Java How to Program Fourth Edition - DCC

Chapter 5 Control Structures: Part 2 217
Fig. Fig. 5.9 5.9 5.9 Using the do/while repetition structure (part 2 of 2).
In method paint (lines 13–26), line 18 declares control variable counter and initializes
it to 1. Upon entering the do/while structure, lines 21–22 send the drawOval
message to the Graphics object to which g refers. The four arguments that represent the
upper left x-coordinate, upper left y-coordinate, width and height of the oval’s bounding
box (an imaginary rectangle in which the oval touches the center of all four sides of the rectangle)
are calculated based on the value of counter. The program draws the innermost
oval first. The bounding box’s upper left corner for each subsequent oval moves closer to
the upper left corner of the applet. At the same time, the width and height of the bounding
box are increased, to ensure that each new oval contains all the previous ovals. Line 23
increments counter. Then, the program evaluates the loop-continuation test at the
bottom of the loop. The do/while flowchart in Fig. 5.10 makes it clear that the program
does not evaluate the loop-continuation condition until after the action executes once.
action(s)
condition
false
true
Fig. Fig. Fig. 5.10 5.10 5.10 Flowcharting the do/while repetition structure.
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