diff --git a/platform/platform-impl/src/com/intellij/openapi/diff/actions/HighlightModeAction.java b/platform/platform-impl/src/com/intellij/openapi/diff/actions/HighlightModeAction.java
index 06e25a95fe57..5c7760fa117c 100644
--- a/platform/platform-impl/src/com/intellij/openapi/diff/actions/HighlightModeAction.java
+++ b/platform/platform-impl/src/com/intellij/openapi/diff/actions/HighlightModeAction.java
@@ -26,6 +26,7 @@ import com.intellij.openapi.diff.ex.DiffPanelEx;
 import com.intellij.openapi.diff.impl.DiffPanelImpl;
 import com.intellij.openapi.diff.impl.processing.HighlightMode;
 import com.intellij.openapi.project.DumbAware;
+import com.intellij.openapi.project.DumbAwareAction;
 import com.intellij.util.containers.HashMap;
 import org.jetbrains.annotations.NotNull;
 
@@ -85,7 +86,7 @@ public class HighlightModeAction extends ComboBoxAction implements DumbAware {
     }
   }
 
-  private static class SetHighlightModeAction extends AnAction implements DumbAware {
+  private static class SetHighlightModeAction extends DumbAwareAction {
     private final HighlightMode myHighlightMode;
 
     public SetHighlightModeAction(String text, HighlightMode mode) {
diff --git a/platform/platform-impl/src/com/intellij/openapi/diff/actions/IgnoreWhiteSpacesAction.java b/platform/platform-impl/src/com/intellij/openapi/diff/actions/IgnoreWhiteSpacesAction.java
index 6a68ad75d5d8..d47067167966 100644
--- a/platform/platform-impl/src/com/intellij/openapi/diff/actions/IgnoreWhiteSpacesAction.java
+++ b/platform/platform-impl/src/com/intellij/openapi/diff/actions/IgnoreWhiteSpacesAction.java
@@ -26,6 +26,7 @@ import com.intellij.openapi.diff.ex.DiffPanelEx;
 import com.intellij.openapi.diff.impl.ComparisonPolicy;
 import com.intellij.openapi.diff.impl.DiffPanelImpl;
 import com.intellij.openapi.project.DumbAware;
+import com.intellij.openapi.project.DumbAwareAction;
 import com.intellij.util.containers.HashMap;
 import org.jetbrains.annotations.NotNull;
 
@@ -82,7 +83,7 @@ public class IgnoreWhiteSpacesAction extends ComboBoxAction implements DumbAware
     }
   }
 
-  private static class IgnoringPolicyAction extends AnAction implements DumbAware {
+  private static class IgnoringPolicyAction extends DumbAwareAction {
     private final ComparisonPolicy myPolicy;
 
     public IgnoringPolicyAction(String text, ComparisonPolicy policy) {
diff --git a/platform/platform-impl/src/com/intellij/openapi/diff/actions/ToggleAutoScrollAction.java b/platform/platform-impl/src/com/intellij/openapi/diff/actions/ToggleAutoScrollAction.java
index 04ec31e10ff6..407a19154a51 100644
--- a/platform/platform-impl/src/com/intellij/openapi/diff/actions/ToggleAutoScrollAction.java
+++ b/platform/platform-impl/src/com/intellij/openapi/diff/actions/ToggleAutoScrollAction.java
@@ -22,8 +22,6 @@ import com.intellij.openapi.diff.impl.DiffPanelImpl;
 import com.intellij.openapi.project.DumbAware;
 import com.intellij.ui.ToggleActionButton;
 
-import javax.swing.*;
-
 public class ToggleAutoScrollAction extends ToggleActionButton implements DumbAware {
   public ToggleAutoScrollAction() {
     super("Auto Scroll", AllIcons.General.AutoscrollToSource);
@@ -32,12 +30,7 @@ public class ToggleAutoScrollAction extends ToggleActionButton implements DumbAw
   @Override
   public boolean isSelected(AnActionEvent e) {
     DiffPanelEx diffPanel = DiffPanelImpl.fromDataContext(e.getDataContext());
-    if (diffPanel != null) {
-      return diffPanel.isAutoScrollEnabled();
-    }
-    else {
-      return true;
-    }
+    return diffPanel == null || diffPanel.isAutoScrollEnabled();
   }
 
   @Override
diff --git a/platform/platform-impl/src/com/intellij/openapi/diff/ex/DiffPanelEx.java b/platform/platform-impl/src/com/intellij/openapi/diff/ex/DiffPanelEx.java
index 933d017be2ef..bf07a4ad2cd1 100644
--- a/platform/platform-impl/src/com/intellij/openapi/diff/ex/DiffPanelEx.java
+++ b/platform/platform-impl/src/com/intellij/openapi/diff/ex/DiffPanelEx.java
@@ -29,6 +29,7 @@ import com.intellij.openapi.diff.DiffPanel;
 import com.intellij.openapi.diff.impl.ComparisonPolicy;
 import com.intellij.openapi.diff.impl.processing.HighlightMode;
 import com.intellij.openapi.editor.Editor;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 public interface DiffPanelEx extends DiffPanel, Disposable {
@@ -47,7 +48,8 @@ public interface DiffPanelEx extends DiffPanel, Disposable {
 
   boolean isAutoScrollEnabled();
 
-  void setHighlightMode(HighlightMode highlightMode);
+  void setHighlightMode(@NotNull HighlightMode highlightMode);
 
+  @NotNull
   HighlightMode getHighlightMode();
 }
diff --git a/platform/platform-impl/src/com/intellij/openapi/diff/impl/DiffPanelImpl.java b/platform/platform-impl/src/com/intellij/openapi/diff/impl/DiffPanelImpl.java
index 913d5e7cc8f9..b2bd342e6696 100644
--- a/platform/platform-impl/src/com/intellij/openapi/diff/impl/DiffPanelImpl.java
+++ b/platform/platform-impl/src/com/intellij/openapi/diff/impl/DiffPanelImpl.java
@@ -484,11 +484,12 @@ public class DiffPanelImpl implements DiffPanelEx, ContentChangeListener, TwoSid
     setComparisonPolicy(comparisonPolicy, true);
   }
 
-  public void setHighlightMode(HighlightMode highlightMode) {
+  public void setHighlightMode(@NotNull HighlightMode highlightMode) {
     myData.setHighlightMode(highlightMode);
     rediff();
   }
 
+  @NotNull
   public HighlightMode getHighlightMode() {
     return myData.getHighlightMode();
   }
diff --git a/platform/platform-impl/src/com/intellij/openapi/diff/impl/highlighting/SimpleDiffPanelState.java b/platform/platform-impl/src/com/intellij/openapi/diff/impl/highlighting/SimpleDiffPanelState.java
index d90005d70678..14c235470347 100644
--- a/platform/platform-impl/src/com/intellij/openapi/diff/impl/highlighting/SimpleDiffPanelState.java
+++ b/platform/platform-impl/src/com/intellij/openapi/diff/impl/highlighting/SimpleDiffPanelState.java
@@ -19,10 +19,7 @@ import com.intellij.openapi.Disposable;
 import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.diff.impl.ComparisonPolicy;
 import com.intellij.openapi.diff.impl.ContentChangeListener;
-import com.intellij.openapi.diff.impl.fragments.FragmentHighlighterImpl;
-import com.intellij.openapi.diff.impl.fragments.FragmentList;
-import com.intellij.openapi.diff.impl.fragments.FragmentListImpl;
-import com.intellij.openapi.diff.impl.fragments.LineFragment;
+import com.intellij.openapi.diff.impl.fragments.*;
 import com.intellij.openapi.diff.impl.processing.DiffPolicy;
 import com.intellij.openapi.diff.impl.processing.HighlightMode;
 import com.intellij.openapi.diff.impl.processing.TextCompareProcessor;
@@ -33,6 +30,7 @@ import com.intellij.util.diff.FilesTooBigForDiffException;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Iterator;
 
 public abstract class SimpleDiffPanelState implements Disposable  {
@@ -117,7 +115,7 @@ public abstract class SimpleDiffPanelState implements Disposable  {
     }
 
     if (myHighlightMode == HighlightMode.NO_HIGHLIGHTING) {
-      return LineBlocks.fromLineFragments(new ArrayList<LineFragment>());
+      return LineBlocks.fromLineFragments(Collections.<LineFragment>emptyList());
     }
 
     return addMarkup(new TextCompareProcessor(myComparisonPolicy, myDiffPolicy, myHighlightMode == HighlightMode.BY_WORD)
diff --git a/platform/platform-impl/src/com/intellij/openapi/diff/impl/splitter/LineBlocks.java b/platform/platform-impl/src/com/intellij/openapi/diff/impl/splitter/LineBlocks.java
index 3046c873f41a..d89bc2785c83 100644
--- a/platform/platform-impl/src/com/intellij/openapi/diff/impl/splitter/LineBlocks.java
+++ b/platform/platform-impl/src/com/intellij/openapi/diff/impl/splitter/LineBlocks.java
@@ -165,7 +165,7 @@ public class LineBlocks {
     return LinearTransformation.oneToOne(location, leftInterval.getStart(), rightInterval);
   }
 
-  public static LineBlocks fromLineFragments(ArrayList<LineFragment> lines) {
+  public static LineBlocks fromLineFragments(List<LineFragment> lines) {
     ArrayList<LineBlock> filtered = new ArrayList<LineBlock>();
     for (LineFragment fragment : lines) {
       if (fragment.getType() != null) filtered.add(fragment);