diff --git a/platform/core-impl/src/com/intellij/openapi/editor/ex/MarkupIterator.java b/platform/core-impl/src/com/intellij/openapi/editor/ex/MarkupIterator.java
index 7cc45d70c57d..990b92e97b9a 100644
--- a/platform/core-impl/src/com/intellij/openapi/editor/ex/MarkupIterator.java
+++ b/platform/core-impl/src/com/intellij/openapi/editor/ex/MarkupIterator.java
@@ -23,7 +23,7 @@ import java.util.Comparator;
 import java.util.NoSuchElementException;
 
 /**
- * An iterator you must to {@link #dispose()} after use
+ * An iterator you must {@link #dispose()} after use
  */
 public interface MarkupIterator<T> extends PeekableIterator<T> {
   void dispose();
@@ -35,7 +35,7 @@ public interface MarkupIterator<T> extends PeekableIterator<T> {
 
     @Override
     public Object peek() {
-      return null;
+      throw new NoSuchElementException();
     }
 
     @Override
diff --git a/platform/core-impl/src/com/intellij/openapi/editor/impl/RangeMarkerImpl.java b/platform/core-impl/src/com/intellij/openapi/editor/impl/RangeMarkerImpl.java
index 5bc66cc47e0e..d41f3552ea89 100644
--- a/platform/core-impl/src/com/intellij/openapi/editor/impl/RangeMarkerImpl.java
+++ b/platform/core-impl/src/com/intellij/openapi/editor/impl/RangeMarkerImpl.java
@@ -22,12 +22,11 @@ import com.intellij.openapi.editor.ex.DocumentEx;
 import com.intellij.openapi.editor.ex.RangeMarkerEx;
 import com.intellij.openapi.editor.impl.event.DocumentEventImpl;
 import com.intellij.openapi.util.*;
-import com.intellij.util.Processor;
 import org.jetbrains.annotations.NonNls;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-public class RangeMarkerImpl extends UserDataHolderBase implements RangeMarkerEx, MutableInterval {
+public class RangeMarkerImpl extends UserDataHolderBase implements RangeMarkerEx {
   private static final Logger LOG = Logger.getInstance("#com.intellij.openapi.editor.impl.RangeMarkerImpl");
 
   private final DocumentEx myDocument;
@@ -36,7 +35,7 @@ public class RangeMarkerImpl extends UserDataHolderBase implements RangeMarkerEx
   private final long myId;
   private static final StripedIDGenerator counter = new StripedIDGenerator();
 
-  protected RangeMarkerImpl(@NotNull DocumentEx document, int start, int end, boolean register) {
+  RangeMarkerImpl(@NotNull DocumentEx document, int start, int end, boolean register) {
     this(document, start, end, register, false, false);
   }
   private RangeMarkerImpl(@NotNull DocumentEx document, int start, int end, boolean register, boolean greedyToLeft, boolean greedyToRight) {
diff --git a/platform/editor-ui-ex/src/com/intellij/openapi/editor/impl/PersistentRangeHighlighterImpl.java b/platform/editor-ui-ex/src/com/intellij/openapi/editor/impl/PersistentRangeHighlighterImpl.java
index 4cde8efbcf51..8ec499d14c14 100644
--- a/platform/editor-ui-ex/src/com/intellij/openapi/editor/impl/PersistentRangeHighlighterImpl.java
+++ b/platform/editor-ui-ex/src/com/intellij/openapi/editor/impl/PersistentRangeHighlighterImpl.java
@@ -17,7 +17,6 @@ package com.intellij.openapi.editor.impl;
 
 import com.intellij.openapi.editor.event.DocumentEvent;
 import com.intellij.openapi.editor.ex.DocumentEx;
-import com.intellij.openapi.editor.ex.RangeHighlighterEx;
 import com.intellij.openapi.editor.impl.event.DocumentEventImpl;
 import com.intellij.openapi.editor.markup.HighlighterTargetArea;
 import com.intellij.openapi.editor.markup.MarkupModel;
@@ -31,7 +30,7 @@ import org.jetbrains.annotations.Nullable;
  * Implementation of the markup element for the editor and document.
  * @author max
  */
-class PersistentRangeHighlighterImpl extends RangeHighlighterImpl implements RangeHighlighterEx {
+class PersistentRangeHighlighterImpl extends RangeHighlighterImpl {
   private int myLine; // for PersistentRangeHighlighterImpl only
   static PersistentRangeHighlighterImpl create(@NotNull MarkupModel model,
                                                int offset,
diff --git a/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorFilteringMarkupModelEx.java b/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorFilteringMarkupModelEx.java
index d4751bfd18a2..b19f586b9992 100644
--- a/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorFilteringMarkupModelEx.java
+++ b/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorFilteringMarkupModelEx.java
@@ -40,9 +40,9 @@ public class EditorFilteringMarkupModelEx implements MarkupModelEx {
   @NotNull private final EditorImpl myEditor;
   @NotNull private final MarkupModelEx myDelegate;
 
-  private final Condition<RangeHighlighter> IS_AVAILABLE = highlighter -> isAvailable(highlighter);
+  private final Condition<RangeHighlighter> IS_AVAILABLE = this::isAvailable;
 
-  public EditorFilteringMarkupModelEx(@NotNull EditorImpl editor, @NotNull MarkupModelEx delegate) {
+  EditorFilteringMarkupModelEx(@NotNull EditorImpl editor, @NotNull MarkupModelEx delegate) {
     myEditor = editor;
     myDelegate = delegate;
   }
@@ -94,9 +94,9 @@ public class EditorFilteringMarkupModelEx implements MarkupModelEx {
 
   private class MyFilteringIterator extends FilteringIterator<RangeHighlighterEx, RangeHighlighterEx>
     implements MarkupIterator<RangeHighlighterEx> {
-    private MarkupIterator<RangeHighlighterEx> myDelegate;
+    private final MarkupIterator<RangeHighlighterEx> myDelegate;
 
-    public MyFilteringIterator(@NotNull MarkupIterator<RangeHighlighterEx> delegate) {
+    MyFilteringIterator(@NotNull MarkupIterator<RangeHighlighterEx> delegate) {
       super(delegate, IS_AVAILABLE);
       myDelegate = delegate;
     }
diff --git a/platform/usageView/src/com/intellij/usages/UsageView.java b/platform/usageView/src/com/intellij/usages/UsageView.java
index e0a3761c6db0..82fa8851feb7 100644
--- a/platform/usageView/src/com/intellij/usages/UsageView.java
+++ b/platform/usageView/src/com/intellij/usages/UsageView.java
@@ -32,13 +32,13 @@ import java.util.Set;
  */
 public interface UsageView extends Disposable {
   /**
-   * Returns {@link com.intellij.usages.UsageTarget} to look usages for
+   * Returns {@link UsageTarget} to look usages for
    */
   DataKey<UsageTarget[]> USAGE_TARGETS_KEY = DataKey.create("usageTarget");
   @Deprecated String USAGE_TARGETS = USAGE_TARGETS_KEY.getName();
 
   /**
-   * Returns {@link com.intellij.usages.Usage} which are selected in usage view
+   * Returns {@link Usage} which are selected in usage view
    */
   DataKey<Usage[]> USAGES_KEY = DataKey.create("usages");
   @Deprecated String USAGES = USAGES_KEY.getName();
diff --git a/platform/util/src/com/intellij/util/containers/FilteringIterator.java b/platform/util/src/com/intellij/util/containers/FilteringIterator.java
index ca23a0c5243f..5ec5de63142e 100644
--- a/platform/util/src/com/intellij/util/containers/FilteringIterator.java
+++ b/platform/util/src/com/intellij/util/containers/FilteringIterator.java
@@ -34,12 +34,6 @@ public class FilteringIterator<Dom, E extends Dom> implements PeekableIterator<E
   private boolean myCurrentIsValid;
   private Dom myCurrent;
   private Boolean myCurrentPassedFilter;
-  public static final Condition NOT_NULL = new Condition() {
-    @Override
-    public boolean value(Object t) {
-      return t != null;
-    }
-  };
 
   public FilteringIterator(@NotNull Iterator<Dom> delegate, @NotNull Condition<? super Dom> condition) {
     myDelegate = delegate;
@@ -76,7 +70,7 @@ public class FilteringIterator<Dom, E extends Dom> implements PeekableIterator<E
   private boolean isCurrentPassesFilter() {
     if (myCurrentPassedFilter != null) return myCurrentPassedFilter.booleanValue();
     boolean passed = myCondition.value(myCurrent);
-    myCurrentPassedFilter = Boolean.valueOf(passed);
+    myCurrentPassedFilter = passed;
     return passed;
   }
 
@@ -98,13 +92,14 @@ public class FilteringIterator<Dom, E extends Dom> implements PeekableIterator<E
     myDelegate.remove();
   }
 
+  @Override
   public E peek() {
     if (!hasNext()) throw new NoSuchElementException();
     return (E)myCurrent;
   }
 
   public static <T> Iterator<T> skipNulls(Iterator<T> iterator) {
-    return create(iterator, NOT_NULL);
+    return create(iterator, Conditions.<T>notNull());
   }
 
   public static <Dom, T extends Dom> Iterator<T> create(Iterator<Dom> iterator, Condition<? super Dom> condition) {
diff --git a/platform/util/src/com/intellij/util/containers/PeekableIterator.java b/platform/util/src/com/intellij/util/containers/PeekableIterator.java
index 19cc218491b0..563d4ce643e3 100644
--- a/platform/util/src/com/intellij/util/containers/PeekableIterator.java
+++ b/platform/util/src/com/intellij/util/containers/PeekableIterator.java
@@ -16,14 +16,19 @@
 package com.intellij.util.containers;
 
 import java.util.Iterator;
+import java.util.NoSuchElementException;
 
+/**
+ * An iterator with additional ability to {@link #peek()} the current element without moving the cursor.
+ * Upon creation, {@link #peek()} returns the first element, after {@link #hasNext()} returns false might throw {@link NoSuchElementException}.
+ */
 public interface PeekableIterator<T> extends Iterator<T> {
-  T peek();
+  T peek() throws NoSuchElementException;
 
   PeekableIterator EMPTY = new PeekableIterator() {
     @Override
     public Object peek() {
-      return null;
+      throw new NoSuchElementException();
     }
 
     @Override