Prentice.Hall.Introduction.to.Java.Programming,.Brief.Version.9th.(2014).[sharethefiles.com]

The new icons and mnemonics are shown in Figure 38.2(c). You can
also use JMenuItem constructors like the ones that follow to
construct and set an icon or mnemonic in one statement.
public JMenuItem(String label, Icon icon);
public JMenuItem(String label, int mnemonic);
By default, the text is at the right of the icon. Use
setHorizontalTextPosition(SwingConstants.LEFT) to set the text to
the left of the icon.
To select a menu, press the ALT key and the mnemonic key. For
example, press ALT+F to select the File menu, and then press
ALT+O to select the Open menu item. Keyboard mnemonics are
useful, but they only let you select menu items from the
currently open menu. Key accelerators, however, let you select a
menu item directly by pressing the CTRL and accelerator keys. For
example, by using the following code, you can attach the
accelerator key CTRL+O to the Open menu item:
jmiOpen.setAccelerator(KeyStroke.getKeyStroke
(KeyEvent.VK_O, ActionEvent.CTRL_MASK));
The setAccelerator method takes a KeyStroke object. The static
method getKeyStroke in the KeyStroke class creates an instance of
the keystroke. VK_O is a constant representing the O key, and
CTRL_MASK is a constant indicating that the CTRL key is
associated with the keystroke.
NOTE: As shown in Figure 17.1, AbstractButton is the
superclass for JButton and JMenuItem, and JMenuItem is a
superclass for JCheckBoxMenuItem, JMenu, and
JRadioButtonMenuItem. The menu components are very
similar to buttons.
38.2.3 Example: Using Menus
This section gives an example that creates a user interface to
perform arithmetic. The interface contains labels and text fields
for Number 1, Number 2, and Result. The Result text field
displays the result of the arithmetic operation between Number 1
and Number 2. Figure 38.3 contains a sample run of the program.
Figure 38.3
Arithmetic operations can be performed by clicking buttons or by
choosing menu items from the Operation menu.
Here are the major steps in the program (Listing 38.1):
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