java.lang.NullPointerException

[Dorota Rupniewska]

Hello 2 All

My code is really simple, but I get java.lang.NullPointerException

Statement s = conn.createStatement(); ResultSet r = s.executeQuery("SELECT * FROM sale_daty WHERE data='"+ fDate +"';"); while(r.next()){ if(r.getInt("idSali") == fSala){ ok = false; } else{ ok = true; }

and table sale_daty:
Statement st = connection.createStatement(); st.executeUpdate("CREATE TABLE sale_daty (idSD INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY, " + "idSali INTEGER, " + "data TIMESTAMP(10));");

fDate is a parameter (Date). fSala is Integer.
All I want is to check if fDate is already in database. If yes, then check if idSali from this recordset = fSala
Is anyone can help?

[Jan Cumps]

Welcome to the Ranch, Dorata.
At which line is the Exception thrown?

[Tom Reilly]

It would help if you post all of your code rather than just snippets and post the full exception trace that says which line of code is causing the NPE. Do you know how to do that? Otherwise, we can only guess. My guess is that either the variable(s) conn or fDate has not been initialized.

[Ronald Djunaedi]

Hi Dorota, i hope you dont mind to post a full exception output, since it's hard enough to identify the problem only with the code you posted here...

[Campbell Ritchie]

Welcome to JavaRanch Dorota Rupniewska

Please don't write things like "2" for "to".

[Dorota Rupniewska]

It's bigger project but I try explain It better:
I have a calendar in a JSP page:

<%
     for(int i=1;i<=iTotalweeks;i++){%>
       <tr><%
            for(int j=1;j<=7;j++){
                if(cnt<start || (cnt-start+1)>liczbaDni){%>
                  <td align="center" height="25" class="dsb"> </td><%}
                else{
                  if(spr.sprawdzWolnyTermin(kalSala, Integer.parseInt(kalRok), kalMies, (cnt-start+1))){%>
                     <td style="background-color: red;" align="center" height="25" id="day_<%=(cnt-start+1)%>"><span><%=(cnt-start+1)%></span></td><%}
                  else{%>
                     <td style="background-color: #c7c7c7;" align="center" height="25" id="day_<%=(cnt-start+1)%>"><span><%=(cnt-start+1)%></span></td><%}
                }
    cnt++;
 }%>
    </tr><%}%>

When user change month, days which are in database should be marked red. The rest of my code:

public boolean sprawdzWolnyTermin(String fSala, int fRok, int fMies, int fDzien) throws ParseException{

        Calendar cal = new GregorianCalendar();
        
        cal.set(Calendar.YEAR, fRok);
        cal.set(Calendar.MONTH, fMies);
        cal.set(Calendar.DAY_OF_MONTH, fDzien);

        String sf = new SimpleDateFormat("yyyy-MM-dd 00:00:00").format(cal.getTime());
        SimpleDateFormat formater = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        Date date = new Date();
        date = formater.parse(sf);

        return baza.czyDostepna(baza.idSali(fSala), date);
    }

public boolean czyDostepna(int fNumer, Date fData){ boolean ok = true; try{ Statement s = connection.createStatement(); ResultSet r = s.executeQuery("SELECT * FROM sale_daty WHERE data='"+ fDate +"';"); r.first(); while(r.next()){ if(r.getInt("idSali") == fSala){ ok = false; } else{ ok = true; } } catch(Exception e){ System.out.println(e); } return ok; }

This function always return true so all days are marked red.
To find what's wrong I've changed and shorted this code to:

public static void main(String[] args) {

        Connection conn = null;
                
        try{
           Class.forName("com.mysql.jdbc.Driver");
           String url = "jdbc:mysql://localhost/rezerwacje";
           String login = "*******";
           String password = "*********";
           conn = DriverManager.getConnection(url,login,password);
           Statement st = conn.createStatement();
         
           boolean ok = false;
           int fNumer = 5;

           String dd = "2012-01-01 00:00:00";
           
           java.sql.Timestamp fData = Timestamp.valueOf(dd);
           
           ResultSet r = st.executeQuery("SELECT * FROM sale_daty WHERE data='"+ fData +"';");
            r.first();
            while(r.next()){
                if(r.getInt("idSali") == fNumer){
                    Date tmpDate = r.getDate("data");
                    if(tmpDate.equals(fData)){
                        ok = false;
                    }
                }
                else{
                    ok = true;
                }
            }

            System.out.println(ok);

       }
       catch(Exception e){
           System.out.println(e);
       }
   }

This short code work fine and there is no NPE. I guess the parameter fDate wasn't in proper format.
Thank you for help

P.S.

Please don't write things like "2" for "to".

ok, I won't do this again