Exercise 23's Window is useless, even compared to Squarer (in Exercise 1) - it doesn't even take a number in and square it. We can do that by using some standard dialogue boxes for text input and message display. Class javax.swing.JOptionPane has many standard dialogues, eg
showMessageDialog ()with single OK buttonshowConfirmDialog ()can have Yes, No, Cancel, etc buttonsshowInputDialog ()prompts for input and user types in or selects from a drop-down list
There are several constants of the form JOptionPane.xxx_OPTION where xxx can be CANCEL, OK, OK_CANCEL, YES_NO, etc
Those calls need parameters of course. Some examples follow.
Message dialogue
JOptionPane.showMessageDialog (w, "message");
w is the parent window, in the sense of the windowing system (not superclass).
Confirmation dialogue
int response = JOptionPane.showConfirmDialog (w,
new String [] { "line 1", "line 2"},
"title", JOptionPane.YES_NO_OPTION,
JOptionPane.WARNING_MESSAGE); // icon kind
switch (response)
{
case JOptionPane.YES_OPTION: yesAction (); break;
case JOptionPane.NO_OPTION: noAction (); break;
case JOptionPane.CLOSED_OPTION:; // leave unchanged
}
Input dialogues
String response = JOptionPane.showInputDialog (w, "Enter x:");
String response = (String) JOptionPane.showInputDialog (
w, // Parent window
"Destination?", // Prompt
"Select destination", // Title
JOptionPane.QUESTION_MESSAGE, // Icon kind
null, // No icon file
new String [] // Choices
{ "Heathrow", "Gatwick", "Stansted" },
"Heathrow"); // Default choice
NB: There are many different overloaded versions of the common dialogue methods - see the API documentation.