DB2 java Stored Procedure call return error SQLCODE=-440, SQLSTATE=42884

I am doing a simple stored procedure call to DB2. While it calls the stored procedure, it always returns this error:

DB2 SQL Error: SQLCODE=-440, SQLSTATE=42884, SQLERRMC=MEDIAN_RESULT_SET;PROCEDURE, DRIVER=3.66.46

========== Java code:

String JDBC_DRIVER = "com.ibm.db2.jcc.DB2Driver";
// STEP 2: Register JDBC driver
Class.forName(JDBC_DRIVER);

// STEP 3: Open a connection
System.out.println("Connecting to database..."); 
conn = DriverManager.getConnection(DB_URL, USER, PASS);

// to execute the stored procedure.
System.out.println("CALL median_result_set(?)");
String sql = "CALL median_result_set(?)";
CallableStatement stmt1 = conn.prepareCall(sql);
stmt1.registerOutParameter(1, Types.DOUBLE);

stmt1.execute();
System.out.println("jdbcadapter->callproc after execute " + sql);
stmt1.close();

conn.close();

============== The db2 clp command line worked:

c:SP>db2 call median_result_set(?)
 Value of output parameters 
 --------------------------
 Parameter Name  : MEDIANSALARY 
 Parameter Value : +7.68582000000000E+004

Result set 1
--------------
NAME      JOB   SALARY
--------- ----- ---------
Marenghi  Mgr    77506.75
O'Brien   Sales  78006.00

================ The stored procedure definition:

CREATE PROCEDURE median_result_set
-- Declare medianSalary as OUT so it can be used to return values
(OUT medianSalary DOUBLE)
RESULT SETS 2
LANGUAGE SQL
BEGIN

   DECLARE v_numRecords INT DEFAULT 1;
   DECLARE v_counter INT DEFAULT 0;

   DECLARE c1 CURSOR FOR
      SELECT salary FROM staff
       ORDER BY CAST(salary AS DOUBLE);

  -- use WITH RETURN in DECLARE CURSOR to return a result set
  DECLARE c2 CURSOR WITH RETURN FOR
   SELECT name, job, salary
   FROM staff 
   WHERE CAST(salary AS DOUBLE) > medianSalary
   ORDER BY salary;

  -- use WITH RETURN in DECLARE CURSOR to return another result set
 DECLARE c3 CURSOR WITH RETURN FOR
    SELECT name, job, salary
    FROM staff
    WHERE CAST(salary AS DOUBLE) < medianSalary
    ORDER BY SALARY DESC;

 DECLARE CONTINUE HANDLER FOR NOT FOUND
   SET medianSalary = 6666; 

 -- initialize OUT parameter
 SET medianSalary = 0;

 SELECT COUNT(*) INTO v_numRecords FROM STAFF;

 OPEN c1;

   WHILE v_counter < (v_numRecords / 2 + 1) DO
     FETCH c1 INTO medianSalary;
     SET v_counter = v_counter + 1;
  END WHILE;
  CLOSE c1;

  -- return 1st result set, do not CLOSE cursor
  OPEN c2;

  -- return 2nd result set, do not CLOSE cursor
  OPEN c3;
END @