小编Cov*_*yro的帖子

我正在尝试格式化一些c#输出,以便一个数字总是有2位数,例如,如果int = 0我想Console.WriteLine(int);生成00.

当我点击时,我在*行之间的行处不断获得空指针异常.我一直在看它大约一个小时,似乎无法找出原因.任何帮助将不胜感激.谢谢.

    private Color currentColor;
    private char currentChar;
    private Letter letter;
    private JComboBox comboBox;
    private JPanel controlPanel;
    private Color[] colorArray = {Color.black,Color.blue,Color.cyan,Color.orange,Color.white,Color.yellow};
    private String[] colorStringArray = {"black","blue","cyan","orange","white","yellow"};
    private ArrayList<Letter> letterList;
    private JButton button1;
    private Canvas canvas;
    public WholePanel()
    {
        comboBox = new JComboBox(colorStringArray);
        // here we use black to draw a letter
        currentColor = colorArray[Color.black];

        // set the default character to 'A'
        currentChar = 'A';

        button1 = new JButton("Undo");


        controlPanel = new JPanel();
        controlPanel.add(button1);
        controlPanel.add(comboBox);

        canvas = new Canvas();
        JSplitPane sp …