Writing applications instead of applets so our programs are allowed to manipulate files

Writing applications instead of applets so our programs are allowed to manipulate files

Applets that are run via a Web page are restricted in the kinds of actions they can take. In particular, applets are not allowed to read or write files. To work with files we need to write applications instead. There are only a few things we need to do differently:

• We do not extend any of WindowController, Controller, or JApplet. It is not necessary to extend anything.
• The main class (generally the one that creates the GUI) needs a method declared as:

  public static void main (String[] args)
  

  This method should just construct an instance of the class it is in.
• The code that you put in the begin method of your controller or the init method of an applet should be placed in the constructor.
• The constructor needs to create a window to put the GUI components in since there is no Web page to put them in:

  JFrame window = new JFrame();
  

• You add the GUI components to this window's content pane:

  Container contentPane = window.getContentPane();
  

• After you have added all the components, you call pack() to have Java set the window to the right size. (There is no need to set size parameters in Eclipse's Run dialog box.) You then call setVisible(true) to display the window.

Here are the relevant parts of the ShortWordsFixedFiles demo showing how to create an application.

public void createGUI() {
   JFrame frame = new JFrame();
   Container contentPane = frame.getContentPane();

   // Code to create the components is omitted

   frame.pack();
   frame.setVisible(true);
}

public static void main(String[] args) {
   new ShortWordsFixedFiles();
}

Writing applications instead of applets so our programs are allowed to manipulate files