04 Applets

A Java applet is a Java program which adheres to specific conventions that
allow it to run within a Java - enabled browser.  Java applets can also be
viewed in a free program called appletviewer.

A web page can download an applet from a server, then run the applet
within a window as defined by the calling HTML statements :

------ Sample applet

import java.awt.Graphics;
public class MyApplet extends Applet {
   public void paint (Graphics g) {
     g.drawString( "Have a nice day." , 50,25);
   }
}

----- Sample calling HTML file

< html >
< head >
< title > Applet Template </ title >
</ head >
< body >
< hr >
< applet code = "MyApplet.class" Width = 200 Height = 200 >
< param Name = message  Value = "string" >
</ applet >
< hr >
</ body >
</ html >

--------- Applet tags ( for use in HTML file)

< applet > ...   </ applet >

Code        - Name of the applet (does not include path), case - sensitive
CodeBase    - Options - relative path to the class (could be URL)
Width       - Pixel width of frame that holds the applet
Height      - Pixel height of frame that holds the applet
Align       -
HSpace      - border space around the applet (pixels)
VSpace      - border space around the applet (pixels)

You can pass parameters, each within its own tag :
- name is case - sensitive :
- all values are sent as strings
- go between the < applet > and </ applet > tags

< param Name = "parameter_name" Value = "parameter_value" >

For non - Java - compatible browsers, you can include the
< img > tag (just before the </ applet > tag is preferred).
If the browser cannot read the < applet > it will display
the image.  Make sure the image is same size / location as
the applet.

------- Freeware applet viewer

Applets can be viewed in a freeware application called appletviewer :
- reads an HTML file and runs only the applet
- if the page has multiple applets, all are run in own instance of appletviewer

appletviewer sample.html