EQUATIONS DU 2ND DEGRÉ (AVEC COMPLEXES)

import java.io.*;
import java.lang.*;
import java.lang.Math.*;
import java.awt.*;
import javax.swing.JOptionPane;

class Complexes extends Frame 
{
	public int x,y,z;
	
	
	Complexes()
	{
		String a1,b1,c1;		
		a1 = JOptionPane.showInputDialog(null,"Veuillez entrer la valeur de a : ", "Input",JOptionPane.INFORMATION_MESSAGE);
		if (a1 == null)
		System.exit(0);
		b1 = JOptionPane.showInputDialog(null,"Veuillez entrer la valeur de b : ", "Input",JOptionPane.INFORMATION_MESSAGE);
		if (b1 == null)
		System.exit(0);
		c1 = JOptionPane.showInputDialog(null,"Veuillez entrer la valeur de c : ", "Input",JOptionPane.INFORMATION_MESSAGE);
		if (c1 == null)
		System.exit(0);
		x=Integer.parseInt(a1);
		y=Integer.parseInt(b1);
		z=Integer.parseInt(c1);
	}
	double Delta()
	{
		double d;
		d = y*y-4*x*z;
		return d;
	}
	double x1(double de)
	{
		return (-y-java.lang.Math.sqrt(de))/(2*x);
	}
	double x2(double de)
	{
		return (-y+java.lang.Math.sqrt(de))/(2*x);
	}
	double x3()
	{
		return (-y/(2*x));
	}
	double xc(double de)
	{
		return (java.lang.Math.sqrt(-de)/(2*x));
	}

}
class Prog 
{ 	
	public static void main(String arg[])
	{
		int retour=JOptionPane.NO_OPTION;
		double s;
		double x1,x2;
		Frame f;
		Panel p1;
		
		while (retour!=JOptionPane.YES_OPTION)
		{
		f = new Frame("Résolution d'une equation du type ax²+bx+c=0");
		p1 = new Panel();
		p1.setLayout(new BorderLayout(10,10));
		f.add("North",new Label("Résolution d'une equation du type ax²+bx+c=0"));
		Complexes pol;
		pol = new Complexes();
		s = pol.Delta();
		f.add("West",new Label("Delta = "+ s));
		if (s>0)
		{
			x1= pol.x1(s);
			x2= pol.x2(s);
			f.add("South",new Label("Deux solutions   :   x1  =  "+ x1+"    x2  =  "+ x2));
		}
		if (s==0)
		{
			x1=pol.x3();
			f.add("South",new Label("La solution est : x = " + x1));
		}
		if (s<0)
		{
			x1=pol.x3();
			x2=pol.xc(s);
			f.add("South",new Label("Deux solutions   :   x1 = "+ x1+" + i "+ x2+"   x2 = "+ x1+" - i "+x2));
		}	
		f.pack();
		f.show();
		retour=JOptionPane.showConfirmDialog(null,"Voulez-vous quitter ?", "Hey!",JOptionPane.YES_NO_OPTION);
		f.dispose();
		}
		System.exit(0);
		
	}
}