Use model instead JToggleButton cast.

src/com/bulenkov/darcula/ui/DarculaButtonUI.java

@@ -42,14 +42,16 @@ public class DarculaButtonUI extends BasicButtonUI {
 
   @Override
   public void paint(Graphics g, JComponent c) {
+    final AbstractButton button = (AbstractButton) c;
+    final ButtonModel model = button.getModel();
     final Border border = c.getBorder();
     final GraphicsConfig config = GraphicsUtil.setupAAPainting(g);
     final boolean square = isSquare(c);
-    if (c.isEnabled() && border != null && ((AbstractButton)c).isContentAreaFilled()) {
+    if (c.isEnabled() && border != null && button.isContentAreaFilled()) {
       final Insets ins = border.getBorderInsets(c);
       final int yOff = (ins.top + ins.bottom) / 4;
       if (!square) {
-        if (c instanceof JButton && ((JButton)c).isDefaultButton() || c instanceof JToggleButton && ((JToggleButton)c).isSelected()) {
+        if (c instanceof JButton && ((JButton)c).isDefaultButton() || model.isSelected()) {
           ((Graphics2D)g).setPaint(new GradientPaint(0, 0, getSelectedButtonColor1(), 0, c.getHeight(), getSelectedButtonColor2()));
         }
         else {
@@ -63,8 +65,8 @@ public class DarculaButtonUI extends BasicButtonUI {
   }
 
   protected void paintText(Graphics g, JComponent c, Rectangle textRect, String text) {
-    AbstractButton button = (AbstractButton)c;
-    ButtonModel model = button.getModel();
+    final AbstractButton button = (AbstractButton)c;
+    final ButtonModel model = button.getModel();
     Color fg = button.getForeground();
     if (fg instanceof UIResource && button instanceof JButton && ((JButton)button).isDefaultButton()) {
       final Color selectedFg = UIManager.getColor("Button.darcula.selectedButtonForeground");