Stored procedures doubts

Hai everybody,

Hai,
Currently, I'm at the work of converting database from Oracle to Postgresql.
I have some doubts:

1) What is the equivalent of Oracle ROWNUM in Postgresql? If there is no such equivalent, can U give me an idea about that?
2) How to replace stored procedures with many OUT parameters? I want to call the procedure from Java code.
Please tell me the way to return the values of OUT parameters returned previously by Oracle, from the plpgsql code.
It's very urgent. Please reply quickly with some code examples.

HOW to handle the values returned by the Oracle OUT parameters, in Postgresql?
i.e, how to return the Oracle OUT parameters' values to the calling Java code, in postgresql.
If anybody knows, please explain with suitable examples with plpgsql code and also the Calling Java code.

3) Can default values be assigned to postgresql function parameters? If yes, how?

Thanks in advance.
Senthil.