Abalfazl, I get the impression you are confused about the meaning of \u0633.
Any of the \uxxxx tokens in Java source code will be read by Java's 'precompiler', and automatically converted to their char representation. This all happens before the source code is actually compiled. This is done in the entire file, including comments, strings and other code.
It's simply a way you can enter unicode characters in your source file without being able to type their actual character representation. Outside of the precompiler, these tokens have no meaning.
There is no simplest way of converting \u0633 to س, because they already mean exactly the same thing, as far as Java in concerned.
What is it exactly you want to do?
As for your question regarding UTF-8, what have you found out for yourself?