GRAPHS AND APPLICATIONS - Introduction to Java Programming: Comprehensive Version - page 1059

**28.21

( Display sets of connected circles ) Modify Listing 28.10,
ConnectedCircles.java, to display sets of connected circles in different colors.
That is, if two circles are connected, they are displayed using the same color;
otherwise, they are not in same color, as shown in Figure 28.25. ( Hint : See
Programming Exercise 28.4.)

(a) (b) (c)

F IGURE 28.25

(a) Connected circles are displayed in the same color. (b) Rectangles are not filled with a color if they are
not connected. (c) Rectangles are filled with a color if they are connected.

*28.22

( Move a circle ) Modify Listing 28.10, ConnectedCircles.java, to enable the
user to drag and move a circle.

**28.23

( Connected rectangles ) Listing 28.10, ConnectedCircles.java, allows the user
to create circles and determine whether they are connected. Rewrite the pro-
gram for rectangles. The program lets the user create a rectangle by clicking a
mouse in a blank area that is not currently covered by a rectangle. As the rec-
tangles are added, the rectangles are repainted as filled if they are connected or
are unfilled otherwise, as shown in Figure 28.25b-c.

*28.24

( Remove a circle ) Modify Listing 28.10, ConnectedCircles.java, to enable the
user to remove a circle when the mouse is clicked inside the circle.