import java.io.Console;
import java.util.Arrays;
import java.io.IOException;

public class Password {
  
  public static void main (String args[]) throws IOException {

    Console c = System.console();
    if (c == null) {
      System.err.println("No console.");
      System.exit(1);
    }

    String login = c.readLine("Enter your login: ");
    char [] oldPassword = c.readPassword("Enter your old password: ");

    if (verify(login, oldPassword)) {
      boolean noMatch;
      do {
        char [] newPassword1 = c.readPassword("Enter your new password: ");
        char [] newPassword2 = c.readPassword("Enter new password again: ");
        noMatch = ! Arrays.equals(newPassword1, newPassword2);
        if (noMatch) {
          c.format("Passwords don't match. Try again.%n");
        } else {
          change(login, newPassword1);
          c.format("Password for %s changed.%n", login);
        }
        Arrays.fill(newPassword1, ' ');
        Arrays.fill(newPassword2, ' ');
      } while (noMatch);
    }

    Arrays.fill(oldPassword, ' ');
  }
  
  // Dummy change method.
  static boolean verify(String login, char[] password) {
    // This method always returns
    // true in this example.
    // Modify this method to verify
    // password according to your rules.
    return true;
  }

  // Dummy change method.
  static void change(String login, char[] password) {
    // Modify this method to change
    // password according to your rules.
  }
}