• Many applications use windows or dialog boxes (also called dialogs) to display output.
• Typically, dialog boxes are windows in which programs display important messages to users.
• Class JOptionPane provides prebuilt dialog boxes that enable programs to display windows containing messages—such windows are called message dialogs

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• Package javax.swing contains many classes that help you create graphical user interfaces (GUIs).
• GUI components facilitate data entry by a program’s user and presentation of outputs to the user.
• JOptionPane method showMessageDialog displays a dialog box containing a message.
  • Requires two arguments.
  • The first helps the Java application determine where to position the dialog box.
    • If the first argument is null, the dialog box is displayed at the center of your screen.
  • The second argument is the String to display in the dialog box.
• JOptionPane method showMessageDialog is a static method.
• Such methods often define frequently used tasks.
• Typically called by using method’s class name followed by a dot (.) and the method name, as in

ClassName.methodName( arguments )

• Notice that you do not create an object of class JOptionPane to use its static method showMessageDialog
• An input- dialog allows the user to enter data into a program.
• JOptionPane method showInputDialog displays an input dialog.
  • Contains a prompt and a field (known as a text field) in which the user can enter text
• Method showInputDialog (line 11) returns a String containing the characters typed by the user
• If you press the dialog’s Cancel button or press the Esc key, the method returns null
• static String method format returns a formatted String.
• Method format works like method System.out.printf, except that format returns the formatted String rather than displaying it in a command window.