package Chapter1;import java.io.*;import javax.swing.*;import java.awt.*;import java.awt.event.*;import java.sql.*;import java.awt.Rectangle;import java.awt.Font;public class Instructions extends JFrame implements ActionListener{  public static final int WIDTH=400;  public static final int HEIGHT=400;  JLabel jLabel1 = new JLabel();  JButton jButton1 = new JButton();  public Instructions()  {    setSize(WIDTH,HEIGHT);    setTitle("使用說明");    Container contentPane=getContentPane();    contentPane.setBackground(Color.green);    try {      jbInit();    }    catch(Exception e) {      e.printStackTrace();    }  }  public void actionPerformed(ActionEvent e)  {     if  (e.getActionCommand().equals("返回"))     {           this.dispose();           ManagerInterface n1= new ManagerInterface();           StudentInterface n2=new  StudentInterface();           if(Login.jComboBox1.getSelectedIndex()==0)                 {  n1.setVisible(true);  n2.dispose();}           else if(Login.jComboBox1.getSelectedIndex()==1)                 {  n2.setVisible(true);  n1.dispose(); }     }  }  public static void main(String[] args)  {      Instructions n=new Instructions();      n.setVisible(true);  }  private void jbInit() throws Exception {    jLabel1.setFont(new java.awt.Font("Dialog", 1, 13));    jLabel1.setRequestFocusEnabled(true);    jLabel1.setText("此系統用于管理學生信息,包括學生信息的輸入和查詢等功能!");    jLabel1.setBounds(new Rectangle(8, 56, 376, 152));    this.getContentPane().setLayout(null);    jButton1.setBounds(new Rectangle(169, 242, 73, 25));    jButton1.setFont(new java.awt.Font("Dialog", 1, 13));    jButton1.setText("返回");    this.getContentPane().add(jLabel1, null);    this.getContentPane().add(jButton1, null);    jButton1.addActionListener(this);  }}