// java public class DonorGUI extends JFrame { public static final String ELIGIBLE = "Eligible!"; public static final String NOT_ELIGIBLE = "Sorry, not eligible."; public static final String INPUT_ERROR = "Error - enter positive numbers"; private JPanel rootPanel; private JButton checkEligibilityButton; private JTextField weightTextField; private JTextField ageTextField; private JLabel resultLabel; DonorGUI() { this.setContentPane(rootPanel); pack(); setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE); setVisible(true); // TODO add a listener for the checkEligibilityButton  // This should verify that the user has entered a positive number  // in both the weightTextField and ageTextField JTextField  // If either or both are not valid, the resultLable should  // display the INPUT_ERROR text.   // If both weight and age are positive numbers, use the data  // to decide if the user is eligible to be a blood donor.  // To be eligible, a person must be 17 or older,  // AND weigh 110 lbs or more.   // Display the ELIGIBLE text if they are eligible.  // Display the NOT_ELIGIBLE text if they are not eligible.   } }