Swing JBotton, JFrame , Jlabel and JTextFiled

TFDemo

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;


public class TFDemo implements ActionListener {
	JTextField jtf;
	JButton jbtnRev;
	JLabel jlabPrompt, jlabContents;
	
	TFDemo() {
		// TODO Auto-generated constructor stub
		JFrame jfrm = new JFrame("Use a Text Field");
		jfrm.setLayout(new FlowLayout());
		jfrm.setSize(240, 120);
		jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		jtf = new JTextField(10);
		jtf.setActionCommand("myTF");
		JButton jbtnRev = new JButton("Reverse");
		
		jtf.addActionListener(this);
		jbtnRev.addActionListener(this);
		
		jlabPrompt = new JLabel("Enter text:");
		jlabContents = new JLabel("");
		
		jfrm.add(jlabPrompt);
		jfrm.add(jtf);
		jfrm.add(jbtnRev);
		jfrm.add(jlabContents);
		
		jfrm.setVisible(true);
		
	}
	public void actionPerformed(ActionEvent ae) {
		if(ae.getActionCommand().equals("Reverse")) {
			String orgStr = jtf.getText();
			String resStr = "";
			
			for(int i = orgStr.length()-1; i>=0; i--) {
				resStr += orgStr.charAt(i);
			}
			jtf.setText(resStr);
		}else
			jlabContents.setText("you passed enter. text is " + jtf.getText());
	}

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		SwingUtilities.invokeLater(new Runnable(){
			public void run() {
				new TFDemo();			
			}
		});

	}

}