(Adding new features into Listing 17.2, ButtonDemo.java, incrementally) Improve Listing...

(Adding new features into Listing 17.2, ButtonDemo.java, incrementally) Improve Listing 17.2 incrementally, as follows (see Figure 17.41):

1. Add a text field labeled "Enter a new message" in the same panel with the buttons. When you type a new message in the text field and press the Enter key, the new message is displayed in the message panel.

2. Add a combo box labeled "Select an interval” in the same panel with the buttons. The combo box enables the user to select a new interval for moving the message. The selection values range from 5 to 100 with interval 5. The user can also type a new interval in the combo box.

3. Add three radio buttons that enable the user to select the foreground color for the message as Red, Green, and Blue. The radio buttons are grouped in a panel, and the panel is placed in the north of the frame's content pane.