import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class SecurityKey extends JPanel
 
  implements ActionListener {
  private static String pass = "Convalida";
 
  private JFrame controllingFrame; 
  private JPasswordField campoPass;
 public SecurityKey(JFrame f) {
  controllingFrame = f;
 campoPass = new JPasswordField(8);
  campoPass.setActionCommand(pass);
  campoPass.addActionListener(this);
 JLabel label = new JLabel("Inserisci la password: ");
  label.setLabelFor(campoPass);
 JComponent buttonPane = createButtonPanel();
 JPanel textPane = new JPanel(new FlowLayout(FlowLayout.TRAILING));
  textPane.add(label);
  textPane.add(campoPass);
 add(textPane);
  add(buttonPane);
  }
 protected JComponent createButtonPanel() {
  JPanel p = new JPanel(new GridLayout(0,1));
  JButton keyButton = new JButton("Ivia");
 
  keyButton.setActionCommand(pass);
  keyButton.addActionListener(this);
 
  p.add(keyButton);
  return p;
  }
 public void actionPerformed(ActionEvent e) {
  String cmd = e.getActionCommand();
 if (pass.equals(cmd)) { 
  char[] input = campoPass.getPassword();
  if (controlloPass(input)) {
  JOptionPane.showMessageDialog(controllingFrame,
"Password corretta.");
  } else {
  JOptionPane.showMessageDialog(controllingFrame,
"Password non valida.",
"Errore",
  JOptionPane.ERROR_MESSAGE);
  }
 for (int j = 0; j < input.length; j++) {
  input[j] = 0;
  }
 campoPass.selectAll();
  resetFocus();
  } 
  }
 private static boolean controlloPass(char[] input) {
  boolean Ctrl = true;
  char[] Password = { 'j', 'a', 'v', 'a' };
 if (input.length != Password.length) {
  Ctrl = false;
  } else {
  for (int j = 0; j < input.length; j++) {
  if (input[j] != Password[j]) {
  Ctrl = false;
  }
  }
  }
 
  for (int j = 0; j < Password.length; j++) {
  Password[j] = 0;
  }
 return Ctrl;
  }
 protected void resetFocus() {
  campoPass.requestFocusInWindow();
  }
 
  private static void interfaccia() {
 
  JFrame frame = new JFrame("SecurityKey");
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
  final SecurityKey newContentPane = new SecurityKey(frame);
  newContentPane.setOpaque(true); 
  frame.setContentPane(newContentPane);
 
  frame.addWindowListener(new WindowAdapter() {
  public void windowActivated(WindowEvent e) {
  newContentPane.resetFocus();
  }
  });
 
  frame.pack();
  frame.setVisible(true);
  }
 public static void main(String[] args) {
 
  javax.swing.SwingUtilities.invokeLater(new Runnable() {
  public void run() {
  interfaccia();
   }
  });
 }
}