Simple Java program that demonstrate the JTextField, JButton, JFrame and JLabel!

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// Use a text field.

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

class TFDemo implements ActionListener {
 JTextField jtf;
 JButton jbtnRev;
 JLabel jlabPrompt, jlabContents;

 TFDemo() {
  
  // Create a new JFrame container.
  JFrame jfrm = new JFrame("Use a Text Field");

  // Specify FlowLayout for the layout manager. 
  jfrm.setLayout(new FlowLayout());

  // Give the frame an initial size.
  jfrm.setSize(260, 140);

  // Terminate the program when the user closes the application.
  jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

  // Create a text field
  jtf = new JTextField(10);

  // set the action cmmand for the text field.
  jtf.setActionCommand("myTF");

  // create the reverse button
  JButton jbtnRev = new JButton("Reverse");
 
  // add action listeners.
  jtf.addActionListener(this);
  jbtnRev.addActionListener(this);

  // create the labels.
  jlabPrompt = new JLabel("Enter text: ");
  jlabContents = new JLabel("");

  // add the components to the content pane.
  jfrm.add(jlabPrompt);
  jfrm.add(jtf);
  jfrm.add(jbtnRev);
  jfrm.add(jlabContents);

  // Display tht frame
  jfrm.setVisible(true);  
 }

 // Handle action events.
 public void actionPerformed(ActionEvent ae) {
  
  if(ae.getActionCommand().equals("Reverse")) {
   // The reverse button was pressed.
   String orgStr = jtf.getText();
   String resStr = "";

   // reverse the string in the text field.
   for (int i=orgStr.length()-1; i >= 0; i--)
    resStr += orgStr.charAt(i);

   // store the reversed string in the text field.
   jtf.setText(resStr);
  } else
   // enter was pressed while focus was in the 
   // text field.
   jlabContents.setText("You pressed ENTER. text is: " + jtf.getText());
 }

 public static void main (String args[]) {
  // create the frame on the event dispatching thread.
  SwingUtilities.invokeLater(new Runnable() {
   public void run() {
    new TFDemo ();
   }
  });
 }
}