You can call a Java stored function from a SQL statement as shown below.
select Hello() from db_root;
select sp_int(99) from db_root;
You can use a host variable for the IN/OUT data type when you call a Java stored function/procedure as follows:
SELECT 'Hi' INTO :out_data FROM db_root;
CALL test_out(:out_data);
SELECT :out_data FROM db_root;
The first clause calls a Java stored procedure in out mode by using a parameter variable; the second is a query clause retrieving the assigned host variable out_data.