diff --git a/platform/platform-api/src/com/intellij/openapi/diff/BinaryContent.java b/platform/platform-api/src/com/intellij/openapi/diff/BinaryContent.java
index 218e11d32fa3..849dd4cbc4d8 100644
--- a/platform/platform-api/src/com/intellij/openapi/diff/BinaryContent.java
+++ b/platform/platform-api/src/com/intellij/openapi/diff/BinaryContent.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2009 JetBrains s.r.o.
+ * 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.
@@ -37,6 +37,7 @@ import java.nio.charset.IllegalCharsetNameException;
  * Represents bytes as content. May has text representaion.
  */
 public class BinaryContent extends DiffContent {
+  @NotNull
   private final FileType myFileType;
   private final byte[] myBytes;
   private final Charset myCharset;
@@ -44,8 +45,6 @@ public class BinaryContent extends DiffContent {
   private String myFilePath;
 
   /**
-   *
-   * @param bytes
    * @param charset use to convert bytes to String. null means bytes can't be converted to text.
    * Has no sense if fileType.isBinary()
    * @param fileType type of content
@@ -66,6 +65,7 @@ public class BinaryContent extends DiffContent {
     myFilePath = filePath;
   }
 
+  @Override
   @SuppressWarnings({"EmptyCatchBlock"})
   @Nullable
   public Document getDocument() {
@@ -98,10 +98,12 @@ public class BinaryContent extends DiffContent {
   /**
    * @return null
    */
+  @Override
   public OpenFileDescriptor getOpenFileDescriptor(int offset) {
     return null;
   }
 
+  @Override
   @Nullable
   public VirtualFile getFile() {
     if (myFileType instanceof UIBasedFileType) {
@@ -115,15 +117,18 @@ public class BinaryContent extends DiffContent {
     return null;
   }
 
-  @Nullable
+  @Override
+  @NotNull
   public FileType getContentType() {
     return myFileType;
   }
 
+  @Override
   public byte[] getBytes() throws IOException {
     return myBytes;
   }
 
+  @Override
   public boolean isBinary() {
     return myCharset == null;
   }
diff --git a/platform/platform-api/src/com/intellij/openapi/diff/DiffContent.java b/platform/platform-api/src/com/intellij/openapi/diff/DiffContent.java
index 1dc8c4454f09..b54a961188df 100644
--- a/platform/platform-api/src/com/intellij/openapi/diff/DiffContent.java
+++ b/platform/platform-api/src/com/intellij/openapi/diff/DiffContent.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2009 JetBrains s.r.o.
+ * 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.
@@ -123,8 +123,6 @@ public abstract class DiffContent {
   /**
    * Creates DiffContent associated with given file.
    *
-   * @param project
-   * @param file
    * @return content associated with file
    */
   public static FileContent fromFile(Project project, VirtualFile file) {
@@ -134,8 +132,6 @@ public abstract class DiffContent {
   /**
    * Creates DiffContent associated with given document
    *
-   * @param project
-   * @param document
    * @return content associated with document
    */
   public static DocumentContent fromDocument(Project project, Document document) {
diff --git a/platform/platform-api/src/com/intellij/openapi/diff/DocumentContent.java b/platform/platform-api/src/com/intellij/openapi/diff/DocumentContent.java
index 77477775a97b..0e3e7b91e7c6 100644
--- a/platform/platform-api/src/com/intellij/openapi/diff/DocumentContent.java
+++ b/platform/platform-api/src/com/intellij/openapi/diff/DocumentContent.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2009 JetBrains s.r.o.
+ * 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.
@@ -28,9 +28,9 @@ import org.jetbrains.annotations.Nullable;
 public class DocumentContent extends DiffContent {
   private final Document myDocument;
   private final VirtualFile myFile;
-  private final FileType myOverridenType;
-  private Project myProject;
-  private FileDocumentManager myDocumentManager;
+  private final FileType myOverriddenType;
+  private final Project myProject;
+  private final FileDocumentManager myDocumentManager;
 
   public DocumentContent(Project project, Document document) {
     this(project, document, null);
@@ -41,21 +41,24 @@ public class DocumentContent extends DiffContent {
     myDocument = document;
     myDocumentManager = FileDocumentManager.getInstance();
     myFile = myDocumentManager.getFile(document);
-    myOverridenType = type;
+    myOverriddenType = type;
   }
 
-  public DocumentContent(Document document) {
+  public DocumentContent(@NotNull Document document) {
     this(null, document, null);
   }
 
-  public DocumentContent(Document document, FileType type) {
+  public DocumentContent(@NotNull Document document, @NotNull FileType type) {
     this(null, document, type);
   }
 
+  @Override
+  @NotNull
   public Document getDocument() {
     return myDocument;
   }
 
+  @Override
   public OpenFileDescriptor getOpenFileDescriptor(int offset) {
     VirtualFile file = getFile();
     if (file == null) return null;
@@ -63,15 +66,18 @@ public class DocumentContent extends DiffContent {
     return new OpenFileDescriptor(myProject, file, offset);
   }
 
+  @Override
   public VirtualFile getFile() {
     return myFile;
   }
 
+  @Override
   @Nullable
   public FileType getContentType() {
-    return myOverridenType == null ? DiffContentUtil.getContentType(getFile()) : myOverridenType;
+    return myOverriddenType == null ? DiffContentUtil.getContentType(getFile()) : myOverriddenType;
   }
 
+  @Override
   public byte[] getBytes() {
     return myDocument.getText().getBytes();
   }
diff --git a/platform/platform-api/src/com/intellij/openapi/diff/DocumentsSynchronizer.java b/platform/platform-api/src/com/intellij/openapi/diff/DocumentsSynchronizer.java
index b0e48b756184..618da1747700 100644
--- a/platform/platform-api/src/com/intellij/openapi/diff/DocumentsSynchronizer.java
+++ b/platform/platform-api/src/com/intellij/openapi/diff/DocumentsSynchronizer.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2009 JetBrains s.r.o.
+ * 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.
@@ -70,6 +70,7 @@ abstract class DocumentsSynchronizer {
 
   protected abstract Document createOriginal();
 
+  @NotNull
   protected abstract Document createCopy();
 
   protected void replaceString(@NotNull final Document document, final int startOffset, final int endOffset, @NotNull final String newText) {
@@ -110,7 +111,7 @@ abstract class DocumentsSynchronizer {
   private void startListen() {
     final Document original = getOriginal();
     final Document copy = getCopy();
-    if (original == null || copy == null) return;
+    if (original == null) return;
 
     beforeListenersAttached(original, copy);
     original.addDocumentListener(myOriginalListener);
@@ -138,6 +139,7 @@ abstract class DocumentsSynchronizer {
     return myOriginal;
   }
 
+  @NotNull
   public Document getCopy() {
     if (myCopy == null) myCopy = createCopy();
     return myCopy;
diff --git a/platform/platform-api/src/com/intellij/openapi/diff/FileContent.java b/platform/platform-api/src/com/intellij/openapi/diff/FileContent.java
index f7a27694fc65..80157e6bb4ed 100644
--- a/platform/platform-api/src/com/intellij/openapi/diff/FileContent.java
+++ b/platform/platform-api/src/com/intellij/openapi/diff/FileContent.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2009 JetBrains s.r.o.
+ * 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.
@@ -44,6 +44,7 @@ public class FileContent extends DiffContent {
     myType = detectType(file);
   }
 
+  @Override
   public Document getDocument() {
     if (myDocument == null && DiffContentUtil.isTextFile(myFile)) {
       myDocument = FileDocumentManager.getInstance().getDocument(myFile);
@@ -51,26 +52,31 @@ public class FileContent extends DiffContent {
     return myDocument;
   }
 
+  @Override
   public OpenFileDescriptor getOpenFileDescriptor(int offset) {
     return new OpenFileDescriptor(myProject, myFile, offset);
   }
 
+  @Override
   @NotNull
   public VirtualFile getFile() {
     return myFile;
   }
 
+  @Override
   @Nullable
   public FileType getContentType() {
     FileType type = myFile.getFileType();
     return isUnknown(type) ? myType : type;
   }
 
+  @Override
   public byte[] getBytes() throws IOException {
     if (myFile.isDirectory()) return null;
     return myFile.contentsToByteArray();
   }
 
+  @Override
   public boolean isBinary() {
     if (myFile.isDirectory()) return false;
     if (myType != null && !myType.isBinary()) {
diff --git a/platform/platform-api/src/com/intellij/openapi/diff/FragmentContent.java b/platform/platform-api/src/com/intellij/openapi/diff/FragmentContent.java
index 6c40b3797efb..9a176e37aaf4 100644
--- a/platform/platform-api/src/com/intellij/openapi/diff/FragmentContent.java
+++ b/platform/platform-api/src/com/intellij/openapi/diff/FragmentContent.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2009 JetBrains s.r.o.
+ * 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.
@@ -57,7 +57,7 @@ public class FragmentContent extends DiffContent {
     this(original, range, project, (FileType)null);
   }
 
-  private String subText(Document document, int startOffset, int length) {
+  private static String subText(Document document, int startOffset, int length) {
     return document.getCharsSequence().subSequence(startOffset, startOffset + length).toString();
   }
 
@@ -70,6 +70,7 @@ public class FragmentContent extends DiffContent {
   }
 
   @Override
+  @NotNull
   public Document getDocument() {
     return mySynchonizer.getCopy();
   }
@@ -125,12 +126,12 @@ public class FragmentContent extends DiffContent {
 
     @Override
     protected void beforeListenersAttached(@NotNull Document original, @NotNull Document copy) {
-      boolean writable = copy.isWritable();
-      if (!writable) {
+      boolean readOnly = !copy.isWritable();
+      if (readOnly) {
         copy.setReadOnly(false);
       }
       replaceString(copy, 0, copy.getTextLength(), subText(original, myRangeMarker.getStartOffset(), getLength()));
-      copy.setReadOnly(!writable);
+      copy.setReadOnly(readOnly);
     }
 
     private int getLength() {
@@ -142,6 +143,7 @@ public class FragmentContent extends DiffContent {
       return myRangeMarker.getDocument();
     }
 
+    @NotNull
     @Override
     protected Document createCopy() {
       final Document originalDocument = myRangeMarker.getDocument();
diff --git a/platform/platform-api/src/com/intellij/openapi/diff/SimpleContent.java b/platform/platform-api/src/com/intellij/openapi/diff/SimpleContent.java
index b53de6217c67..55960fb8296e 100644
--- a/platform/platform-api/src/com/intellij/openapi/diff/SimpleContent.java
+++ b/platform/platform-api/src/com/intellij/openapi/diff/SimpleContent.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2012 JetBrains s.r.o.
+ * 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.
@@ -89,6 +89,7 @@ public class SimpleContent extends DiffContent {
     return myLineSeparators.restoreText(myDocument.getText());
   }
 
+  @Override
   public Document getDocument() {
     return myDocument;
   }
@@ -96,6 +97,7 @@ public class SimpleContent extends DiffContent {
   /**
    * @return null
    */
+  @Override
   public OpenFileDescriptor getOpenFileDescriptor(int offset) {
     return null;
   }
@@ -103,10 +105,12 @@ public class SimpleContent extends DiffContent {
   /**
    * @return null
    */
+  @Override
   public VirtualFile getFile() {
     return null;
   }
 
+  @Override
   @Nullable
   public FileType getContentType() {
     return myType;
@@ -115,6 +119,7 @@ public class SimpleContent extends DiffContent {
   /**
    * @return Encodes using default encoding
    */
+  @Override
   public byte[] getBytes() {
     String currentText = getText();
     if (myOriginalText.equals(myDocument.getText()) && myCharset == null) {
@@ -132,9 +137,7 @@ public class SimpleContent extends DiffContent {
       buffer.get(result, bomLength, encodedLength);
       return result;
     }
-    else {
-      return currentText.getBytes();
-    }
+    return currentText.getBytes();
   }
 
   @NotNull
@@ -154,7 +157,6 @@ public class SimpleContent extends DiffContent {
   /**
    * @param text     text of content
    * @param fileName used to determine content type
-   * @return
    */
   public static SimpleContent forFileContent(String text, String fileName) {
     FileType fileType;
@@ -212,7 +214,7 @@ public class SimpleContent extends DiffContent {
       LineTokenizer lineTokenizer = new LineTokenizer(text);
       String[] lines = lineTokenizer.execute();
       mySeparator = lineTokenizer.getLineSeparator();
-      LOG.assertTrue(mySeparator == null || mySeparator.length() > 0);
+      LOG.assertTrue(mySeparator == null || !mySeparator.isEmpty());
       if (mySeparator == null) mySeparator = SystemProperties.getLineSeparator();
       return LineTokenizer.concatLines(lines);
     }
diff --git a/platform/platform-impl/src/com/intellij/openapi/diff/impl/mergeTool/MergeRequestImpl.java b/platform/platform-impl/src/com/intellij/openapi/diff/impl/mergeTool/MergeRequestImpl.java
index b9a0fd3b9be8..1510183b8034 100644
--- a/platform/platform-impl/src/com/intellij/openapi/diff/impl/mergeTool/MergeRequestImpl.java
+++ b/platform/platform-impl/src/com/intellij/openapi/diff/impl/mergeTool/MergeRequestImpl.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2012 JetBrains s.r.o.
+ * 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.
@@ -89,14 +89,31 @@ public class MergeRequestImpl extends MergeRequest {
     myDiffContents[2] = right;
   }
 
+  @Override
   @NotNull
-  public DiffContent[] getContents() { return myDiffContents; }
+  public DiffContent[] getContents() {
+    return myDiffContents;
+  }
 
-  public String[] getContentTitles() { return myVersionTitles; }
-  public void setVersionTitles(String[] versionTitles) { myVersionTitles = versionTitles; }
+  @Override
+  public String[] getContentTitles() {
+    return myVersionTitles;
+  }
 
-  public String getWindowTitle() { return myWindowTitle; }
-  public void setWindowTitle(String windowTitle) { myWindowTitle = windowTitle; }
+  @Override
+  public void setVersionTitles(String[] versionTitles) {
+    myVersionTitles = versionTitles;
+  }
+
+  @Override
+  public String getWindowTitle() {
+    return myWindowTitle;
+  }
+
+  @Override
+  public void setWindowTitle(String windowTitle) {
+    myWindowTitle = windowTitle;
+  }
 
   public void setResult(int result) {
     if (result == DialogWrapper.OK_EXIT_CODE) applyChanges();
@@ -110,21 +127,26 @@ public class MergeRequestImpl extends MergeRequest {
     }
   }
 
-  public int getResult() { return myResult; }
+  @Override
+  public int getResult() {
+    return myResult;
+  }
 
   @Nullable
   private MergeContent getMergeContent() {
-    if (myDiffContents [1] instanceof MergeContent) {
+    if (myDiffContents[1] instanceof MergeContent) {
       return (MergeContent)myDiffContents[1];
     }
     return null;
   }
 
+  @Override
   @Nullable
   public DiffContent getResultContent() {
     return getMergeContent();
   }
 
+  @Override
   public void restoreOriginalContent() {
     final MergeContent mergeContent = getMergeContent();
     if (mergeContent == null) return;
@@ -163,6 +185,7 @@ public class MergeRequestImpl extends MergeRequest {
 
       configureAction(builder, builder.getOkAction(), myOkButtonPresentation);
       builder.setOkOperation(new Runnable() {
+        @Override
         public void run() {
           myOkButtonPresentation.run(builder.getDialogWrapper());
         }
@@ -176,6 +199,7 @@ public class MergeRequestImpl extends MergeRequest {
 
       configureAction(builder, builder.getCancelAction(), myCancelButtonPresentation);
       builder.setCancelOperation(new Runnable() {
+        @Override
         public void run() {
           myCancelButtonPresentation.run(builder.getDialogWrapper());
         }
@@ -191,6 +215,7 @@ public class MergeRequestImpl extends MergeRequest {
     return myHelpId;
   }
 
+  @Override
   public void setHelpId(@Nullable @NonNls String helpId) {
     myHelpId = helpId;
   }
@@ -211,23 +236,30 @@ public class MergeRequestImpl extends MergeRequest {
       myTarget.applyText(myWorkingDocument.getText(), myProject);
     }
 
-    public Document getDocument() { return myWorkingDocument; }
+    @Override
+    public Document getDocument() {
+      return myWorkingDocument;
+    }
 
+    @Override
     public OpenFileDescriptor getOpenFileDescriptor(int offset) {
       VirtualFile file = getFile();
       if (file == null) return null;
       return new OpenFileDescriptor(myProject, file, offset);
     }
 
+    @Override
     public VirtualFile getFile() {
       return myTarget.getFile();
     }
 
+    @Override
     @Nullable
     public FileType getContentType() {
       return myTarget.getContentType();
     }
 
+    @Override
     public byte[] getBytes() throws IOException {
       return myTarget.getBytes();
     }
@@ -250,6 +282,7 @@ public class MergeRequestImpl extends MergeRequest {
       changeCounter.addListener(this);
     }
 
+    @Override
     public void run() {
       if (myWasInvoked) return;
       if (!getWholePanel().isDisplayable()) return;
@@ -257,9 +290,9 @@ public class MergeRequestImpl extends MergeRequest {
       ChangeCounter.getOrCreate(myMergePanel.getMergeList()).removeListener(this);
       int doApply = Messages
         .showOkCancelDialog(getWholePanel(), DiffBundle.message("merge.all.changes.have.processed.save.and.finish.confirmation.text"),
-                    DiffBundle.message("all.changes.processed.dialog.title"),
-                    DiffBundle.message("merge.save.and.finish.button"), DiffBundle.message("merge.continue.button"),
-                    Messages.getQuestionIcon());
+                            DiffBundle.message("all.changes.processed.dialog.title"),
+                            DiffBundle.message("merge.save.and.finish.button"), DiffBundle.message("merge.continue.button"),
+                            Messages.getQuestionIcon());
       if (doApply != 0) return;
       myDialogWrapper.close(DialogWrapper.OK_EXIT_CODE);
     }
@@ -268,6 +301,7 @@ public class MergeRequestImpl extends MergeRequest {
       return myMergePanel.getComponent();
     }
 
+    @Override
     public void onCountersChanged(ChangeCounter counter) {
       if (myWasInvoked) return;
       if (counter.getChangeCounter() != 0 || counter.getConflictCounter() != 0) return;