Introduction to Java Programming - Building Java Programs: A Back to Basics Approach - page 34

program uses the drawBox method to produce the same output as the original
DrawBoxes program:
1 public class DrawBoxes2 {
2 public static void main(String[] args) {
3 drawBox();
4 System.out.println();
5 drawBox();
6 }
7
8 public static void drawBox() {
9 System.out.println("+------+");
10 System.out.println("| |");
11 System.out.println("| |");
12 System.out.println("+------+");
13 }
14 }
Flow of Control
The most confusing thing about static methods is that programs with static methods
do not execute sequentially from top to bottom. Rather, each time the program
encounters a static method call, the execution of the program “jumps” to that static
method, executes each statement in that method in order, and then “jumps” back to
the point where the call began and resumes executing. The order in which the state-
ments of a program are executed is called the program's flow of control.
Flow of Control
The order in which the statements of a Java program are executed.
Let's look at the control flow of the DrawBoxes2 program shown previously. It has
two methods. The first method is the familiar main method, and the second is
drawBox . As in any Java program, execution starts with the main method:
public static void main(String[] args) {
drawBox();
System.out.println();
drawBox();
}
In a sense, the execution of this program is sequential: Each statement listed in the
main method is executed in turn, from first to last.
But this main method includes two different calls on the drawBox method. This
program will do three different things: execute drawBox , execute a println , then
execute drawBox again.