private void configurePieChartButtonActionPerformed(
     java.awt.event.ActionEvent evt) { // GEN-FIRST:event_configurePieChartButtonActionPerformed
   if (pieChart == null) {
     pieChart = manipulator.buildPieChart(valuesFrequencies);
   }
   if (pieChartDialog != null) {
     pieChartDialog.setVisible(true);
   } else {
     pieChartDialog =
         new JFreeChartDialog(
             WindowManager.getDefault().getMainWindow(),
             pieChart.getTitle().getText(),
             pieChart,
             1000,
             1000);
   }
 } // GEN-LAST:event_configurePieChartButtonActionPerformed