將項目設置到jComboBox

Question

我知道如何從數據庫獲取數據到Java應用程序，但是我的問題是將數據添加到JComboBox，我這樣做是：main.java：

`Interface itself = new Interface();
  itself.setComboBoxItems();`

//調用方法setComboBoxItems

這是setComboBoxItems（）方法：

public void setComboBoxItems() {
            ResultSet rset = null;
            Statement stmt = null;
            Connection connect = null;
            try {
                stmt = connect.createStatement();
                rset = stmt.executeQuery( "SELECT * FROM DB_Library.dbo.categories" );
                while( rset.next() ) {
                    String comboItem = rset.getString( "categoryName" );
                    System.out.print( "now combobox items will run!" );
                    categoriesComboBox.addItem( comboItem );
                }
            } catch (SQLException ex) {
                System.out.print("error from set ComboBox: ");
                Logger.getLogger(Interface.class.getName()).log(Level.SEVERE, null, ex);
            }
        }

但它為我返回了我無法解決的錯誤，

Answer 1

因此，您似乎沒有連接：

  Connection connect = null;
   try {
       stmt = connect.createStatement();

這里的連接仍然為空。 是不是