The applet console.
Although applets do not have the standard command line console, you can see the non GUI output from an applet via the applet console. In Microsoft IE you can access this from the Tools/Sun Java Console or from Netscape/Mozilla it is visible from Tools/Web Development/Java Console. This can be useful if you load an applet from a web site and it does not appear to work correctly. Typically this can be a failure to locate classes needed in an applet and in my own experience it allowed me to track down an error where I was using classes that the Java Runtime thought was trying to access the local file system.