private void jComboBox1ActionPerformed(java.awt.event.ActionEvent evt) { //výběr prováděné operace
        switch (jComboBox1.getSelectedIndex()){
            case 0:
            case 1:
            case 2:
                jPanel2.setVisible(true);
                jPanel3.setVisible(false);
                break;
            case 3:
                jPanel3.setVisible(true);
                jPanel2.setVisible(false);
                break;
            case 4:
            case 5:
                jPanel2.setVisible(false);
                jPanel3.setVisible(false);
                break;
        }
        pack();
    }