JComboBox实现当前所选项功能和JFrame窗口释放资源的dispose()方法

JComboBox有一个

SelectedItem属性，所以使用getSelectedItem()就可以得到当前选中值.

 package ltb20180106;

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

 public class UserLoginApp {

     private JFrame jf;
     private JLabel name;
     private JLabel user;
     private JLabel password;
     private JButton confirm;
     private JButton cancel;
     private JButton quit;

     private JPanel p1;
     private JPanel p2;
     private JpanelAction p3;
     private JPanel p4;

     private JComboBox <String> juser;
     private JTextField jname;
     private JPasswordField jpassword;

     private String[] s= {"学生用户","教师用户"};

     private String ss;
     private char[] c;
     private String bname;
     private String item;

     public UserLoginApp() {

         try {

             jf=new JFrame("用户登录");
             jf.setSize(250, 160);
             jf.setLayout(new BorderLayout());

             name=new JLabel("名字:");
             password=new JLabel("密码:");
             user=new JLabel("用户类型");

             juser=new JComboBox<String>(s);
             jname=new JTextField();
             jpassword=new JPasswordField(); 

             confirm=new JButton("确定");
             cancel=new JButton("取消");
             quit=new JButton("退出");

             p1=new JPanel();
             p1.setLayout(new BoxLayout(p1,BoxLayout.Y_AXIS));//允许垂直或水平布置多个组件的布局管理器
             p1.add(user);
             p1.add(name);
             p1.add(password);
             p1.setSize(100,100);

             p2=new JPanel();
             p2.setLayout(new BoxLayout(p2,BoxLayout.Y_AXIS));
             p2.add(juser);
             p2.add(jname);
             p2.add(jpassword);
             p2.setSize(150,100);

             p3=new JpanelAction();
             p3.setLayout(new FlowLayout());
             p3.add(confirm);
             p3.add(cancel);
             p3.add(quit);
             confirm.addActionListener(p3);
             cancel.addActionListener(p3);
             quit.addActionListener(p3);

             p4=new JPanel();
             p4.setLayout(new FlowLayout());
             p4.add(p1);
             p4.add(p2);

             jf.add(p4,BorderLayout.NORTH);
             jf.add(p3,BorderLayout.CENTER);

             jf.setVisible(true);
             jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
             jf.setLocationRelativeTo(null);

         }catch(Exception e) {

             System.out.println(e.getMessage());

         }

     }

     @SuppressWarnings("serial")
     class JpanelAction extends JPanel  implements ActionListener   {

         public void actionPerformed(ActionEvent e)
         {

              bname=e.getActionCommand();//关键的地方

             if(bname.equals("确定")) {

                 ss=jname.getText();
                 c=jpassword.getPassword();
                 item=(String)juser.getSelectedItem();// JComboBox 当前所选项

                 if(ss.equals("")) {

                     name.setText("用户名不能为空");

                 } else if(c.length==0) {  

                     password.setText("密码不能为空");

                 }else if(item.equals("学生用户")) {

                     if(ss.equals("s")&&new String(c).equals("s")) {//密码字符转化字符串处理

                         name.setText("登录成功");
                         password.setText("登录成功");
                     }
                     System.out.println("学生");

                 }else if(item.equals("教师用户")) {

                     if(ss.equals("t")&&new String(c).equals("t")) {//密码字符转化字符串处理

                         name.setText("登录成功");
                         password.setText("登录成功");

                     }

                     System.out.println("教师");
                 }

             }else if (bname.equals("取消")) {

                 jname.setText("");
                 jpassword.setText("");

             }else if(bname.equals("退出")){

                 jf.dispose();//释放由此 Window、其子组件及其拥有的所有子组件所使用的所有本机屏幕资源。
             }
         }

     }

     public static void main(String[] args) {

           new UserLoginApp();
     }

 }