import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class OOP_Exer3 implements ActionListener
{
public static void main(String [] args)
{
FlowLayout fl = new FlowLayout();
//create the frame
JFrame fr = new JFrame("OOP Exercise 3");
//set frame size
fr.setSize(400,200);
//create labels
JLabel lbl1 = new JLabel("Enter your name: ");
JLabel lbl2 = new JLabel();
//create text field
JTextField txt1 = new JTextField(25);
//create button
JButton btn1 = new JButton("Greet Me");
//add components to the frame
fr.setLayout(fl);
fr.add(lbl1);
fr.add(txt1);
fr.add(btn1);
fr.add(lbl2);
btn1.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent ae)
{
if(txt1.getText().equals(""))
{
JOptionPane.showMessageDialog(null,"Enter Your Name",
"Error", JOptionPane.ERROR_MESSAGE);
txt1.requestFocusInWindow();
}
else
{
String myName = txt1.getText();
lbl2.setText("Hi!, " + myName + ".");
