Java Reference
In-Depth Information
String message = String.format("Total:%5.2f",
total);
sets the
message
variable to the string
ÐTotal: 3.50Ñ
.
A
DVANCED
T
OPIC
4.7: Using Dialog Boxes for Input and
Output
Most program users find the console window rather old-fashioned. The easiest
alternative is to create a separate pop-up window for each input (see An Input
Dialog Box).
Call the static
showInputDialog
method of the
JOptionPane
class, and
supply the string that prompts the input from the user. For example,
String input = JOptionPane.showInputDialog("Enter
price:");
That method returns a
String
object. Of course, often you need the input as a
number. Use the
Integer.parseInt
and
Double.parseDouble
methods
to convert the string to a number:
double price = Double.parseDouble(input);
You can also display output in a dialog box:
JOptionPane.showMessageDialog(null, "Price: " +
price);
Finally, whenever you call the
showInputDialog
or
showMessageDialog
method in a program that does not show any other frame windows, you need to
add a line
System.exit(0);
to the end of your
main
method. The
showInputDialog
method starts a user
interface thread to handle user input. When the
main
method reaches the end, that
thread is still running, and your program won't exit automatically. To force the
program to exit, you need to call the exit method of the
System
class. The
parameter of the exit method is the status code of the program. A code of
0
