diff --git a/platform/lang-impl/src/com/intellij/util/ui/tree/PerFileConfigurableBase.java b/platform/lang-impl/src/com/intellij/util/ui/tree/PerFileConfigurableBase.java
index 49943aa2ce43..841af30df412 100644
--- a/platform/lang-impl/src/com/intellij/util/ui/tree/PerFileConfigurableBase.java
+++ b/platform/lang-impl/src/com/intellij/util/ui/tree/PerFileConfigurableBase.java
@@ -724,10 +724,10 @@ public abstract class PerFileConfigurableBase<T> implements SearchableConfigurab
       }
 
       @Override
-      protected ComboBoxButton createComboBoxButton(Presentation presentation) {
+      protected @NotNull ComboBoxButton createComboBoxButton(@NotNull Presentation presentation) {
         return new ComboBoxButton(presentation) {
           @Override
-          protected JBPopup createPopup(Runnable onDispose) {
+          protected @NotNull JBPopup createPopup(Runnable onDispose) {
             JBPopup popup = createValueEditorPopup(target, value.get(), onDispose, getDataContext(), o -> {
               value.set(o);
               updateText(presentation);
diff --git a/platform/platform-api/src/com/intellij/openapi/actionSystem/ex/ComboBoxAction.java b/platform/platform-api/src/com/intellij/openapi/actionSystem/ex/ComboBoxAction.java
index 5fc3087c25d5..529a778e568d 100644
--- a/platform/platform-api/src/com/intellij/openapi/actionSystem/ex/ComboBoxAction.java
+++ b/platform/platform-api/src/com/intellij/openapi/actionSystem/ex/ComboBoxAction.java
@@ -41,6 +41,7 @@ public abstract class ComboBoxAction extends AnAction implements CustomComponent
   private static Icon myIcon;
   private static Icon myDisabledIcon;
 
+  @NotNull
   public static Icon getArrowIcon(boolean enabled) {
     if (myIcon != AllIcons.General.ArrowDown) {
       myIcon = UIManager.getIcon("ComboBoxButton.arrowIcon");
@@ -98,7 +99,8 @@ public abstract class ComboBoxAction extends AnAction implements CustomComponent
     return panel;
   }
 
-  protected ComboBoxButton createComboBoxButton(Presentation presentation) {
+  @NotNull
+  protected ComboBoxButton createComboBoxButton(@NotNull Presentation presentation) {
     return new ComboBoxButton(presentation);
   }
 
@@ -110,7 +112,7 @@ public abstract class ComboBoxAction extends AnAction implements CustomComponent
     mySmallVariant = smallVariant;
   }
 
-  public void setPopupTitle(@NlsContexts.PopupTitle String popupTitle) {
+  public void setPopupTitle(@NotNull @NlsContexts.PopupTitle String popupTitle) {
     myPopupTitle = popupTitle;
   }
 
@@ -122,7 +124,7 @@ public abstract class ComboBoxAction extends AnAction implements CustomComponent
   protected abstract DefaultActionGroup createPopupActionGroup(JComponent button);
 
   @NotNull
-  protected DefaultActionGroup createPopupActionGroup(JComponent button, @NotNull  DataContext dataContext) {
+  protected DefaultActionGroup createPopupActionGroup(@NotNull JComponent button, @NotNull  DataContext dataContext) {
     return createPopupActionGroup(button);
   }
 
@@ -143,7 +145,7 @@ public abstract class ComboBoxAction extends AnAction implements CustomComponent
     private boolean myForcePressed;
     private @TooltipTitle String myTooltipText;
 
-    public ComboBoxButton(Presentation presentation) {
+    public ComboBoxButton(@NotNull Presentation presentation) {
       myPresentation = presentation;
 
       setIcon(myPresentation.getIcon());
@@ -208,6 +210,7 @@ public abstract class ComboBoxAction extends AnAction implements CustomComponent
     }
 
     @TestOnly
+    @NotNull
     public Presentation getPresentation() {
       return myPresentation;
     }
@@ -250,10 +253,12 @@ public abstract class ComboBoxAction extends AnAction implements CustomComponent
       popup.showUnderneathOf(this);
     }
 
-    protected JBPopup createPopup(Runnable onDispose) {
+    @NotNull
+    protected JBPopup createPopup(@Nullable Runnable onDispose) {
       return createActionPopup(getDataContext(), this, onDispose);
     }
 
+    @NotNull
     protected DataContext getDataContext() {
       return ActionToolbar.getDataContextFor(this);
     }
@@ -276,7 +281,8 @@ public abstract class ComboBoxAction extends AnAction implements CustomComponent
       if (Registry.is("ide.helptooltip.enabled") && StringUtil.isNotEmpty(myTooltipText)) {
         String shortcut = KeymapUtil.getFirstKeyboardShortcutText(ComboBoxAction.this);
         new HelpTooltip().setTitle(myTooltipText).setShortcut(shortcut).installOn(this);
-      } else {
+      }
+      else {
         String tooltip = KeymapUtil.createTooltipText(myTooltipText, ComboBoxAction.this);
         setToolTipText(!tooltip.isEmpty() ? tooltip : null);
       }
@@ -374,7 +380,8 @@ public abstract class ComboBoxAction extends AnAction implements CustomComponent
       return true;
     }
 
-    @Override public void updateUI() {
+    @Override
+    public void updateUI() {
       super.updateUI();
       updateMargin();
     }
diff --git a/plugins/tasks/tasks-core/src/com/intellij/tasks/actions/SwitchTaskAction.java b/plugins/tasks/tasks-core/src/com/intellij/tasks/actions/SwitchTaskAction.java
index 560e6a18fae7..04fecce98ac9 100644
--- a/plugins/tasks/tasks-core/src/com/intellij/tasks/actions/SwitchTaskAction.java
+++ b/plugins/tasks/tasks-core/src/com/intellij/tasks/actions/SwitchTaskAction.java
@@ -50,7 +50,7 @@ public class SwitchTaskAction extends ComboBoxAction implements DumbAware {
   public JComponent createCustomComponent(@NotNull final Presentation presentation, @NotNull String place) {
     return new ComboBoxButton(presentation) {
       @Override
-      protected JBPopup createPopup(Runnable onDispose) {
+      protected @NotNull JBPopup createPopup(Runnable onDispose) {
         return SwitchTaskAction.createPopup(DataManager.getInstance().getDataContext(this), onDispose, false);
       }
     };
diff --git a/plugins/ui-designer-core/src/com/intellij/designer/actions/AbstractComboBoxAction.java b/plugins/ui-designer-core/src/com/intellij/designer/actions/AbstractComboBoxAction.java
index a7fcb14bed65..15abd5516caf 100644
--- a/plugins/ui-designer-core/src/com/intellij/designer/actions/AbstractComboBoxAction.java
+++ b/plugins/ui-designer-core/src/com/intellij/designer/actions/AbstractComboBoxAction.java
@@ -69,11 +69,11 @@ public abstract class AbstractComboBoxAction<T> extends ComboBoxAction {
   }
 
   @Override
-  protected ComboBoxButton createComboBoxButton(Presentation presentation) {
+  protected @NotNull ComboBoxButton createComboBoxButton(@NotNull Presentation presentation) {
     if (myShowDisabledActions) {
       return new ComboBoxButton(presentation) {
         @Override
-        protected JBPopup createPopup(Runnable onDispose) {
+        protected @NotNull JBPopup createPopup(Runnable onDispose) {
           ListPopup popup = JBPopupFactory.getInstance().createActionGroupPopup(null, createPopupActionGroup(this), getDataContext(), true, onDispose, getMaxRows());
           popup.setMinimumSize(new Dimension(getMinWidth(), getMinHeight()));
           return popup;