表不会显示列名，从我的数据库中获取信息将不起作用

Question

我在从数据库导入数据时遇到问题，因为当我没有看到编码问题时，我收到NullPointer异常。当我使用二维数组时，我的表中的列名也不会显示，这也会在从数据库显示数据时引起问题。有问题吗？提前谢谢

//Says 'Connection class doesn't exist' yet works in another class I made called Queries
final String URL="jdbc:mysql://localhost:3306/aerogames";
final String DRIVER="com.mysql.jdbc.Driver";
final String USERNAME="root";
final String PASSWORD="";

Connection conn=null;
Statement st=null;
String query;

/

public void GameMenu(){
    {
        GameCard=new JPanel();
        GameCard.setLayout(gridBag);

        tableLabel=new JLabel("MANAGE AUTHOR");

        insertTable=new JButton("Insert Game");
        updateTable=new JButton("Update Game");
        deleteTable=new JButton("Delete Game");
        backTable=new JButton("Go to Main Menu");
        backTable.addActionListener(this);
        Object[] col={"Author ID","First Name","Last Name"};

        DefaultTableModel model = new DefaultTableModel(data,col);
        table=new JTable(model)
        {
            boolean[] cellEditables={false,true,true, true}; 

            public boolean isCellEditable(int row,int col)
            {
                return cellEditables[col];
            }
        };

        table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);        
        scroll=new JScrollPane(table);
        scroll.setPreferredSize(new Dimension(350,200));

        model=new DefaultTableModel(data,col);
        table.setModel(model);

        //             insertBtn.addActionListener(new ActionListener()
        //                 {
        //                     public void actionPerformed(ActionEvent evt)
        //                     {
        //                         insertAuthor();
        //                     }
        //                 });
        //             updateBtn.addActionListener(new ActionListener()
        //                 {
        //                     public void actionPerformed(ActionEvent evt)
        //                     {
        //                         updateAuthor();
        //                     }        
        //                 });
        //             deleteBtn.addActionListener(new ActionListener()
        //                 {
        //                     public void actionPerformed(ActionEvent evt)
        //                     {
        //                         deleteAuthor();
        //                     }            
        //                 });        

        createTable();
        updateTable();

        addComponent(tableLabel,GameCard,0,0,0,0,0,0);
        addComponent(scroll,GameCard,0,1,0,0,0,0);
        c.gridwidth=1;
        addComponent(insertTable,GameCard,0,2,0,0,0,0);
        addComponent(updateTable,GameCard,0,3,0,0,0,0);
        addComponent(deleteTable,GameCard,0,4,0,0,0,0);
        addComponent(backTable,GameCard,0,5,0,0,0,0);

    }
}

/

 public void createTable()
{
    model=new DefaultTableModel();
    table=new JTable(model)
    {
        boolean[] cellEditables={false,true,true, true}; 

        public boolean isCellEditable(int row,int col)
        {
            return cellEditables[col];
        }
    };

    table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);        
    scroll=new JScrollPane(table);
    scroll.setPreferredSize(new Dimension(350,200));
}

public void updateTable()
{        
    Object[][] data=q.getAllGamesByID_OA();
    Object[] colNames={"Game ID","Game Name","Game Price", "Game Stock"};
    model=new DefaultTableModel(data,colNames);
    table.setModel(model);
}  

/空指针异常错误

public Object[][] getAllGamesByID_OA()
{
    query="select * from product_details order by product_ID";
    Object[][] data=null;
    ResultSet rs;
    try
    {
        rs=st.executeQuery(query);
        rs.last();
        int rowCount=rs.getRow();
        rs.beforeFirst();
        data=new Object[rowCount][4];
        int i=0;
        while(rs.next())
        {
            data[i][0]=rs.getInt("product_ID");
            data[i][1]=rs.getString("product_name");
            data[i][2]=rs.getInt("unit_price");
            data[i][3]=rs.getInt("quantity_in_stock");
            i++;
        }
    }
    catch(SQLException e)
    {
        JOptionPane.showMessageDialog(null,e.getMessage(),
            "SQL Error",JOptionPane.INFORMATION_MESSAGE);
    }
    return data;
}