Displaying Diagnostics to the Standard Output and Error Streams Practical Considerations when Writing Applets Displaying Diagnostics to the Standard Output and Error Streams Displaying diagnostics to the standard output can be an invaluable tool when you're debugging an applet. Another time you'll see messages at the standard output is when an uncaught exception occurs in an applet.
Applets also have the option of using the standard error stream.
When you launch the Applet Viewer from a UNIX shell window, for example, strings displayed to the standard output and error appear in that shell window, unless you redirect the output. When you launch the Applet Viewer from an X Windows menu, the standard output and error go to the console window. Netscape Navigator 2.0, on the other hand, always displays applet standard output and error to the Java Console, which is available from the Options menu. If you have a timing-related problem, printing messages to either of these streams might not be helpful. You should be sure to disable all debugging output before you release your applet.