GRAPHICS - Introduction to Java Programming - page 485

13.4 Case Study: The FigurePanel Class
This case study develops the FigurePanel class for displaying various figures.

Key
Point

This example develops a useful class for displaying various figures. The class enables the user
to set the figure type and specify whether the figure is filled, and it displays the figure on a
panel. The UML diagram for the class is shown in Figure 13.8. The panel can display lines,
rectangles, round-cornered rectangles, and ovals. Which figure to display is decided by the
type property. If the filled property is true , the rectangle, round-cornered rectangle, and
oval are filled in the panel.

VideoNote

The FigurePanel class

javax.swing.JPanel

FigurePanel

LINE, RECTANGLE,
ROUND_RECTANGLE, and OVAL are
constants, indicating the figure type.

+LINE = 1
+RECTANGLE = 2
+ROUND_RECTANGLE = 3
+OVAL = 4
-type: int
-filled: boolean

Specifies the figure type (default: 1).
Specifies whether the figure is filled (default: false).

+FigurePanel()
+FigurePanel(type: int)
+FigurePanel(type: int, filled: boolean)
+getType(): int
+setType(type: int): void
+isFilled(): boolean
+setFilled(filled: boolean): void

Creates a default figure panel.
Creates a figure panel with the specified type.
Creates a figure panel with the specified type and filled property.
Returns the figure type.
Sets a new figure type.
Checks whether the figure is filled with a color.
Sets a new filled property.

F IGURE 13.8 FigurePanel displays various types of figures on the panel.

The UML diagram serves as the contract for the FigurePanel class. The user can use the
class without knowing how the class is implemented. Let us begin by writing a program in
Listing 13.2 that uses the class to display six figure panels, as shown in Figure 13.9.
L ISTING 13.2 TestFigurePanel.java
1 import java.awt.*;
2 import javax.swing.*;
3
4 public class TestFigurePanel extends JFrame {
5 public TestFigurePanel() {
6 setLayout( new GridLayout( 2 , 3 , 5 , 5 ));
7 add( new FigurePanel(FigurePanel.LINE));
8 add( new FigurePanel(FigurePanel.RECTANGLE));
9 add( new FigurePanel(FigurePanel.ROUND_RECTANGLE));
10 add( new FigurePanel(FigurePanel.OVAL));
11 add( new FigurePanel(FigurePanel.RECTANGLE, true ));
12 add( new FigurePanel(FigurePanel.ROUND_RECTANGLE, true ));
13 }
14
15 public static void main(String[] args) {
16 TestFigurePanel frame = new TestFigurePanel();
17 frame.setSize( 400 , 200 );
18 frame.setTitle( "TestFigurePanel" );

create figures