java登录小程序出错
Netbeans 6.7.1 ,这是个简单的登录框小程序，输入用户名和密码，正确就提示正确，错误就提示错误然后重置输入框，代码如下：

package Package1;

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



public class LogIn {
public static void main(String agrs[]){
  MainWindow Login=new MainWindow();
  Login.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  Login.setVisible(true);
  Login.setResizable(false);

}
}

class MainWindow extends JFrame {
  JPanel panel;
  FlowLayout layout;
  JLabel label1,label2,label3;
  JButton login;
  JTextField username;
  JPasswordField password;

  public MainWindow(){
  setTitle("Log in");
  setSize(500,500);
  layout=new FlowLayout(FlowLayout.CENTER);
  panel=new JPanel(layout);
   
  login=new JButton("Log in");
  username=new JTextField(10);
  password=new JPasswordField(10);
  password.setEchoChar('*');

  label1=new JLabel("Please input your username and password:");
  label2=new JLabel("username:");
  label3=new JLabel("password:");
   
  panel.add(label1);
  panel.add(label2);
  panel.add(username);
  panel.add(label3);
  panel.add(password);
  panel.add(login);

  this.setContentPane(panel);
   
  login.addMouseListener(new MouseAdapter(){
  public void mouseClicked(MouseEvent e){
  String str1;
  char[] PInput;

  str1=username.getText();
  PInput=password.getPassword();
  if((str1.equals("javaname"))&&(PInput.equals("javapassword")))
  label1.setText("Correct!");
  else{
  username.setText("");
  password.setText("");
  label1.setText("Input again!");
  }

  }

  });
   
   
  }
   
}


我运行始终显示有错误，看不到任何运行结果，不知道哪里有错
另外，怎么控制提示标签和输入框的位置关系？比如我想像QQ那样，变量的位置关系是：
L1:label1
L2:label2,username
L3:label3,password
L4:login

------解决方案--------------------
package jframe.zidong;

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;

public class MyJFrame extends JFrame
{
private JPanel panel1,panel2,panel3;
final private JLabel label1=new JLabel("Please input your username and password:");;
final private JLabel label2=new JLabel("username:");;
final private JLabel label3=new JLabel("password:");
final private JButton login=new JButton("Log in");
final private JTextField username=new JTextField(10);
final private JPasswordField password=new JPasswordField(10);

public MyJFrame(String title)
{
super(title);
setSize(300,200);
setLocation(400, 200);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setJPanel();
setLayout(new GridLayout(3,1));
getContentPane().add(panel1);
getContentPane().add(panel2);
getContentPane().add(panel3);
}
public void setJPanel()
{

panel1=new JPanel();