java - ArrayList 不会添加超过一项

Question

我正在尝试创建一个 String[] 的 ArrayList，但无法让它添加多个项目。最终我想从 ArrayList 中提取项目并将它们发送到 JTable。该程序有 5 个独立的类，但以下是此问题的适用代码:

    static JComboBox<String> foodChoice;
    DefaultTableModel foodList;
    static String[] newFood;
    static List<String[]> foodData;
    JTextField newFoodText, portionText, carbsText;

public Main() {
        void createFood() {

            String[] foodProperties = new String[3];
            foodProperties[0] = newFoodText.getText();
            foodProperties[1] = portionText.getText();
            foodProperties[2] = carbsText.getText();
            Main.createFood(foodProperties);
            }

    static void createFood(String[] foodArray) {
            foodData = new ArrayList<String[]>();
            foodData.add(foodArray);
            foodChoice.addItem(foodArray[0]);
        }

        void addFoodToTable() {

            String[] s = new String[3];
            s = (String[]) foodData.get(foodChoice.getSelectedIndex());
            System.out.println(foodData.get(0));
            System.out.println(foodData.get(1));       
        }

单击按钮即可调用

addFoodToTable。所以我遇到的问题是(基于系统输出)我将获得指向 ArrayList 中第一个条目的指针地址，但随后出现空指针异常，表明当它尝试打印时它超出了长度 0 的范围第二个要安慰。这显然是在调用 createFood() 3 或四次以填充 foodData 后发生的。如果需要，我可以提供额外的代码，但将其全部放入这篇文章中实在太多了。谢谢!

Answer 1

每次调用 createFood 时都会清除 foodData 删除此行:

foodData = new ArrayList();

并将初始化移至静态级别，如下所示:

static JComboBox<String> foodChoice;
DefaultTableModel foodList;
static String[] newFood;
static List<String[]>  foodData = new ArrayList<String[]>();
JTextField newFoodText, portionText, carbsText;

public Main() {
  void createFood() {

    String[] foodProperties = new String[3];
    foodProperties[0] = newFoodText.getText();
    foodProperties[1] = portionText.getText();
    foodProperties[2] = carbsText.getText();
    Main.createFood(foodProperties);
  }

  static void createFood(String[] foodArray) {
    foodData.add(foodArray);
    foodChoice.addItem(foodArray[0]);
  }

  void addFoodToTable() {

    String[] s = new String[3];
    s = (String[]) foodData.get(foodChoice.getSelectedIndex());
    System.out.println(foodData.get(0));
    System.out.println(foodData.get(1));
  }