Question

Getting a NullPointerException when calling method fillDBWeek(String mName). I can not spot where I am going wrong can some one please help me?

This is the error I am getting for the following method

*Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at View.LectureReport.fillDBWeek(LectureReport.java:49)
    at View.LectureReport$2.actionPerformed(LectureReport.java:96)*

Method fillDBWeek

public void fillDBWeek(String mName)
    {
         tableModel.setDataVector(lRHand.popuSDataWeek(mName), columnNames);
         table.setModel(tableModel);
         table.repaint(); 
    }

Where the method is called when pressing button

JButton btnViewReport = new JButton("View Report");
    btnViewReport.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
            String moduleName = (String)comboBox.getSelectedItem();
            if(comboBox_1.getSelectedItem().equals("Week"))
            {
                fillDBWeek(moduleName);
            }
            else if (comboBox_1.getSelectedItem().equals("Semester"))
            {
                fillDBSem(moduleName);
            }
            else if (comboBox_1.getSelectedItem().equals("Year"))
            {
                fillDBYear(moduleName);
            }
        }
    });

Query using to call the data from SQL database

public Object[][] popuSDataWeek(String moduleName)
{
    data = new Object[30][9];

    try{
           Class.forName(DRIVER_CLASS);

            connection = DriverManager.getConnection( url,"polk", "mire");

            statement = connection.createStatement();
            results = statement.executeQuery("SELECT * FROM Group6_StudAttWeek WHERE module = '"+ moduleName +"'");
            int i=0;
            while(results.next())
            {
            data[i][0]= results.getString("firstname");
            data[i][1]= results.getString("lastname");
            data[i][2]= results.getString("module");
            data[i][3] = results.getString("yearOfStudy");
            data[i][4]= results.getInt("workshop%");
            data[i][5]= results.getInt("tutorial%");
            data[i][6] = results.getInt("lecture%");
            data[i][7] = results.getInt("avg%");
            data[i][8] = results.getInt("number");
            i++;
            }
       results.close();
       statement.close();
       connection.close();
       } catch (SQLException sqlException) {
       sqlException.printStackTrace();
       System.exit(1);
       }catch(Exception exception) {
       System.err.println("An error happened");
       System.exit(1);
       }

    return data;
}

Answer 1

Based on the stack:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at View.LectureReport.fillDBWeek(LectureReport.java:49)
    at View.LectureReport$2.actionPerformed(LectureReport.java:96)

The exception rises in fillDBWeek, either because tableModel or table are null. If the exception is thrown by popuSDataWeek, instead, it should be present on the stacktrace, but anyway the only probable null object I see is connection.

Please, make sure the proper objects are declared and initialized before using them.