Applet

Context

You need to run a program inside a web browser. Access to local resources (such as files on the local machine) are not required.

Example

Both Input with Button and Input with TextField are simple examples of applets. What they don't show is the applet tag which must be included in the HTML file which contains the applet. Here is the tag from the page displaying the button example.

<APPLET 
   WIDTH="154" 
   HEIGHT="129"
   CODEBASE="applets/"
   CODE="Patterns.Button.ButtonEx.class">
</APPLET>

Note that the example below uses javax.swing.JApplet, and that the online applet currently uses java.applet.Applet. If you want to use the enhanced swing capabilities then refer to the Applet lab, here.

Pattern

package <PackageName>;
import javax.swing.JApplet;
public class <ClassName> extends JApplet
{  public void init()
   {  <Code To Initialize Applet>}
   public void start()
   {  <Code To Make Applet Start Doing Its Job>} 
   public void stop()
   {  <Code To Temporarily Stop Applet When It's Not Viewable>} 
   public void destroy()
   {  <Code To Execute When Applet Is Permanently Stopped>} 
}

Applet tags required in the HTML file where the applet should appear:

<APPLET 
   WIDTH="<width in pixels>" 
   HEIGHT="<height in pixels>"
   CODEBASE="<location of the applet's package relative to this HTML file"
   CODE="<PackageName>.<ClassName>.class">
</APPLET>

Notes

The four methods shown are all inherited from JApplet and should be overridden with specifics for this applet. It is common for all but init to be empty (and therefore you don't need to override them).
Concatenating the CODEBASE and CODE attributes from the HTML file must give the location of the class files relative to the HTML file. Furthermore, the CODE attribute must correspond to the package and class contained in the named file. For example, if the class file is located in applets/Patterns/ButtonEx/Button.class and the package name is Patterns.ButtonEx then the CODEBASE attribute should be "applets/" and the CODE attribute should be "Patterns.ButtonEx.Button.class".
It is common for all of the class files required by an applet to be included in a single .jar or .zip file. This speeds access since the browser must only make one HTTP connection instead of a connection for each individual class file. When such an archive is used the CODEBASE attribute is replaced by ARCHIVE="<location of archive relative to this HTML file>".

Related Patterns

Graphical Application, for programs which do not need to run in a web browser or need access to local resources.
Console Application, for programs which do not need a graphical user interface.
Summary of Listeners, for a summary of many standard gui widgets and the listeners they use.