Section 4.8 Exercises
Exercises IO Exercises
Fill in the blank.
Fill in the blanks in each of the following sentences:
2.
Java GUIs utilize a form of control known as programming.
3.
When the user clicks on a programโs
JButton
, an will automatically be generated.
4.
Two kinds of objects that generate
ActionEvent
s are and . JButton
s, JTextField
s, and JLabel
s are all subclasses of .
5.
The
JFrame
class is a subclass of .
6.
If a Java class intends to handle
ActionEvent
s, it must implement the interface.
7.
8.
Look up the documentation for the
JButton
class on Oracleโs Web site: https://docs.oracle.com/javase/8/docs/api/javax/swing/JButton.html. List the signatures of all its constructors.
9.
10.
11.
12.
Suppose you have a program containing a
JButton
named button
. Describe what happens, in terms of Javaโs event handling model, when the user clicks the button.
13.
14.
Modify the GUI in the previous exercise so that it contains three
JButton
s, initially labeled โFirst,โ โSecond,โ and โThird.โ Each time the user clicks one of the buttons, the labels on the buttons should be rotated. Second should get firstโs label, third should get secondโs, and first should get thirdโs label.
15.
Design and implement a GUI that contains a
JTextField
and two JButton
s, initially labeled โLeftโ and โRight.โ Each time the user clicks a button, display its label in the JTextField
. A JButton()
โs label can be gotten with the getText()
method.
16.
You can change the size of a
JFrame
by using the setSize(int h, int v)
method, where h and v give its horizontal and vertical dimensions pixels. Write a GUI application that contains two JButton
s, labeled โBigโ and โSmall.โ Whenever the user clicks on small, set the JFrame's
dimensions to 200 ร 100, and whenever the user clicks on big, set the dimensions to 300 ร 200.
17.
Rewrite your solution to the previous exercise so that it uses a single button whose label is toggled appropriately each time it is clicked. Obviously, when the
JButton
is labeled โBig,โ clicking it should give the JFrame
its big dimensions.
18.
Challenge: Design and write a Java GUI application that allows the user to change the
JFrame
โs background color to one of three choices, indicated by buttons. Like all other Java Component
s, JFrame
โs have an associated background color, which can be set by the following commands: setBackground(Color.red);
setBackground(Color.yellow);
The
setBackground()
method is defined in the Component
class, and 13 primary colorsโblack
, blue
, cyan
, darkGray
, gray
, green
, lightGray
, magenta
, orange
, pink
, red
, white
, yellow
โare defined in the java.awt.Color
class.
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