Java How to Program, Early Objects, 11th Edition

... colors = { "Blue", "Yellow", "Red" };
27 
28            ButtonGroup colorGroup = new ButtonGroup(); // manages color items
29            popupMenu = new JPopupMenu(); // create pop-up menu
30            items = new JRadioButtonMenuItem[colors.length];
31 
32            // construct menu item, add to pop-up menu, enable event handling
33            for (int count = 0 ; count < items.length; count++)
34            {
35               items[count] = new JRadioButtonMenuItem(colors[count]);
36               popupMenu.add(items[count]); // add item to pop-up menu
37               colorGroup.add(items[count]); // add item to button group
38               items[count].addActionListener(handler); // add handler
39            }
40 
41            setBackground(Color.WHITE);
42 
43            // declare a MouseListener for the window to display pop-up menu
44            addMouseListener(
45               new MouseAdapter() ...