package sfms;import java.awt.*;import javax.swing.*;import java.awt.event.*;public class mainWindow extends JFrame implements ActionListener{JButton findSt,addSt,delSt,updateSt,exitB;  public static void main (String args[]){    mainWindow frame=new mainWindow();  }//constructor  public mainWindow(){      Container c=this.getContentPane();    c.setLayout(new GridLayout(2,1));    JPanel lowerPanel=new JPanel();//create label    Font defaultFont=c.getFont();    JLabel label=new JLabel("歡迎進入資料檔案管理系統");    label.setForeground(Color.blue);    label.setFont(new Font("plain",Font.PLAIN,36));    c.add(label);//create Buttons for bottom panel    findSt=new JButton("查詢");    addSt=new JButton("添加");    delSt=new JButton("刪除");    updateSt=new JButton("更新");    exitB=new JButton("退出");//add buttons    lowerPanel.add(findSt);    lowerPanel.add(addSt);    lowerPanel.add(delSt);    lowerPanel.add(updateSt);    lowerPanel.add(exitB);    c.add(lowerPanel);//register frame as listener for button events    findSt.addActionListener(this);    addSt.addActionListener(this);    delSt.addActionListener(this);    updateSt.addActionListener(this);    exitB.addActionListener(this);    this.setSize(400,300);    this.setTitle("SFMS歡迎您");    this .setVisible(true);//create anonymous inner class to handle window closing event    this.addWindowListener(new WindowAdapter(){      public void windoeClosing(WindowEvent event){        shutdown();  }});    }//actionPerformed is involked when a button is clicked    public void actionPerformed(ActionEvent e){      if(e.getSource()==findSt){        findS();      }      if(e.getSource()==addSt){        addS();      }      if(e.getSource()==delSt){        delS();      }      if(e.getSource()==updateSt){        updateS();      }      if(e.getSource()==exitB){        shutdown();      }    }    private void findS(){    }    private void addS(){      AddFI addFi=new AddFI();      addFi.setVisible(true);      this.setVisible(false);    }    private void delS(){    }    private void updateS(){     }    private void shutdown(){    System.exit(0);     }    }