Worksheet: J5

Worksheets are self-guided activities that reinforce lectures. They are not graded for accuracy, only for completion. Submit a file called worksheet-J5.md on BB for this assignment.

Note

Attempt to answer these questions before running the code. This will improve your ability to analyize and reason about code without an IDE or compiler. This skill we be helpful on the exams.

Questions

1. How does object-oriented programming pair so closely with GUIs?

2. What is the relationship between WindowListener and WindowAdapter?

3. What does the program below produce for a GUI? (You can sketch and upload an image or describe it – do this without running the program to make sure you understand what each line below is doing).

    // For reference
       /*        N
       *         |
       *      W--|--E
       *         |
       *         S
       */
       public static void main(final String args[]) {
           JFrame frame = new JFrame();
   
           JButton bOne = new JButton("1");
           JButton bTwo = new JButton("2");
           JButton bThree = new JButton("3");
           JButton bFour = new JButton("4");
           JButton bFive = new JButton("5");
           JButton bSix = new JButton("6");
   
           JPanel primes = new JPanel();
           JPanel composites = new JPanel();
   
           primes.setLayout(new BorderLayout());
           composites.setLayout(new BorderLayout());
   
           primes.add(bTwo, BorderLayout.EAST);
           primes.add(bThree,BorderLayout.WEST);
           primes.add(bFive,BorderLayout.NORTH);
   
           composites.add(bFour, BorderLayout.NORTH);
           composites.add(bSix, BorderLayout.CENTER);
    
           frame.add(primes, BorderLayout.WEST);
           frame.add(composites, BorderLayout.EAST);
           frame.add(bOne, BorderLayout.CENTER);
           frame.pack();
           frame.setTitle("Quiz J4-2");
           frame.setSize(400, 400);
           frame.setLocation(100, 100);
           frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
           frame.setVisible(true);
       }
   

4. Modify the HelloGoodbyeEx2 code to update the number of times the button has been clicked on the button’s label itself.

5. Consider the following Java swing GUI

   public class RedPillBluePill extends JFrame {
       JLabel label;
   
       public RedPillBluePill() {
           this.setSize(300, 300);
           this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   
           JPanel panel = new JPanel(new BorderLayout());        
           JButton red = new JButton("red");
           JButton blue = new JButton("blue");
           panel.add(red, BorderLayout.EAST);
           panel.add(blue, BorderLayout.WEST);
           label = new JLabel("click a button");
           this.add(label, BorderLayout.NORTH);
           this.add(panel, BorderLayout.SOUTH);
   
           red.addActionListener(new ActionListener() {
               @Override
               public void actionPerformed(ActionEvent e) {
                   // TODO Auto-generated method stub
                   label.setText("RED");        
               }
           });
   
           blue.addActionListener(new ActionListener() {
   
               @Override
               public void actionPerformed(ActionEvent e) {
                   // TODO Auto-generated method stub
                   label.setText("BLUE");
               }
   
           });
       }
   }
   

   Convert the ActionListeners to Lambda Functions.

6. Explain why for ActionListener you can use a Lambda function but for WindowListener you cannot?

7. Write a program that allows you to enter a 6-digit PIN, like you would on your smartphone to unlock it. It should have the following layout:

   
    [ DISPLAY PIN AS TYPED ]
   
      [ 1 ]  [ 2 ] [ 3 ] 
      
      [ 4 ]  [ 5 ] [ 6 ]    
      
      [ 7 ]  [ 8 ] [ 9 ]       
   
      [ < ]  [ 0 ] 
   
   

   Where [ < ] is a “backspace” button. The display should show the PIN as it is typed, and when the user enters the PIN 202113, the display changes to “YOU MAY ENTER!”