private void btncalcularActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_btncalcularActionPerformed
      
     String registro;
     
      costo=0;
      
      if(chbxlapto.isSelected()){
      costo=costo + lapto;
      }
      if(chbxtv.isSelected()){
      costo=costo + tv;
      }
      if(chbxdisco.isSelected()){
      costo=costo + disco;
      }
      if(chbxequipo.isSelected()){
      costo=costo + equipo;
      }
      double igv=costo*0.18;
      txtsubtotal.setText(String.valueOf(costo));
      txtigv.setText(String.valueOf(igv));
      txttotal.setText(String.valueOf(costo+igv));
      registro=txtregistro.getText()+ " dni " +txtdni.getText()+ " nombre " +txtnombre.getText()+" direccion "+txtdireccion.getText()+ "subtotal " +txtsubtotal.getText()+ " igv " +txtigv.getText()+ " total " + txttotal.getText();
     
      txtregistro.setText(registro+"\n");
    }//GEN-LAST:event_btncalcularActionPerformed