The example Java program wrote the words "Hello World!" in the command interpreter window.
Your program may not have run correctly.
It is possible that you did not type in exactly the characters that were
required.
The spaces don't particularly matter.
But check especially characters like
[
and {
and (
and "
.
You have to use the correct ones.
Fuss around for a while to get the program to work. If you just can't get it to work, give up and move on. Probably there is some trival detail that you have overlooked and will see clearly later on. This happens all the time in programming.
If everything worked out perfectly, then go back and do something wrong. This will help you understand what happened later on when you do something wrong, but didn't intend to.
Had enough, for now?