In many programs, you need to use numerical constants - values that do not change and that have a special signification for a computation.
It is a good idea to use symbolic names for all values, even those that appear obvious.
Consider the following links:
a) Keyword final
b) Convention
c) Static constants
d) Math class and its constants
or
n) or next to More on Operators
r) or back to More on primitive types
x) or out to More on Variables and Data Types