diff --git a/images/src/org/intellij/images/editor/impl/ImageFileEditorProvider.java b/images/src/org/intellij/images/editor/impl/ImageFileEditorProvider.java
index 439661afcfea..56fe8d3c2652 100644
--- a/images/src/org/intellij/images/editor/impl/ImageFileEditorProvider.java
+++ b/images/src/org/intellij/images/editor/impl/ImageFileEditorProvider.java
@@ -15,7 +15,10 @@
  */
 package org.intellij.images.editor.impl;
 
-import com.intellij.openapi.fileEditor.*;
+import com.intellij.openapi.fileEditor.FileEditor;
+import com.intellij.openapi.fileEditor.FileEditorPolicy;
+import com.intellij.openapi.fileEditor.FileEditorProvider;
+import com.intellij.openapi.fileEditor.FileEditorState;
 import com.intellij.openapi.project.DumbAware;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.Disposer;
@@ -58,7 +61,7 @@ final class ImageFileEditorProvider implements FileEditorProvider, DumbAware {
   @Override
   @NotNull
   public FileEditorState readState(@NotNull Element sourceElement, @NotNull Project project, @NotNull VirtualFile file) {
-    return new NullFileEditorState();
+    return FileEditorState.INSTANCE;
   }
 
   @Override
diff --git a/images/src/org/intellij/images/editor/impl/ImageFileEditorState.java b/images/src/org/intellij/images/editor/impl/ImageFileEditorState.java
index 6a7dab4d116a..2fdb94919abc 100644
--- a/images/src/org/intellij/images/editor/impl/ImageFileEditorState.java
+++ b/images/src/org/intellij/images/editor/impl/ImageFileEditorState.java
@@ -43,6 +43,7 @@ public class ImageFileEditorState implements TransferableFileEditorState, Serial
     this.zoomFactor = zoomFactor;
   }
 
+  @Override
   public boolean canBeMergedWith(FileEditorState otherState, FileEditorStateLevel level) {
     return otherState instanceof ImageFileEditorState;
   }
diff --git a/platform/platform-api/src/com/intellij/openapi/fileEditor/FileEditorProvider.java b/platform/platform-api/src/com/intellij/openapi/fileEditor/FileEditorProvider.java
index 8ff35a9f994a..2f6d2f611fe6 100644
--- a/platform/platform-api/src/com/intellij/openapi/fileEditor/FileEditorProvider.java
+++ b/platform/platform-api/src/com/intellij/openapi/fileEditor/FileEditorProvider.java
@@ -63,6 +63,7 @@ public interface FileEditorProvider {
 
   /**
    * Deserialize state from the specified <code>sourceElement</code>
+   * Use {@link FileEditorState#INSTANCE} as default implementation
    */
   @NotNull
   FileEditorState readState(@NotNull Element sourceElement, @NotNull Project project, @NotNull VirtualFile file);
diff --git a/platform/platform-api/src/com/intellij/openapi/fileEditor/NullFileEditorState.java b/platform/platform-api/src/com/intellij/openapi/fileEditor/NullFileEditorState.java
deleted file mode 100644
index d9c822f314cd..000000000000
--- a/platform/platform-api/src/com/intellij/openapi/fileEditor/NullFileEditorState.java
+++ /dev/null
@@ -1,23 +0,0 @@
-/*
- * Copyright 2000-2013 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package com.intellij.openapi.fileEditor;
-
-public final class NullFileEditorState implements FileEditorState {
-  @Override
-  public boolean canBeMergedWith(FileEditorState otherState, FileEditorStateLevel level) {
-    return false;
-  }
-}
\ No newline at end of file
diff --git a/platform/testFramework/src/com/intellij/mock/Mock.java b/platform/testFramework/src/com/intellij/mock/Mock.java
index 9e2a14be0711..87e13adf2473 100644
--- a/platform/testFramework/src/com/intellij/mock/Mock.java
+++ b/platform/testFramework/src/com/intellij/mock/Mock.java
@@ -78,12 +78,7 @@ public class Mock {
     @Override
     @NotNull
     public FileEditorState getState(@NotNull FileEditorStateLevel level) {
-      return new FileEditorState() {
-            @Override
-            public boolean canBeMergedWith(FileEditorState fileEditorState, FileEditorStateLevel fileEditorStateLevel) {
-                return false;
-            }
-        };
+      return FileEditorState.INSTANCE;
     }
 
     @Override
@@ -316,10 +311,10 @@ public class Mock {
 
     @Override
     @NotNull
-    public Pair<FileEditor[],FileEditorProvider[]> openFileWithProviders(@NotNull VirtualFile file,
-                                                                         boolean focusEditor,
-                                                                         boolean searchForSplitter) {
-      return Pair.create (new FileEditor[0], new FileEditorProvider [0]);
+    public Pair<FileEditor[], FileEditorProvider[]> openFileWithProviders(@NotNull VirtualFile file,
+                                                                          boolean focusEditor,
+                                                                          boolean searchForSplitter) {
+      return Pair.create(new FileEditor[0], new FileEditorProvider[0]);
     }
 
     @Override
@@ -387,11 +382,11 @@ public class Mock {
     }
 
     @Override
-    public void removeEditorAnnotation(@NotNull FileEditor editor, @NotNull JComponent annotationComoponent) {
+    public void removeEditorAnnotation(@NotNull FileEditor editor, @NotNull JComponent annotationComponent) {
     }
 
     @Override
-    public void showEditorAnnotation(@NotNull FileEditor editor, @NotNull JComponent annotationComoponent) {
+    public void showEditorAnnotation(@NotNull FileEditor editor, @NotNull JComponent annotationComponent) {
     }
 
     @Override
diff --git a/platform/util/src/com/intellij/openapi/util/Disposer.java b/platform/util/src/com/intellij/openapi/util/Disposer.java
index bb999e5a2d1f..4ddf0278a2f4 100644
--- a/platform/util/src/com/intellij/openapi/util/Disposer.java
+++ b/platform/util/src/com/intellij/openapi/util/Disposer.java
@@ -108,8 +108,8 @@ public class Disposer {
     ourTree.executeAll(disposable, true, ourDisposeAction, processUnregistered);
   }
 
-  public static void disposeChildAndReplace(@NotNull Disposable toDipose, @NotNull Disposable toReplace) {
-    ourTree.executeChildAndReplace(toDipose, toReplace, true, ourDisposeAction);
+  public static void disposeChildAndReplace(@NotNull Disposable toDispose, @NotNull Disposable toReplace) {
+    ourTree.executeChildAndReplace(toDispose, toReplace, true, ourDisposeAction);
   }
 
   @NotNull
diff --git a/plugins/ui-designer/src/com/intellij/uiDesigner/editor/MyEditorState.java b/plugins/ui-designer/src/com/intellij/uiDesigner/editor/MyEditorState.java
index fef1e13ecf91..4ecd1e465669 100644
--- a/plugins/ui-designer/src/com/intellij/uiDesigner/editor/MyEditorState.java
+++ b/plugins/ui-designer/src/com/intellij/uiDesigner/editor/MyEditorState.java
@@ -50,6 +50,7 @@ final class MyEditorState implements FileEditorState{
     return (int)(myDocumentModificationStamp ^ (myDocumentModificationStamp >>> 32));
   }
 
+  @Override
   public boolean canBeMergedWith(FileEditorState otherState, FileEditorStateLevel level) {
     return otherState instanceof MyEditorState;
   }
diff --git a/xml/dom-openapi/src/com/intellij/util/xml/ui/PerspectiveFileEditor.java b/xml/dom-openapi/src/com/intellij/util/xml/ui/PerspectiveFileEditor.java
index 5cd00515a754..7e57a41074d4 100644
--- a/xml/dom-openapi/src/com/intellij/util/xml/ui/PerspectiveFileEditor.java
+++ b/xml/dom-openapi/src/com/intellij/util/xml/ui/PerspectiveFileEditor.java
@@ -18,13 +18,13 @@ package com.intellij.util.xml.ui;
 
 import com.intellij.codeHighlighting.BackgroundEditorHighlighter;
 import com.intellij.ide.structureView.StructureViewBuilder;
+import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.editor.Document;
 import com.intellij.openapi.editor.ScrollType;
 import com.intellij.openapi.fileEditor.*;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.UserDataHolderBase;
 import com.intellij.openapi.vfs.VirtualFile;
-import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.psi.PsiDocumentManager;
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiFile;
@@ -46,7 +46,7 @@ import java.beans.PropertyChangeSupport;
  * @author Sergey.Vasiliev
  */
 abstract public class PerspectiveFileEditor extends UserDataHolderBase implements DocumentsEditor, Committable {
-  private final Wrapper myWrapprer = new Wrapper();
+  private final Wrapper myWrapper = new Wrapper();
   private boolean myInitialised = false;
 
   private final PropertyChangeSupport myPropertyChangeSupport = new PropertyChangeSupport(this);
@@ -55,22 +55,18 @@ abstract public class PerspectiveFileEditor extends UserDataHolderBase implement
   private final UndoHelper myUndoHelper;
   private boolean myInvalidated;
 
-  private static final FileEditorState FILE_EDITOR_STATE = new FileEditorState() {
-    public boolean canBeMergedWith(FileEditorState otherState, FileEditorStateLevel level) {
-      return true;
-    }
-  };
-
   protected PerspectiveFileEditor(final Project project, final VirtualFile file) {
     myProject = project;
     myUndoHelper = new UndoHelper(project, this);
     myFile = file;
 
     FileEditorManager.getInstance(myProject).addFileEditorManagerListener(new FileEditorManagerAdapter() {
+      @Override
       public void selectionChanged(@NotNull FileEditorManagerEvent event) {
         if (!isValid()) return;
 
         ApplicationManager.getApplication().invokeLater(new Runnable() {
+          @Override
           public void run() {
             if (myUndoHelper.isShowing() && !getComponent().isShowing()) {
               deselectNotify();
@@ -183,6 +179,7 @@ abstract public class PerspectiveFileEditor extends UserDataHolderBase implement
     return PsiManager.getInstance(myProject).findFile(myFile);
   }
 
+  @Override
   public final Document[] getDocuments() {
     return myUndoHelper.getDocuments();
   }
@@ -195,20 +192,24 @@ abstract public class PerspectiveFileEditor extends UserDataHolderBase implement
     return myFile;
   }
 
+  @Override
   public void dispose() {
     if (myInvalidated) return;
     myInvalidated = true;
     myUndoHelper.stopListeningDocuments();
   }
 
+  @Override
   public final boolean isModified() {
     return FileDocumentManager.getInstance().isFileModified(getVirtualFile());
   }
 
+  @Override
   public boolean isValid() {
     return getVirtualFile().isValid();
   }
 
+  @Override
   public void selectNotify() {
     if (!checkIsValid() || myInvalidated) return;
     ensureInitialized();
@@ -222,50 +223,60 @@ abstract public class PerspectiveFileEditor extends UserDataHolderBase implement
 
   protected final synchronized void ensureInitialized() {
     if (!isInitialised()) {
-      myWrapprer.setContent(createCustomComponent());
+      myWrapper.setContent(createCustomComponent());
       myInitialised = true;
     }
   }
 
+  @Override
   public void deselectNotify() {
     if (!checkIsValid() || myInvalidated) return;
     setShowing(false);
     commit();
   }
 
+  @Override
   public BackgroundEditorHighlighter getBackgroundHighlighter() {
     return null;
   }
 
+  @Override
   public FileEditorLocation getCurrentLocation() {
     return new FileEditorLocation() {
+      @Override
       @NotNull
       public FileEditor getEditor() {
         return PerspectiveFileEditor.this;
       }
 
-      public int compareTo(final FileEditorLocation fileEditorLocation) {
+      @Override
+      public int compareTo(@NotNull final FileEditorLocation fileEditorLocation) {
         return 0;
       }
     };
   }
 
+  @Override
   public StructureViewBuilder getStructureViewBuilder() {
     return null;
   }
 
+  @Override
   @NotNull
   public FileEditorState getState(@NotNull FileEditorStateLevel level) {
-    return FILE_EDITOR_STATE;
+    return FileEditorState.INSTANCE;
   }
 
+  @Override
   public void setState(@NotNull FileEditorState state) {
   }
 
+  @Override
   public void addPropertyChangeListener(@NotNull PropertyChangeListener listener) {
     myPropertyChangeSupport.addPropertyChangeListener(listener);
   }
 
+  @Override
   public void removePropertyChangeListener(@NotNull PropertyChangeListener listener) {
     myPropertyChangeSupport.removePropertyChangeListener(listener);
   }
@@ -278,6 +289,7 @@ abstract public class PerspectiveFileEditor extends UserDataHolderBase implement
     return !myInvalidated;
   }
 
+  @Override
   @NotNull
   public JComponent getComponent() {
     return getWrapper();
@@ -287,7 +299,7 @@ abstract public class PerspectiveFileEditor extends UserDataHolderBase implement
   protected abstract JComponent createCustomComponent();
 
   public Wrapper getWrapper() {
-    return myWrapprer;
+    return myWrapper;
   }
 
   protected final synchronized boolean isInitialised() {
diff --git a/xml/dom-openapi/src/com/intellij/util/xml/ui/PerspectiveFileEditorProvider.java b/xml/dom-openapi/src/com/intellij/util/xml/ui/PerspectiveFileEditorProvider.java
index c9650fc48d8e..7e4ba4cf0563 100644
--- a/xml/dom-openapi/src/com/intellij/util/xml/ui/PerspectiveFileEditorProvider.java
+++ b/xml/dom-openapi/src/com/intellij/util/xml/ui/PerspectiveFileEditorProvider.java
@@ -15,7 +15,10 @@
  */
 package com.intellij.util.xml.ui;
 
-import com.intellij.openapi.fileEditor.*;
+import com.intellij.openapi.fileEditor.FileEditor;
+import com.intellij.openapi.fileEditor.FileEditorPolicy;
+import com.intellij.openapi.fileEditor.FileEditorState;
+import com.intellij.openapi.fileEditor.WeighedFileEditorProvider;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.Disposer;
 import com.intellij.openapi.vfs.VirtualFile;
@@ -39,12 +42,7 @@ public abstract class PerspectiveFileEditorProvider extends WeighedFileEditorPro
   @Override
   @NotNull
   public FileEditorState readState(@NotNull Element sourceElement, @NotNull Project project, @NotNull VirtualFile file) {
-    return new FileEditorState() {
-      @Override
-      public boolean canBeMergedWith(FileEditorState otherState, FileEditorStateLevel level) {
-        return true;
-      }
-    };
+    return FileEditorState.INSTANCE;
   }
 
   @Override