import javax.swing.*;
import java.awt.event.*;
import java.awt.*;

public class Fonts2 
{  
    public static void main(String[] args) 
    {
	SwingApp app = new SwingApp(300, 200);	    // set app window size
	app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    }
}

class SwingApp extends JFrame implements ActionListener
{
    private int fontNumber = 0;
    private final DrawPanel panel;		    // class variable
    private final String[] availFonts;
    private final JLabel jl0, jl1, jl2, jl3;
    private final JButton jb1, jb2;

    public SwingApp(int width, int height)	    // class constructor
    {
	super();				    // call to super class constructor
	Container pane = super.getContentPane();    // create layout, set colors
	panel = new DrawPanel();		    // add GUI components
	panel.setBackground(Color.yellow);
	panel.setLayout(new GridLayout(5,1));
	
	GraphicsEnvironment gg=GraphicsEnvironment.getLocalGraphicsEnvironment();
	availFonts = gg.getAvailableFontFamilyNames();
	jl0 = new JLabel("Total number of fonts: " + availFonts.length,
                        SwingConstants.CENTER);
	for (int i=0; i<availFonts.length; i++)
	    System.out.println(availFonts[i]);
	jl1 = new JLabel("", SwingConstants.CENTER);
	jl1.setFont(new Font("Monospaced", Font.PLAIN, 16));
	jl2 = new JLabel("", SwingConstants.CENTER);
	jl3 = new JLabel("", SwingConstants.CENTER);
	setLabels(0);
	
	panel.add(jl0);
	panel.add(jl1);
	panel.add(jl3);
	panel.add(jl2);

	JPanel jp = new JPanel();
	jp.setLayout(new GridLayout(1,2));
	jb1 = new JButton("Prev font");
	jb2 = new JButton("Next font");
	jp.add(jb1);
	jp.add(jb2);
	panel.add(jp);

	jb1.addActionListener(this);
	jb2.addActionListener(this);
	pane.add(panel);
	
	Toolkit toolkit = Toolkit.getDefaultToolkit();	// optionally position JFrame
	Dimension screenSize = toolkit.getScreenSize(); // in the middle of the screen 
	super.setLocation((screenSize.width - width)/2, (screenSize.height - height)/2);	
	super.setTitle("Swing app");		    // set desired window title
	super.setSize(width, height);		    // set desired window size
	super.setVisible(true);	
	// add here more code for GUI components
    }

    @Override
    public void actionPerformed(ActionEvent e)
    {
	if (e.getSource() == jb1)
	{
	    fontNumber--;
	    if (fontNumber < 0)
		fontNumber = availFonts.length + fontNumber;
	}
	else if (e.getSource() == jb2)
	    fontNumber = (fontNumber + 1) % availFonts.length;
	setLabels(fontNumber);
	panel.repaint();
   }
    
    public final void setLabels(int n)
    {
	jl1.setText((n+1) + ": \"" + availFonts[n] + "\"");
	jl2.setText(availFonts[n]);
	Font font = new Font(availFonts[n], Font.PLAIN, 24);
	jl2.setFont(new Font(availFonts[n], Font.PLAIN, 24));
	FontMetrics fm = panel.getFontMetrics(font);
	jl3.setText("(l, a, d, h) = (" + fm.getLeading() + ", "
                                    + fm.getAscent() + ", "
                                    + fm.getDescent() + ", "
                                    + fm.getHeight() + ")");
   }
}

class DrawPanel extends JPanel			    // main window panel
{
    @Override
    public void paintComponent(Graphics g)
    {
	super.paintComponent(g);		    // must be the 1st line
	// add here more code for drawing on panel 
    }
}