In Java all drawing takes place via a Graphics object.
This is an instance of the class java.awt.Graphics.
Initially the Graphics object you use will be the
one passed as an argument to an applet's paint()
method. Later you'll see other Graphics objects too.
Everything you learn today about drawing in an applet transfers
directly to drawing in other objects like Panels, Frames, Buttons,
Canvases and more.
Each Graphics object has its own coordinate system,
and all the methods of Graphics including those for
drawing Strings, lines, rectangles, circles, polygons and more.
Drawing in Java starts with particular Graphics
object. You get access to the Graphics object through
the paint(Graphics g) method of your applet. Each draw
method call will look like g.drawString("Hello World", 0,
50) where g is the particular Graphics object with which you're drawing.
For convenience's sake in this lecture the variable g will always refer to a preexisting object of the Graphics class. As with any other method you are free to use
some other name for the particular Graphics context,
myGraphics or appletGraphics perhaps.