 1); i++) {
7 System.out.print(" ");
8 }
9 int stars = 2 * LINES + 1 - 2 * line;
10 for ( int i = 1; i <= stars; i++) {
11 System.out.print("*");
12 }
13 System.out.println();
14 }
15 }
16 }
Notice that in this program the expression for the number of stars has become suf-
ficiently complex that we've introduced a local variable called stars to store the
value. The advantage of this program is that it is more readable and more adaptable.
A simple change to the constant LINES will make it produce a figure with a different
number of lines.
2.5 Case Study: Hourglass Figure
Now we'll consider an example that is even more complex. To solve it, we will follow
three basic steps:
1. Decompose the task into subtasks, each of which will become a static method.
2. For each subtask, make a table for the figure and compute formulas for each
column of the table in terms of the line number.
3. Convert the tables into actual for loop code for each method.