UTILISATION D'UN JDESKTOPPANE

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

class Quitter implements ActionListener
{
	public void actionPerformed(ActionEvent e)
	{
		System.exit(0);
	}
}

class Nouveau implements ActionListener
{
	public void actionPerformed(ActionEvent e)
	{	
		
		
		i++;
		FenetreSecondaire f = new FenetreSecondaire("Fenetre " + i);
		f.setLocation(x++,y++);
		FenetreConteneur.getInstance().add(f);
		
	}
	
	private int i = 0;
	private int x = 15;
	private int y = 30;
}


class barre extends JMenuBar
{
	public barre()
	{
	
		
	JMenuItem smnu1=new JMenuItem();
	JMenuItem smnu2=new JMenuItem();
	
	JMenu mnu1 = new JMenu();
	
		
	mnu1.setText("Fichier");
	smnu2.setText("Nouveau");
	smnu1.setText("Quitter");
	
	
	
	smnu1.addActionListener(new Quitter());
	smnu2.addActionListener(new Nouveau());
		
	mnu1.add(smnu1);	
	mnu1.add(smnu2);
		
	this.add(mnu1);
	
	this.setVisible(true);
	
	}
	
	
	
}


class FenetreConteneur extends JDesktopPane
{
	private FenetreConteneur()
	{
		int i=0;
		this.add(new FenetreSecondaire("Fenetre " + i));
		this.setVisible(true);
	}
	
	public static FenetreConteneur getInstance()
	{ 
		if(instance == null)
		instance = new FenetreConteneur();
		return instance;
	}
	
	
	private static FenetreConteneur instance = null;
}


class FenetrePrincipale extends JFrame
{
	public FenetrePrincipale()
	{
		this.setJMenuBar(new barre());
		this.getContentPane().add(FenetreConteneur.getInstance());
		this.setVisible(true);
		
	}
}


class FenetreSecondaire extends JInternalFrame
{
	public FenetreSecondaire(String titre)
	{
		this.setTitle(titre);
		this.setMaximizable(true);
		this.setClosable(true);
		this.setSize(200,150);
		this.setResizable(true);
		this.setVisible(true);
		
		
		JTextArea g = new JTextArea(50,30);
		g.setLineWrap(true);
		this.getContentPane().add(g);
	}
	
}


public class feuilleMDI
{
	public static void main(String arg[])
	{
		FenetrePrincipale f = new FenetrePrincipale();
		f.setSize(750,800);
	}
}