JAVA新手 初级的问题 求助

我写的程序 谁知道错误在哪里 急啊
就是连BUTTON都出不来

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class MiniMineSweeper extends JFrame
{
static int a = (int) Math.floor(Math.random()*9);
JButton[] jbt= new JButton[9];

public void Welcome()
{

JOptionPane.showMessageDialog(null,"Welcome to Mini-MineSweeper!\nThe object of the game is to click on all\n the squares EXCEPT the one with the bomb.\n(There is only one bomb).To choose a square\n to display please simply click on the square.","Message",JOptionPane.INFORMATION_MESSAGE);
}

public MiniMineSweeper()
{
Container container =getContentPane();
container.setLayout(new GridLayout(3,3,0,0));

for (int i=1;i<=9;i++)
{
jbt[i]= new JButton();
jbt[i].setBackground(Color.gray);
container.add(jbt[i]);
container.valid

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