When you are running an applet in the IDE's Applet Viewer, you can edit the applet's source code and then see the results of your changes immediately.
To make a change to a running applet:
The applet will start running at the beginning, with the new change incorporated.
Running an applet from the IDE
Creating an applet or application
Creating a quick, basic sample applet or application
Saving changes to code
Debugging during the development cycle with the integrated debugger
Experimenting with code fragments