import javax.swing.*;

// A privileged aspect has access to the privite fields of any class,
// yes, that's right.  No reflection and no hypocrisy.
privileged aspect secureGPA // securely change the GPA with a password
{
    public void student.changeGPA(double gpa)
    { this.gpa = gpa; }

    private String student.password;  // private within aspect, not student

    static String randomstring()  // utility to generate random password
    {
	int n = (int)(Math.random()*5)+4;  // random password length;
	String s = "";
	for(;n>0;n--) s+=(char)( (int)(Math.random()*26)+97 ); //lower case
	return s;
    }

    // with advice you can change main without changing main...
    after(student s): execution(public student.new(..)) && target(s)
	{
	    s.password = randomstring();  // generate random password
	    JOptionPane.showMessageDialog(null,
		 s.name+", Your password is "+s.password);
	}

    before(student s): call(void student.changeGPA(double)) && target(s)
    {
      String pswd = JOptionPane.showInputDialog(null,
		 s.name+", Enter password to change your gpa: ");
      if (!s.password.equals(pswd))
       throw new RuntimeException("Wrong password. Beware of motherhackers!");
    }
}//secureGPA

// currently extendstudent advice has precedence over extendinterface
aspect reorderaspects
{
    declare precedence: secureGPA, *; // precedence over all other aspects
}