Question

i try to insert data from database to Jtable
there is my code:

private Vector <Vector<String>> data;
private Vector<String> header;
table.setModel(new javax.swing.table.DefaultTableModel(
data,header     
));

GtFromDb db=new GtFromDb();
data=db.getClient();

header=new Vector<String>();
header.add("Imones pavadinimas");
header.add("vardas");
header.add("pavarde");
header.add("salis");
header.add("Adresas");
header.add("telefonas");

public Vector getClient() 
{
    Vector <Vector<String>> clientVector=new Vector<Vector<String>>();  
    try
    {
         PreparedStatement zadanie = connect.prepareStatement("SELECT * FROM Clients");
         dane = zadanie.executeQuery();
         while(dane.next()) {
             Vector <String> client=new Vector<String>();
             String imonesPav=dane.getString("Imones_pavadinimas");
             String vardas = dane.getString("Vardas");
             String pavarde = dane.getString("Pavarde");
             String salis = dane.getString("Salis");
             String adresas=dane.getString("Adresas");
             String telefonas = dane.getString("Telefonas");
             if (imonesPav != null) {
                 imonesPav = imonesPav.trim();
                 client.add(imonesPav);
             }
             if (vardas != null) {
                 vardas = vardas.trim();
                 client.add(vardas);
             }
             if (pavarde != null) {
                 pavarde = pavarde.trim();
                 client.add(pavarde);
             }
             if (salis != null) {
                 salis = salis.trim();
                 client.add(salis);
             }
             if (adresas != null) {
                 adresas = adresas.trim();
                 client.add(adresas);
             }
             if (telefonas != null) {
                 telefonas = telefonas.trim();
                 client.add(telefonas);
             }
        }
        zadanie.close();
    }
    catch(SQLException e){}
        return clientVector;    
    }

it thorows me error:

java.lang.NullPointerException
at test$GtFromDb.getClient(test.java:108)
at test.<init>(test.java:49)
at test.main(test.java:24)

where is problem?

Answer 1

you forgot to added and another …

1) client=new Vector<String>(); to the DefaultTableModel inside loop while(dane.next()) {...}

2) public Vector getClient() must be initialized return null

3) change public Vector getClient() to public void getClient(), remove return statement

4) PreparedStatement zadanie must be closed in finally block try- catch - finally

5) dane = zadanie.executeQuery(); looks like as Resultset, and same as PreparedStatement zadanie must be closed in finally block

6) JTable and Vector can hold null value

7) if you are only to want to display data from DbTable to the JTable then look for ResultsetTableModel, TableFromDatabase, you can search for that on this forum too