function in derby[beginner]

[tony_se]

I have this class:
public class Say {
public static int say(int i) {
System.out.println("* Say: " + i);
return i;
}

public static int say2(String msg) {
System.out.println("** " + msg);
return 1;
}
}

and I created a function in Derby:
create function say2(msg varchar(50)) returns integer
parameter style java no sql language java
external name 'Say.say2';

but when I want to use it, error occurs:
ERROR 42X50: No method was found that matched the method call
Say.say2(java.lang
..String), tried all combinations of object and primitive types and any
possible
type conversion for any parameters the method call may have. The
method might e
xist but it is not public and/or static, or the parameter types are
not method i
nvocation convertible.

And I created another function:
create function say(i integer) returns integer
parameter style java no sql language java
external name 'Say.say';

It works fine.

I've tried hard to figure it out but failed. Can anybody help me?

Thank you in advance!!!