The following program will print »Hello!«.

public class Hello
{ public static void main( final java.lang.String[] args )  
 { java.lang.System.out.println( "Hello!" ); }}

 This trick works by exploiting the JLS and the Java-API,
 forcing the JVM to print »Hello!«. Both the Java Security
 manager and the Java "sandbox" usually will not prevent this
 to be actually executed!

 But be careful: The text will be printed /immediatly/ as soon
 as the program is started, there will not be a prior warning
 or a an inquiry. So, you might not try this at home. But
 possibly you could fool your friends in the chat room into
 compiling and running it? That would be fun! I'd like to see
 the baffled look on their faces when suddenly out of the blue
 the text »Hello!« appears on their screen.

 Even more cool: The text »Hello!« can be replaced by any other
 text, in order to print that other text. So it is great for
 playing around. Just give it a try!