import java.sql.*;

public class cursorInfo {

    public static String getColumnNames (ResultSet cur) 
        throws SQLException 
    {
        String ret = "";
        ResultSetMetaData curMeta = cur.getMetaData();
        int colCount = curMeta.getColumnCount();
        for (int i=1; i <= colCount; i++) {

            ret = ret + " " + curMeta.getColumnName(i);
        }
        
        return ret;
    }
}


First attempt:
sql->create or replace package csrInfo
  2  as
  3  
  4  
  5  function getColumnNames(rc in sys_refcursor)
  6  return varchar2
  7  as language java
  8  name 'cursorInfo.getColumnNames(oracle.jdbc.driver.ResultSet) return String';
  9  --name 'cursorInfo.getColumnNames(java.sql.ResultSet) return String';
 10  
 11  
 12  end;
 13  /

Package created.

Elapsed: 00:00:00.01
sql->show err
No errors.
sql->
sql->declare
  2      rc      sys_refcursor;
  3      cols    varchar2(100);
  4  begin
  5      open rc for
  6          select 1 xx, 2 rtr, 3 qwerty
  7            from dual;
  8  
  9      cols := csrInfo.getColumnNames(rc);
 10      dbms_output.put_line(cols);
 11  end;
 12  /
declare
*
ERROR at line 1:
ORA-29531: no method getColumnNames in class cursorInfo
ORA-06512: at "PROG.CSRINFO", line 5
ORA-06512: at line 9


Elapsed: 00:00:01.20


156th attempt:


sql->create or replace package csrInfo
  2  as
  3  
  4  
  5  function getColumnNames(rc in sys_refcursor)
  6  return varchar2
  7  as language java
  8  --name 'cursorInfo.getColumnNames(oracle.jdbc.driver.ResultSet) return String';
  9  name 'cursorInfo.getColumnNames(java.sql.ResultSet) return String';
 10  
 11  
 12  end;
 13  /

Package created.

Elapsed: 00:00:00.10
sql->show err
No errors.
sql->
sql->declare
  2      rc      sys_refcursor;
  3      cols    varchar2(100);
  4  begin
  5      open rc for
  6          select 1 xx, 2 rtr, 3 qwerty
  7            from dual;
  8  
  9      cols := csrInfo.getColumnNames(rc);
 10      dbms_output.put_line(cols);
 11  end;
 12  /
XX RTR QWERTY

PL/SQL procedure successfully completed.

Elapsed: 00:00:01.57