— Scott McNealy, Sun Microsystems Chairman, President and ceo

g.setColor(randomColor);
g.fillOval(70,70,100,100);
}
fill the entire panel with black 
(the default color)
The first two args define the (x,y) upper left 
corner, relative to the panel, for where drawing 
starts, so 0, 0 means “start 0 pixels from the 
left edge and 0 pixels from the top edge.” The 
other two args say, “Make the width of this 
rectangle as wide as the panel (this.width()), and 
make the height as tall as the panel (this.height)”
your file name goes here
The x,y coordinates for where the picture’s top 
left corner should go. This says “3 pixels from 
the left edge of the panel and 4 pixels from the 
top edge of the panel”. These numbers are always 
relative to the widget (in this case your JPanel 
subclass), not the entire frame.
start 70 pixels from the left, 70 from 
the top, make it 100 pixels wide, and 
100 pixels tall.
You can make a color by passing in 3 ints 
to represent the RGB values. 
Display a JPEG
Paint a randomly-colored circle 
on a black background

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366
 
chapter 12
The argument to paintComponent() is declared as type 
Graphics (java.awt.Graphics).
Behind every good Graphics reference 
is a Graphics2D object.
drawing gradients with 
Graphics2D
public void paintComponent(Graphics g) { }
Methods you can call on a 
Graphics
reference:
drawImage()
drawLine()
drawPolygon
drawRect()
drawOval()
fillRect()
fillRoundRect()
setColor()
So the parameter ‘g’ IS-A Graphics object. Which means it 
could be a subclass of Graphics (because of polymorphism). 
And in fact, it is. 
The object referenced by the ‘g’ parameter is actually an