效果图：

193123146.jpg

详细代码：

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package  com.lixiyu;
import  java.awt.EventQueue;
import  java.awt.event.ActionEvent;
import  java.awt.event.ActionListener;
import  javax.swing.ButtonGroup;
import  javax.swing.JButton;
import  javax.swing.JFrame;
import  javax.swing.JRadioButton;
import  javax.swing.JTextField;
import  javax.swing.UIManager;
public  class  StringConvert  extends  JFrame {
     private  static  final  long  serialVersionUID = 4556387791998133270L;
     private  JTextField inputTextField;
     private  JTextField outputTextField;
     private  final  ButtonGroup buttonGroup= new  ButtonGroup();
       
     public  static  void  main(String[] args){
         try {
         UIManager.setLookAndFeel( "com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel" );
     } catch (Throwable e){
         e.printStackTrace();
     }
     EventQueue.invokeLater( new  Runnable(){
         public  void  run(){
             try {
                 StringConvert frame= new  StringConvert();
                 frame.setVisible( true );
             } catch (Exception e){
                 e.printStackTrace();
             }
         }
     });
}
//CREATE THE FRAME
public  StringConvert(){
     setTitle( "\u5B57\u7B26\u4E32\u5927\u5C0F\u5199\u8F6C\u6362" );
     setBounds( 100 , 100 , 450 , 214 );
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     getContentPane().setLayout( null );
       
     inputTextField= new  JTextField();
     inputTextField.setBounds( 23 ,  21 ,  383 ,  31 ); //设置输入框位置
     getContentPane().add(inputTextField);
     inputTextField.setColumns( 10 );
       
     JButton button= new  JButton( "\u8F6C\u6362" );
     button.addActionListener( new  ActionListener(){
     public  void  actionPerformed(ActionEvent arg0){
         do_button_actionPerformed(arg0);
     }
     });
     button.setBounds( 23 , 77 , 93 , 23 );
     getContentPane().add(button);
       JRadioButton radioButton =  new  JRadioButton( "大写" );
       radioButton.setActionCommand( "大写" );
       radioButton.setSelected( true );
       radioButton.setBounds( 169 ,  77 ,  76 ,  23 );
       buttonGroup.add(radioButton);
       getContentPane().add(radioButton);
         
       JRadioButton radioButton_1 =  new  JRadioButton( "小写" );
       radioButton_1.setBounds( 280 ,  77 ,  121 ,  23 );
       radioButton_1.setActionCommand( "小写" );
       buttonGroup.add(radioButton_1);
       getContentPane().add(radioButton_1);
         
       outputTextField =  new  JTextField();
       outputTextField.setEditable( false );
       outputTextField.setColumns( 10 );
       outputTextField.setBounds( 23 ,  122 ,  383 ,  31 );
       getContentPane().add(outputTextField);
       @SuppressWarnings ( "unused" )
       String strBook =  "MingRiBook" .toLowerCase();
   }
protected  void  do_button_actionPerformed(ActionEvent arg0){
     String command = buttonGroup.getSelection().getActionCommand(); //获取大小写单选项的选择
boolean  upper=command.equals( "大写" ); //判断是否选择”大写“单选项
String text=inputTextField.getText(); //获取输入字符
if  (upper) { // 大写转换
     outputTextField.setText(text.toUpperCase());
}  else  { // 小写转换
     outputTextField.setText(text.toLowerCase());
}
}
}

本文转自lixiyu 51CTO博客，原文链接：http://blog.51cto.com/lixiyu/1305498，如需转载请自行联系原作者