What does @,#,$ stand for?hard stuff

Question

As i have tryed to experiment with java i got stuck and confused meeting with these three characters.
Where can i get any information about them?
@
#
$
In spite of reference problem i count for some answers according to these three signs.

Thanks, Michael

Answer 1

In C and C++ '#' means preprocessor but in java well i never came across it lol

Answer 2

@ - is used for decorators/annotations for example: @Override

$ - stackoverflow.com/questions/7484210/what-is-the-meaning-of-in-a-variable-name here it is explained pretty well

# - I have no idea :/