效果图：

字符串大小写转换

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