Ecuacion De 2do Grado

import java.awt.GridLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;

public class Ecuacion2do extends JFrame {
  private static final long serialVersionUID = 1L;
  Double A;
  Double B;
  Double C;
  JLabel lblA,lblB,lblC,lblx1,lblx2,lblvA,lblvB,lblvC,lblvDet;
  JTextField txtA,txtB,txtC;
  JButton btnAceptar, btnCancelar;
 
 public Ecuacion2do( ) {
  setTitle("Solucion");
  setSize(250,200);
  setDefaultCloseOperation(EXIT_ON_CLOSE);
  setLocationRelativeTo(null);
  dibujarIntefaz( );    }
 
 public void dibujarIntefaz( ) {
  getContentPane( ).setLayout(new GridLayout(7,2));
 
  lblA = new JLabel("Valor de A");
  getContentPane( ).add(lblA);
 
  txtA = new JTextField();
  getContentPane( ).add(txtA); 
 
  lblB = new JLabel("Valor de B");
  getContentPane( ).add(lblB);
 
  txtB = new JTextField( );
  getContentPane( ).add(txtB);
 
  lblC = new JLabel("Valor de C");
  getContentPane( ).add(lblC);
 
  txtC = new JTextField();
  getContentPane( ).add(txtC);
  lblx1 = new JLabel("x1 = ");
  getContentPane( ).add(lblx1);
  lblx2 = new JLabel("x2 = ");
  getContentPane( ).add(lblx2);
 
  lblvA = new JLabel("vA");
  getContentPane( ).add(lblvA);
 
  lblvB = new JLabel("vB");
  getContentPane( ).add(lblvB);
 
  lblvC = new JLabel("vC");
  getContentPane( ).add(lblvC);
 
  lblvDet = new JLabel("vDet");
  getContentPane( ).add(lblvDet);
  
  btnAceptar = new JButton("Resolver");
  getContentPane( ).add(btnAceptar);
 
  btnCancelar = new JButton("Cancelar");
  getContentPane( ).add(btnCancelar);
   
  btnCancelar.addActionListener(new java.awt.event.ActionListener( ) {  
   public void actionPerformed(java.awt.event.ActionEvent e) {
    System.exit(0);     }     });
 
  btnAceptar.addActionListener(new java.awt.event.ActionListener( ) {  
   public void actionPerformed(java.awt.event.ActionEvent e) {
     String msj=" ";
   
    if(txtA.getText().isEmpty( ) ) {
     msj +="Falta el valor de A\n";  }
   
    if(txtB.getText().isEmpty( ) ) {
     msj +="Falta el valor de B\n";  }   
   
    if(txtC.getText().isEmpty( ) ) {
     msj +="Falta el valor de C\n";  }
   
    A = Double.parseDouble(txtA.getText( ) );
    B = Double.parseDouble(txtB.getText( ) );
    C = Double.parseDouble(txtC.getText( ) );
   
    lblvA.setText("A = " + txtA.getText( ) );
    lblvB.setText("B = " +txtB.getText( ) );
    lblvC.setText("C = " +txtC.getText( ) );
    lblvDet.setText("Det = " + determinante( ) );
    if (msj.isEmpty( )) {
    
     A = Double.parseDouble(txtA.getText( ) );
     B = Double.parseDouble(txtB.getText( ) );
     C = Double.parseDouble(txtC.getText( ) );
     Double miSol[ ] = Solucion( );
    
     if (miSol[0] == 100.0) {
      lblx1.setText("Sin solucion");
      lblx2.setText("Sin solucion"); }

 else {
      lblx1.setText("X1 = " + miSol[0].toString( ) );
      lblx2.setText("X2 = " + miSol[1].toString( ) );   }  }

 else {
     javax.swing.JOptionPane.showMessageDialog(null, msj);  }  }  });
   }
 public Double determinante( ) {
  return (B * B - 4 * A * C);  }
  public Double[ ] Solucion()  {
  Double Sol[ ] = new Double[2];
 

  if (determinante( ) == 0) {
   Sol[0] = -B/2*A;
   Sol[1] = Sol[0];    }
 
  if (determinante() > 0) {

   Sol[0] = (-B + Math.sqrt(determinante( ) ) );
   Sol[0] = Sol[0]/(2*A);     
   Sol[1] = (-B - Math.sqrt(determinante( ) ) );
   Sol[1] = Sol[1]/(2*A);    }
   
  if (determinante() < 0) {
   Sol[0] = 100.0;
   Sol[1] = Sol[0];   } 
   return Sol;  }
 
 public static void main(String args[ ]) {
  new Ecuacion2do( ).setVisible(true);  }  }