diff --git a/platform/extensions/src/com/intellij/openapi/extensions/AreaListener.java b/platform/extensions/src/com/intellij/openapi/extensions/AreaListener.java
index 233e4ac2cd1e..a238636947cf 100644
--- a/platform/extensions/src/com/intellij/openapi/extensions/AreaListener.java
+++ b/platform/extensions/src/com/intellij/openapi/extensions/AreaListener.java
@@ -15,10 +15,12 @@
  */
 package com.intellij.openapi.extensions;
 
+import org.jetbrains.annotations.NotNull;
+
 /**
  * @author akireyev
  */
 public interface AreaListener {
-  void areaCreated(String areaClass, AreaInstance areaInstance);
-  void areaDisposing(String areaClass, AreaInstance areaInstance);
+  void areaCreated(@NotNull String areaClass, @NotNull AreaInstance areaInstance);
+  void areaDisposing(@NotNull String areaClass, @NotNull AreaInstance areaInstance);
 }
diff --git a/platform/extensions/src/com/intellij/openapi/extensions/ExtensionPoint.java b/platform/extensions/src/com/intellij/openapi/extensions/ExtensionPoint.java
index c019479b50d3..a992873032ee 100644
--- a/platform/extensions/src/com/intellij/openapi/extensions/ExtensionPoint.java
+++ b/platform/extensions/src/com/intellij/openapi/extensions/ExtensionPoint.java
@@ -52,6 +52,7 @@ public interface ExtensionPoint<T> {
 
   void reset();
 
+  @NotNull
   Class<T> getExtensionClass();
 
   @NotNull
diff --git a/platform/extensions/src/com/intellij/openapi/extensions/Extensions.java b/platform/extensions/src/com/intellij/openapi/extensions/Extensions.java
index 677affff6e31..80e3d022cd31 100644
--- a/platform/extensions/src/com/intellij/openapi/extensions/Extensions.java
+++ b/platform/extensions/src/com/intellij/openapi/extensions/Extensions.java
@@ -95,13 +95,13 @@ public class Extensions {
   @NotNull
   @SuppressWarnings({"unchecked"})
   public static <T> T[] getExtensions(@NotNull ExtensionPointName<T> extensionPointName) {
-    return (T[])getExtensions(extensionPointName.getName(), null);
+    return getExtensions(extensionPointName.getName(), null);
   }
 
   @NotNull
   @SuppressWarnings({"unchecked"})
   public static <T> T[] getExtensions(@NotNull ExtensionPointName<T> extensionPointName, AreaInstance areaInstance) {
-    return Extensions.<T>getExtensions(extensionPointName.getName(), areaInstance);
+    return getExtensions(extensionPointName.getName(), areaInstance);
   }
 
   @NotNull
@@ -133,20 +133,19 @@ public class Extensions {
     throw new IllegalArgumentException("could not find extension implementation " + extClass);
   }
 
-  public static void instantiateArea(@NonNls @NotNull String areaClass, @Nullable AreaInstance areaInstance, @Nullable AreaInstance parentAreaInstance) {
-    if (!ourAreaClass2Configuration.containsKey(areaClass)) {
+  public static void instantiateArea(@NonNls @NotNull String areaClass, @NotNull AreaInstance areaInstance, @Nullable AreaInstance parentAreaInstance) {
+    AreaClassConfiguration configuration = ourAreaClass2Configuration.get(areaClass);
+    if (configuration == null) {
       throw new IllegalArgumentException("Area class is not registered: " + areaClass);
     }
-    if (areaInstance == null || ourAreaInstance2area.containsKey(areaInstance)) {
-      throw new IllegalArgumentException("Area already instantiated for: " + areaInstance);
-    }
     ExtensionsArea parentArea = getArea(parentAreaInstance);
-    AreaClassConfiguration configuration = ourAreaClass2Configuration.get(areaClass);
     if (!equals(parentArea.getAreaClass(), configuration.getParentClassName())) {
       throw new IllegalArgumentException("Wrong parent area. Expected class: " + configuration.getParentClassName() + " actual class: " + parentArea.getAreaClass());
     }
     ExtensionsAreaImpl area = new ExtensionsAreaImpl(areaClass, areaInstance, parentArea.getPicoContainer(), ourLogger);
-    ourAreaInstance2area.put(areaInstance, area);
+    if (ourAreaInstance2area.put(areaInstance, area) != null) {
+      throw new IllegalArgumentException("Area already instantiated for: " + areaInstance);
+    }
     for (AreaListener listener : getAreaListeners()) {
       listener.areaCreated(areaClass, areaInstance);
     }
@@ -183,7 +182,8 @@ public class Extensions {
       for (AreaListener listener : getAreaListeners()) {
         listener.areaDisposing(areaClass, areaInstance);
       }
-    } finally {
+    }
+    finally {
       ourAreaInstance2area.remove(areaInstance);
     }
   }
@@ -200,11 +200,12 @@ public class Extensions {
     private final String myClassName;
     private final String myParentClassName;
 
-    AreaClassConfiguration(String className, String parentClassName) {
+    AreaClassConfiguration(@NotNull String className, String parentClassName) {
       myClassName = className;
       myParentClassName = parentClassName;
     }
 
+    @NotNull
     public String getClassName() {
       return myClassName;
     }
diff --git a/platform/extensions/src/com/intellij/openapi/extensions/impl/ExtensionPointImpl.java b/platform/extensions/src/com/intellij/openapi/extensions/impl/ExtensionPointImpl.java
index 44058e8516b1..9c6f782cbcc1 100644
--- a/platform/extensions/src/com/intellij/openapi/extensions/impl/ExtensionPointImpl.java
+++ b/platform/extensions/src/com/intellij/openapi/extensions/impl/ExtensionPointImpl.java
@@ -369,6 +369,7 @@ public class ExtensionPointImpl<T> implements ExtensionPoint<T> {
     }
   }
 
+  @NotNull
   @Override
   public Class<T> getExtensionClass() {
     // racy single-check: we don't care whether the access to 'myExtensionClass' is thread-safe
diff --git a/platform/extensions/src/com/intellij/openapi/extensions/impl/ExtensionsAreaImpl.java b/platform/extensions/src/com/intellij/openapi/extensions/impl/ExtensionsAreaImpl.java
index ee8f85f1a901..55be767a4d2a 100644
--- a/platform/extensions/src/com/intellij/openapi/extensions/impl/ExtensionsAreaImpl.java
+++ b/platform/extensions/src/com/intellij/openapi/extensions/impl/ExtensionsAreaImpl.java
@@ -69,8 +69,9 @@ public class ExtensionsAreaImpl implements ExtensionsArea {
     initialize();
   }
 
-  public ExtensionsAreaImpl(MutablePicoContainer picoContainer, LogProvider logger) {
-    this(null, null, picoContainer, logger);
+  @TestOnly
+  ExtensionsAreaImpl(MutablePicoContainer parentPicoContainer, @NotNull LogProvider logger) {
+    this(null, null, parentPicoContainer, logger);
   }
 
   @TestOnly
@@ -148,7 +149,7 @@ public class ExtensionsAreaImpl implements ExtensionsArea {
 
     ExtensionComponentAdapter adapter;
     final PicoContainer container = getPluginContainer(pluginId.getIdString());
-    final ExtensionPoint extensionPoint = getExtensionPoint(epName);
+    final ExtensionPointImpl extensionPoint = getExtensionPoint(epName);
     if (extensionPoint.getKind() == ExtensionPoint.Kind.INTERFACE) {
       String implClass = extensionElement.getAttributeValue("implementation");
       if (implClass == null) {
@@ -161,7 +162,7 @@ public class ExtensionsAreaImpl implements ExtensionsArea {
     }
     myExtensionElement2extension.put(extensionElement, adapter);
     internalGetPluginContainer().registerComponent(adapter);
-    getExtensionPoint(epName).registerExtensionAdapter(adapter);
+    extensionPoint.registerExtensionAdapter(adapter);
   }
 
   private static boolean shouldDeserializeInstance(Element extensionElement) {
diff --git a/platform/platform-impl/src/com/intellij/ide/plugins/IdeaPluginDescriptorImpl.java b/platform/platform-impl/src/com/intellij/ide/plugins/IdeaPluginDescriptorImpl.java
index 86f44b3528b5..23b7b0a3bbcf 100644
--- a/platform/platform-impl/src/com/intellij/ide/plugins/IdeaPluginDescriptorImpl.java
+++ b/platform/platform-impl/src/com/intellij/ide/plugins/IdeaPluginDescriptorImpl.java
@@ -252,14 +252,14 @@ public class IdeaPluginDescriptorImpl implements IdeaPluginDescriptor {
     if (myExtensions != null || myExtensionsPoints != null) {
       Extensions.getRootArea().getExtensionPoint(Extensions.AREA_LISTENER_EXTENSION_POINT).registerExtension(new AreaListener() {
         @Override
-        public void areaCreated(String areaClass, AreaInstance areaInstance) {
+        public void areaCreated(@NotNull String areaClass, @NotNull AreaInstance areaInstance) {
           if (PluginManager.shouldSkipPlugin(IdeaPluginDescriptorImpl.this)) return;
           final ExtensionsArea area = Extensions.getArea(areaInstance);
           area.registerAreaExtensionsAndPoints(IdeaPluginDescriptorImpl.this, myExtensionsPoints, myExtensions);
         }
 
         @Override
-        public void areaDisposing(String areaClass, AreaInstance areaInstance) {
+        public void areaDisposing(@NotNull String areaClass, @NotNull AreaInstance areaInstance) {
         }
       });
     }
diff --git a/platform/util/src/com/intellij/util/pico/DefaultPicoContainer.java b/platform/util/src/com/intellij/util/pico/DefaultPicoContainer.java
index c7dc592bb474..265582c0cbf1 100644
--- a/platform/util/src/com/intellij/util/pico/DefaultPicoContainer.java
+++ b/platform/util/src/com/intellij/util/pico/DefaultPicoContainer.java
@@ -49,6 +49,7 @@ public class DefaultPicoContainer implements MutablePicoContainer, Serializable
     this(new DefaultComponentAdapterFactory(), null);
   }
 
+  @Override
   public Collection<ComponentAdapter> getComponentAdapters() {
     return componentAdapters.getImmutableSet();
   }
@@ -62,6 +63,7 @@ public class DefaultPicoContainer implements MutablePicoContainer, Serializable
     return nonAssignableComponentAdapters.get().getReversedList();
   }
 
+  @Override
   @Nullable
   public final ComponentAdapter getComponentAdapter(Object componentKey) {
     ComponentAdapter adapter = getFromCache(componentKey);
@@ -84,6 +86,7 @@ public class DefaultPicoContainer implements MutablePicoContainer, Serializable
     return null;
   }
 
+  @Override
   @Nullable
   public ComponentAdapter getComponentAdapterOfType(Class componentType) {
     // See http://jira.codehaus.org/secure/ViewIssue.jspa?key=PICO-115
@@ -101,9 +104,7 @@ public class DefaultPicoContainer implements MutablePicoContainer, Serializable
       if (parent != null) {
         return parent.getComponentAdapterOfType(componentType);
       }
-      else {
-        return null;
-      }
+      return null;
     }
     else {
       Class[] foundClasses = new Class[found.size()];
@@ -115,6 +116,7 @@ public class DefaultPicoContainer implements MutablePicoContainer, Serializable
     }
   }
 
+  @Override
   public List getComponentAdaptersOfType(Class componentType) {
     if (componentType == null) {
       return Collections.emptyList();
@@ -130,6 +132,7 @@ public class DefaultPicoContainer implements MutablePicoContainer, Serializable
     return found;
   }
 
+  @Override
   public ComponentAdapter registerComponent(ComponentAdapter componentAdapter) {
     Object componentKey = componentAdapter.getComponentKey();
     if (componentKeyToAdapterCache.containsKey(componentKey)) {
@@ -156,6 +159,7 @@ public class DefaultPicoContainer implements MutablePicoContainer, Serializable
     return componentAdapter;
   }
 
+  @Override
   public ComponentAdapter unregisterComponent(Object componentKey) {
     ComponentAdapter adapter = componentKeyToAdapterCache.remove(componentKey);
 
@@ -171,10 +175,12 @@ public class DefaultPicoContainer implements MutablePicoContainer, Serializable
     }
   }
 
+  @Override
   public List getComponentInstances() throws PicoException {
     return getComponentInstancesOfType(Object.class);
   }
 
+  @Override
   public List getComponentInstancesOfType(Class componentType) {
     if (componentType == null) {
       return Collections.emptyList();
@@ -204,17 +210,14 @@ public class DefaultPicoContainer implements MutablePicoContainer, Serializable
     return result;
   }
 
+  @Override
   @Nullable
   public Object getComponentInstance(Object componentKey) {
     ComponentAdapter componentAdapter = getComponentAdapter(componentKey);
-    if (componentAdapter != null) {
-      return getInstance(componentAdapter);
-    }
-    else {
-      return null;
-    }
+    return componentAdapter == null ? null : getInstance(componentAdapter);
   }
 
+  @Override
   @Nullable
   public Object getComponentInstanceOfType(Class componentType) {
     final ComponentAdapter componentAdapter = getComponentAdapterOfType(componentType);
@@ -228,7 +231,7 @@ public class DefaultPicoContainer implements MutablePicoContainer, Serializable
     if (isLocal) {
       return getLocalInstance(componentAdapter);
     }
-    else if (parent != null) {
+    if (parent != null) {
       return parent.getComponentInstance(componentAdapter.getComponentKey());
     }
 
@@ -263,6 +266,7 @@ public class DefaultPicoContainer implements MutablePicoContainer, Serializable
   }
 
 
+  @Override
   @Nullable
   public ComponentAdapter unregisterComponentByInstance(Object componentInstance) {
     Collection<ComponentAdapter> adapters = getComponentAdapters();
@@ -276,36 +280,44 @@ public class DefaultPicoContainer implements MutablePicoContainer, Serializable
     return null;
   }
 
+  @Override
   public void verify() throws PicoVerificationException {
     new VerifyingVisitor().traverse(this);
   }
 
+  @Override
   public void start() {
     throw new UnsupportedOperationException();
   }
 
+  @Override
   public void stop() {
     throw new UnsupportedOperationException();
   }
 
+  @Override
   public void dispose() {
     throw new UnsupportedOperationException();
   }
 
+  @Override
   public MutablePicoContainer makeChildContainer() {
     DefaultPicoContainer pc = new DefaultPicoContainer(componentAdapterFactory, this);
     addChildContainer(pc);
     return pc;
   }
 
+  @Override
   public boolean addChildContainer(PicoContainer child) {
     return children.add(child);
   }
 
+  @Override
   public boolean removeChildContainer(PicoContainer child) {
     return children.remove(child);
   }
 
+  @Override
   public void accept(PicoVisitor visitor) {
     visitor.visitContainer(this);
     final List<ComponentAdapter> adapters = new ArrayList<ComponentAdapter>(getComponentAdapters());
@@ -318,27 +330,33 @@ public class DefaultPicoContainer implements MutablePicoContainer, Serializable
     }
   }
 
+  @Override
   public ComponentAdapter registerComponentInstance(@NotNull Object component) {
     return registerComponentInstance(component.getClass(), component);
   }
 
+  @Override
   public ComponentAdapter registerComponentInstance(@NotNull Object componentKey, @NotNull Object componentInstance) {
     return registerComponent(new InstanceComponentAdapter(componentKey, componentInstance));
   }
 
+  @Override
   public ComponentAdapter registerComponentImplementation(@NotNull Class componentImplementation) {
     return registerComponentImplementation(componentImplementation, componentImplementation);
   }
 
+  @Override
   public ComponentAdapter registerComponentImplementation(@NotNull Object componentKey, @NotNull Class componentImplementation) {
     return registerComponentImplementation(componentKey, componentImplementation, null);
   }
 
+  @Override
   public ComponentAdapter registerComponentImplementation(@NotNull Object componentKey, @NotNull Class componentImplementation, Parameter[] parameters) {
     ComponentAdapter componentAdapter = componentAdapterFactory.createComponentAdapter(componentKey, componentImplementation, parameters);
     return registerComponent(componentAdapter);
   }
 
+  @Override
   public PicoContainer getParent() {
     return parent;
   }