Check IP

package checkip;

import java.awt.Button;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.net.InetAddress;
import java.net.UnknownHostException;
import javax.swing.JOptionPane;

/**
 *
 * @author Thieu Mao
 */
public class CheckIP extends Frame implements ActionListener, KeyListener {

    private TextField tfInput;
    private Button btEnter;
    private String strAddress;
    private InetAddress[] addresses;

    public static void main(String[] args) {
        CheckIP frame = new CheckIP("Check IP - thieumao");
        frame.pack();
        frame.setVisible(true);
    }

    public CheckIP(String title) {
        super(title);
        this.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent we) {
                System.exit(0);
            }
        });
        tfInput = new TextField(20);
        btEnter = new Button("Enter");
        this.setLayout(new FlowLayout());
        this.add(tfInput);
        this.add(btEnter);
        tfInput.addKeyListener(this);
        btEnter.addActionListener(this);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == btEnter) {
            strAddress = tfInput.getText();
            try {
                addresses = InetAddress.getAllByName(strAddress);
            } catch (UnknownHostException ex) {
                System.err.println("Cound not find " + strAddress);
            }
            if (addresses == null) {
                JOptionPane.showMessageDialog(null, "Cound not find " + strAddress);
            } else {
                JOptionPane.showMessageDialog(null, addresses);
            }
            tfInput.requestFocus();
        }
    }

    @Override
    public void keyTyped(KeyEvent e) {
    }

    @Override
    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode() == e.VK_ENTER) {
            strAddress = tfInput.getText();
            try {
                addresses = InetAddress.getAllByName(strAddress);
            } catch (UnknownHostException ex) {
                System.err.println("Cound not find " + strAddress);
            }
            if (addresses == null) {
                JOptionPane.showMessageDialog(null, "Cound not find " + strAddress);
            } else {
                JOptionPane.showMessageDialog(null, addresses);
            }
        }
        if (e.getKeyCode() == e.VK_ESCAPE) {
            System.exit(0);
        }
    }

    @Override
    public void keyReleased(KeyEvent e) {
    }
}