Thread: How to make a class be static if it's the main class.

I've found that it's okay to have an inner class be static but it throws a fit when I try to make the main class static.

I was aiming to make sure that only one instance could be shown at a time.

If I make all the methods static, will that do it? I don't think making it final will do much more than make it sterile( unable to have children).

I'm trying to make a FontChooser.

Also, my ExamplePanel isn't being added right now. Is it because all of my stuff is static?

   import java.awt.event.*;
   import java.awt.*;
   import java.util.*;
   import javax.swing.event.*;
   import javax.swing.*;
   import java.io.*;
 
   public class JFontChooser extends JFrame
   {
 
 
      private Vector<Font> fonts;
      private Vector<String> fontFamilies;
      private Vector<String> fontNames;
      private JList fontList;
      private JScrollPane fontListScroll;
      private JPanel contentPane;
      private JComboBox sizes;
      private Vector<Integer> sizes2;
      private ExamplePanel example;
 
      private class ExamplePanel extends JPanel
      {
 
         private Font f;
         public ExamplePanel(Font f)
         {
            setVisible(true);
            setFont2(f);
            setBackground(Color.WHITE);
         }
 
         public void setFont2(Font f)
         {
            this.f = f;
         }
 
         public Font getFont2()
         {
            return f;
         }
 
 
 
 
         protected void paintComponent(Graphics g)
         {
            String exampleText = "Sample text.";
            g.setFont(getFont2());
            g.drawString(exampleText, 50, 50);
 
 
         }
 
      }
 
      public static Font[] getAllFonts()
      {
         GraphicsEnvironment local = GraphicsEnvironment.getLocalGraphicsEnvironment();
      // get all fonts
         Font[] fonts = local.getAllFonts();
         return fonts;
      }
 
      public static String[] getFontFamilies()
      {
         GraphicsEnvironment local = GraphicsEnvironment.getLocalGraphicsEnvironment();
 
      // get all available font families
         String[] fontFamilies = local.getAvailableFontFamilyNames();
         return fontFamilies;
      }
 
      public  JFontChooser()
      {
         fonts = new Vector<Font>();
         sizes2 = new Vector<Integer>();
         sizes2.add(6);
         sizes2.add(7);
         sizes2.add(8);
         sizes2.add(10);
         sizes2.add(12);
         sizes2.add(14);
         sizes2.add(16);
         sizes2.add(18);
         sizes2.add(20);
         sizes2.add(22);
         sizes2.add(24);
         sizes2.add(36);
         sizes2.add(48);
         sizes2.add(60);
         sizes2.add(72);
 
         sizes = new JComboBox(sizes2);
 
 
         for (int i =0; i < getAllFonts().length; i++)
         {
            fonts.add(getAllFonts()[i]);
 
         }
 
         fontNames = new Vector<String>();
         for (int i = 0; i < fonts.size(); i++)
         {
            fontNames.add(fonts.get(i).getName());
         }
 
         fontList = new JList(fontNames);
         fontListScroll = new JScrollPane(fontList, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
         contentPane = new JPanel();
         contentPane.add(fontListScroll);
         contentPane.add(sizes);
 
         setVisible(true);
         example = new ExamplePanel(new Font("Times New Roman", Font.BOLD, 12));
 
         contentPane.add(example);
 
         setContentPane(contentPane);
 
      }
 
      public static void main(String[] args)
      {
         new JFontChooser();
      }
 
 
 
 
   }

I can get it to come up by setting the example to be the contentPane instead but it won't show the first part and it won't set the background to white like I told it to.

I was aiming to make sure that only one instance could be shown at a time.

Look at the Singleton Pattern

Originally Posted by Norm

Look at the Singleton Pattern

What's a Singleton Pattern? I've heard that phrase before.

try google

Try it and see what happens.

It's unfortunate that swing does not have a built in Font chooser dialog. This class is easy to use should do everything you need.

Is there any way to get Java to accept Windings 1, 2, and 3, Webdings, Symbol, and fonts like that? Right now they're registering as little rectangles for every character when I try those.

Originally Posted by javapenguin

Is there any way to get Java to accept Windings 1, 2, and 3, Webdings, Symbol, and fonts like that? Right now they're registering as little rectangles for every character when I try those.

Sorry I can't help you with that one. Out of interest - why? The only use I have ever found for those symbolic fonts is practical jokes (swapping windings with arial on my colleagues machine and watching the chaos unfold).

Mainly just because if anybody wanted to make a Notepad program that included those, like the Windows Notepad does, and they used Java, they'd have a slight problem it seems.

I have a question, when you make something a Singleton, how would you make sure that that particular calling application can only have one instance yet also ensure that more than one instance for ALL applications is possible? (i.e. Not allow a notepad program to call more than one font selector but allow two separate notepad instances to each have a single font selector running at the same time.

If the notepad instances are in separate JVMs there isn't a problem: they would each use the singleton instance of their own JVM.

On the other hand the notepad instances might all be running in the same JVM. In that case if the font selector is able to support multiple instances why should it care how many instances of it are created and by whom? I guess the font selector could expose a factory method that keeps track of the notepad instances that call it, but why bother? (and the notepad instances could be sneaky and share one another's font selector anyway.) More straight forward, if the notepad instances are concerned that they use a single font selector for all of their windows then they should have a single font selector instance variable and just use it whenever it is needed.

I meant that if one Notepad is running a font selector and I have designed the font selector to be a singleton, what happens if I open another notepad and that notepad tries to create a separate font selector instance?

A.) It won't let it since there is already one being used by the first notepad and only 1 is allowed.
B.) It will allow it provided it doesn't try to open another font selector with that same notepad application
C.) It will take over the font selector from the previous notepad that called it.
D.) None of the above

Try it and find out. I suspect 'D' - both will have their own singleton font selector since they are separate processes.

Speaking of separate processes - this is the third question you have asked on this thread. Why don't you mark it as 'solved' and start a new thread for new questions. It's unlikely you will get answers on singleton design patterns and font selection on a thread titled 'How to make a class static'.