Why are the buttons invisible on WM_CREATE?

Question

Can anybody tell me why the buttons are invisible at Program start? They are only then visible, if the client are is invalidated, in other words, if i resize/minimize the window etc.
public class Calculator extends Frame
     private Button[] button;
     private Panel p_button;
     public Calculator()
          super();
          SetWindowProperties();
          button = new Button[10];
          p_button = new Panel();
          CreateButtons();
          AddPanels();          
          AddButtons();
          SetButtonProperties();          
          addWindowListener(new WindowHandler());
     private void SetWindowProperties()
          setTitle("Calculator");
          setBackground(Color.white);
          setLayout(new BorderLayout());
          setSize(400,400);
          setLocation(250,200);
          setVisible(true);
     private void CreateButtons()
          for (int i=0; i<=9; i++)
               button[i] = new Button(String.valueOf(i));
     private void SetButtonProperties()
          for (int i=0; i<=9; i++)
               button.setSize(50, 50);
               button[i].setBackground(Color.gray);
     private void AddButtons()
          p_button.setLayout(new GridLayout(5, 3, 5, 5));
          for (int i=1; i<=9; i++)
               p_button.add(button[i]);
          for (int i=1; i<=9; i++)
               button[i].addActionListener(new ButtonHandler());
     private void AddPanels()
          add(p_button, BorderLayout.CENTER);

Answer 1

move
SetWindowProperties();
after
SetButtonProperties();
if i do that, i never can see the buttons, and this is obvoius.(your suggestion is not logical)
I am a C++-Programmer and i simply dont like the Java coding convention.
By the way, does anyone have still an idea, why the buttons are not visible at programstart?
What about:
button = new Button(String.valueOf(i));
What do you think of that statement?What should i think of ? It creates buttons with captions 1,2,3 ...
PS: At the end of line i forgot to copy the last end-block statement from the code during posting.
So if anyone tries the code, please add a " } "