Java Reference
In-Depth Information
8
private
int
x1;
// x-coordinate of first endpoint
9
private
int
y1;
// y-coordinate of first endpoint
10
private
int
x2;
// x-coordinate of second endpoint
11
private
int
y2;
// y-coordinate of second endpoint
12
private
Color color;
// color of this line
13
14
// constructor with input values
15
public
MyLine(
int
x1,
int
y1,
int
x2,
int
y2, Color color)
16
{
17
this
.x1 = x1;
18
this
.y1 = y1;
19
this
.x2 = x2;
20
this
.y2 = y2;
21
this
.color = color;
22
}
23
24
// Draw the line in the specified color
25
public
void
draw(Graphics g)
26
{
27
g.setColor(color);
28
g.drawLine(x1, y1, x2, y2);
29
}
30
}
// end class MyLine
Fig. 8.17
|
MyLine
class represents a line. (Part 2 of 2.)
Class
DrawPanel
In Fig. 8.18, we declare class
DrawPanel
, which will generate random objects of class
MyLine
. Line 12 declares the
MyLine
array
lines
to store the lines to draw. Inside the con-
structor (lines 15-37), line 17 sets the background color to
Color.WHITE
. Line 19 creates
the array with a random length between 5 and 9. The loop at lines 22-36 creates a new
MyLine
for every element in the array. Lines 25-28 generate random coordinates for each
line's endpoints, and lines 31-32 generate a random color for the line. Line 35 creates a
new
MyLine
object with the randomly generated values and stores it in the array. Method
paintComponent
iterates through the
MyLine
objects in array
lines
using an enhanced
for
statement (lines 45-46). Each iteration calls the
draw
method of the current
MyLine
object
and passes it the
Graphics
object for drawing on the panel.
1
// Fig. 8.18: DrawPanel.java
2
// Program that uses class MyLine
3
// to draw random lines.
4
import
java.awt.Color;
5
import
java.awt.Graphics;
6
import
java.security.SecureRandom;
7
import
javax.swing.JPanel;
8
9
public
class
DrawPanel
extends
JPanel
10
{
11
private
SecureRandom randomNumbers =
new
SecureRandom();
12
private
MyLine[] lines;
// array of lines
Fig. 8.18
|
Program that uses class
MyLine
to draw random lines. (Part 1 of 2.)
