import java.awt.*;import java.awt.event.*;import javax.swing.*;import java.io.*;import java.lang.*;// This example demonstrates the use of JButton, JTextField// and JLabel.public class ConvertText implements ActionListener, MouseListener{ JFrame convertTextFrame; JPanel convertTextPanel; JTextField enterString; JLabel enterAString; JButton upper, lower; // Constructor public ConvertText() { // Create the frame and container. convertTextFrame = new JFrame("Convert String"); convertTextPanel = new JPanel(); convertTextPanel.setLayout(new GridLayout(2,2)); // Add the widgets. addWidgets(); // Add the panel to the frame. convertTextFrame.getContentPane().add(convertTextPanel, BorderLayout.CENTER); // Exit when the window is closed. convertTextFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // Show the converter. convertTextFrame.pack(); convertTextFrame.setVisible(true); upper.addMouseListener( this ); lower.addMouseListener(this); } // Create and add the widgets for converter. private void addWidgets() { // Create widgets. enterAString = new JLabel("Enter A String", SwingConstants.LEFT); upper = new JButton("Upper"); enterString = new JTextField(2); lower = new JButton("Lower"); // Listen to events from the buttons. upper.addActionListener(this); lower.addActionListener(this); // Add widgets to container. convertTextPanel.add(enterAString); convertTextPanel.add(upper); convertTextPanel.add(enterString); convertTextPanel.add(lower); enterAString.setBorder(BorderFactory.createEmptyBorder(5,5,5,5)); } // Implementation of ActionListener interface. public void actionPerformed(ActionEvent event) { if (event.getSource() instanceof JButton){ JButton clickedButton = (JButton) event.getSource(); String buttonText = clickedButton.getText(); if (buttonText.equals("Upper")){ for (int i = 0; i < enterString.length; i++) { enterString[i] = Character.toUpperCase(enterString[i]); } } else { for (int i = 0; i < enterString.length; i++) { enterString[i] = Character.toLowerCase(enterString[i]); } } } else {} } public void mouseClicked(MouseEvent e){} public void mouseEntered(MouseEvent e){} public void mouseExited(MouseEvent e){ } public void mouseReleased(MouseEvent e){} public void mousePressed(MouseEvent e){ } // main method public static void main(String[] args) { // Set the look and feel. try { UIManager.setLookAndFeel( UIManager.getCrossPlatformLookAndFeelClassName()); } catch(ClassNotFoundException e){ } catch(InstantiationException e){ } catch(IllegalAccessException e){ } catch(UnsupportedLookAndFeelException e){ } ConvertText convert = new ConvertText(); }}