JDeveloper, Java & XML :: Create Or Replace And Compile Java - Getting Ora 29531?

I've this java source create or replace and compile java source named "Decodificador" as
public class Decodificador {
public static String decodifica(String codigo)
return codigo;

and this function

create or replace function F_Decodificador(codigo varchar2) RETURN VARCHAR2 IS
LANGUAGE java NAME 'Decodificador.decodifica(String) return String';

when I execute the function the result is:

ORA-29531: no method decodifica in class Decodificador