diff --git a/platform/core-api/src/com/intellij/util/CharTable.java b/platform/core-api/src/com/intellij/util/CharTable.java
index 98c869bfc277..933db89e11da 100644
--- a/platform/core-api/src/com/intellij/util/CharTable.java
+++ b/platform/core-api/src/com/intellij/util/CharTable.java
@@ -16,6 +16,7 @@
 package com.intellij.util;
 
 import com.intellij.openapi.util.Key;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * @author ik
@@ -23,7 +24,9 @@ import com.intellij.openapi.util.Key;
 public interface CharTable {
   Key<CharTable> CHAR_TABLE_KEY = new Key<CharTable>("Char table");
 
-  CharSequence intern(CharSequence text);
+  @NotNull
+  CharSequence intern(@NotNull CharSequence text);
 
-  CharSequence intern(CharSequence baseText, int startOffset, int endOffset);
+  @NotNull
+  CharSequence intern(@NotNull CharSequence baseText, int startOffset, int endOffset);
 }
diff --git a/platform/core-impl/src/com/intellij/psi/impl/source/IdentityCharTable.java b/platform/core-impl/src/com/intellij/psi/impl/source/IdentityCharTable.java
index 5864a34a19dd..2d05ee127bd1 100644
--- a/platform/core-impl/src/com/intellij/psi/impl/source/IdentityCharTable.java
+++ b/platform/core-impl/src/com/intellij/psi/impl/source/IdentityCharTable.java
@@ -17,6 +17,7 @@
 package com.intellij.psi.impl.source;
 
 import com.intellij.util.CharTable;
+import org.jetbrains.annotations.NotNull;
 
 /*
  * User: max
@@ -27,13 +28,15 @@ public class IdentityCharTable implements CharTable {
 
   public static final IdentityCharTable INSTANCE = new IdentityCharTable();
 
+  @NotNull
   @Override
-  public CharSequence intern(final CharSequence text) {
+  public CharSequence intern(@NotNull final CharSequence text) {
     return text;
   }
 
+  @NotNull
   @Override
-  public CharSequence intern(CharSequence baseText, int startOffset, int endOffset) {
+  public CharSequence intern(@NotNull CharSequence baseText, int startOffset, int endOffset) {
     if (endOffset - startOffset == baseText.length()) return baseText.toString();
     return baseText.subSequence(startOffset, endOffset);
   }
diff --git a/platform/util/src/com/intellij/openapi/util/JDOMUtil.java b/platform/util/src/com/intellij/openapi/util/JDOMUtil.java
index 5ce3bae01fe5..f14d7e5abcf9 100644
--- a/platform/util/src/com/intellij/openapi/util/JDOMUtil.java
+++ b/platform/util/src/com/intellij/openapi/util/JDOMUtil.java
@@ -179,7 +179,7 @@ public class JDOMUtil {
     }
   }
 
-  public static void internElement(final Element element, final StringInterner interner) {
+  public static void internElement(@NotNull Element element, @NotNull StringInterner interner) {
     element.setName(intern(interner, element.getName()));
 
     final List attributes = element.getAttributes();
diff --git a/platform/util/src/com/intellij/openapi/util/text/StringUtil.java b/platform/util/src/com/intellij/openapi/util/text/StringUtil.java
index 85085a37f17e..ebf1ce7c5580 100644
--- a/platform/util/src/com/intellij/openapi/util/text/StringUtil.java
+++ b/platform/util/src/com/intellij/openapi/util/text/StringUtil.java
@@ -1935,10 +1935,12 @@ public class StringUtil extends StringUtilRt {
     if (v1 == null && v2 == null) {
       return 0;
     }
-    else if (v1 == null) {
+    if (v1 == null) {
       return -1;
     }
-    else if (v2 == null) return 1;
+    if (v2 == null) {
+      return 1;
+    }
 
     String[] part1 = v1.split("[\\.\\_\\-]");
     String[] part2 = v2.split("[\\.\\_\\-]");
diff --git a/platform/util/src/com/intellij/util/containers/MultiMap.java b/platform/util/src/com/intellij/util/containers/MultiMap.java
index e45e4924b94f..ec9c0f5cb0c3 100644
--- a/platform/util/src/com/intellij/util/containers/MultiMap.java
+++ b/platform/util/src/com/intellij/util/containers/MultiMap.java
@@ -28,7 +28,6 @@ import java.util.*;
  * @author Dmitry Avdeev
  */
 public class MultiMap<K, V> implements Serializable {
-
   public static final MultiMap EMPTY = new MultiMap() {
     @Override
     protected Map createMap() {
@@ -156,11 +155,12 @@ public class MultiMap<K, V> implements Serializable {
   public Collection<? extends V> values() {
     if (values == null) {
       values = new AbstractCollection<V>() {
+        @NotNull
         @Override
         public Iterator<V> iterator() {
           return new Iterator<V>() {
 
-            private Iterator<Collection<V>> mapIterator = myMap.values().iterator();
+            private final Iterator<Collection<V>> mapIterator = myMap.values().iterator();
 
             private Iterator<V> itr = EmptyIterator.getInstance();
 
diff --git a/platform/util/src/com/intellij/util/text/CharArrayCharSequence.java b/platform/util/src/com/intellij/util/text/CharArrayCharSequence.java
index c833a2d5d80d..676aeea402a4 100644
--- a/platform/util/src/com/intellij/util/text/CharArrayCharSequence.java
+++ b/platform/util/src/com/intellij/util/text/CharArrayCharSequence.java
@@ -53,6 +53,8 @@ public class CharArrayCharSequence implements CharSequenceBackedByArray {
     return start == 0 && end == length() ? this : new CharArrayCharSequence(myChars, myStart + start, myStart + end);
   }
 
+  @Override
+  @NotNull
   public String toString() {
     return new String(myChars, myStart, myEnd - myStart); //TODO StringFactory
   }
@@ -66,6 +68,7 @@ public class CharArrayCharSequence implements CharSequenceBackedByArray {
     return chars;
   }
 
+  @Override
   public int hashCode() {
     return StringUtil.stringHashCode(myChars, myStart, myEnd);
   }