java in forms -> Variable BigInteger []

Hi friends am wanting wrapear java code against an Oracle function I write the simple example, it gives me error. if someone could help.

/*I think the java code in Oracle database*/
CREATE OR REPLACE AND COMPILE 
JAVA SOURCE 
NAMED FuentesJava 
AS
import java.math.BigInteger;
import java.util.*;

public class OracleJavaClass
{
public static String Saluda(String nombre){
return ("Hola desde Java" + nombre);
}

public static String descifra(BigInteger[] cifrado) {

return ("hola");
}
}
;

/*wrapeo the generated code against an Oracle function*/

CREATE OR REPLACE 
FUNCTION Saluda_wrap (numero PLS_INTEGER)
RETURN VARCHAR2
AS
LANGUAGE JAVA NAME 
'OracleJavaClass.descifra(java.math.BigInteger) return java.lang.String';