diff --git a/java/java-impl/src/com/intellij/psi/NonClasspathClassFinder.java b/java/java-impl/src/com/intellij/psi/NonClasspathClassFinder.java
index feb111e02e38..dd60aefb5a3e 100644
--- a/java/java-impl/src/com/intellij/psi/NonClasspathClassFinder.java
+++ b/java/java-impl/src/com/intellij/psi/NonClasspathClassFinder.java
@@ -31,18 +31,44 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.*;
+import java.util.concurrent.atomic.AtomicLong;
 
 /**
  * @author peter
  */
 public abstract class NonClasspathClassFinder extends PsiElementFinder {
   private static final Logger LOG = Logger.getInstance("#com.intellij.psi.NonClasspathClassFinder");
+  private final AtomicLong myLastStamp = new AtomicLong();
   protected final Project myProject;
+  private volatile List<VirtualFile> myCache;
 
   public NonClasspathClassFinder(Project project) {
     myProject = project;
   }
 
+  protected List<VirtualFile> getClassRoots() {
+    List<VirtualFile> cache = myCache;
+    long stamp = PsiManager.getInstance(myProject).getModificationTracker().getModificationCount();
+    if (myLastStamp.get() != stamp) {
+      cache = null;
+    }
+
+    if (cache != null && !cache.isEmpty()) {
+      for (VirtualFile file : cache) {
+        if (!file.isValid()) {
+          cache = null;
+          break;
+        }
+      }
+    }
+
+    if (cache == null) {
+      myCache = cache = calcClassRoots();
+      myLastStamp.set(stamp);
+    }
+    return cache;
+  }
+
   @Override
   public PsiClass findClass(@NotNull String qualifiedName, @NotNull GlobalSearchScope scope) {
     final List<VirtualFile> classRoots = getClassRoots();
@@ -71,7 +97,7 @@ public abstract class NonClasspathClassFinder extends PsiElementFinder {
     return null;
   }
 
-  protected abstract List<VirtualFile> getClassRoots();
+  protected abstract List<VirtualFile> calcClassRoots();
 
   @NotNull
   @Override
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/gant/GantClassFinder.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/gant/GantClassFinder.java
index 4496fb1afa95..6d2e0105aac3 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/gant/GantClassFinder.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/gant/GantClassFinder.java
@@ -33,7 +33,7 @@ public class GantClassFinder extends NonClasspathClassFinder {
   }
 
   @Override
-  protected List<VirtualFile> getClassRoots() {
+  protected List<VirtualFile> calcClassRoots() {
     return mySettings.getClassRoots();
   }
 
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/gant/GantSettings.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/gant/GantSettings.java
index e2f46ad52ccb..2af617fd06d5 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/gant/GantSettings.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/gant/GantSettings.java
@@ -33,6 +33,9 @@ import org.jetbrains.plugins.groovy.util.SdkHomeSettings;
     }
 )
 public class GantSettings extends SdkHomeSettings {
+  public GantSettings(Project project) {
+    super(project);
+  }
 
   public static GantSettings getInstance(Project project) {
     return ServiceManager.getService(project, GantSettings.class);
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/gradle/GradleClassFinder.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/gradle/GradleClassFinder.java
index d30ec8b12fc6..39b3168b0322 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/gradle/GradleClassFinder.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/gradle/GradleClassFinder.java
@@ -34,7 +34,7 @@ public class GradleClassFinder extends NonClasspathClassFinder {
   }
 
   @Override
-  protected List<VirtualFile> getClassRoots() {
+  protected List<VirtualFile> calcClassRoots() {
     return mySettings.getClassRoots();
   }
 
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/gradle/GradleSettings.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/gradle/GradleSettings.java
index 15f8b7e5f29f..d897bf33dca4 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/gradle/GradleSettings.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/gradle/GradleSettings.java
@@ -33,6 +33,9 @@ import org.jetbrains.plugins.groovy.util.SdkHomeSettings;
     }
 )
 public class GradleSettings extends SdkHomeSettings {
+  public GradleSettings(Project project) {
+    super(project);
+  }
 
   public static GradleSettings getInstance(Project project) {
     return ServiceManager.getService(project, GradleSettings.class);
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/util/SdkHomeSettings.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/util/SdkHomeSettings.java
index 2ec1dd20b9af..22302709e669 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/util/SdkHomeSettings.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/util/SdkHomeSettings.java
@@ -16,11 +16,14 @@
 
 package org.jetbrains.plugins.groovy.util;
 
+import com.intellij.openapi.components.PersistentStateComponent;
+import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.openapi.vfs.JarFileSystem;
 import com.intellij.openapi.vfs.LocalFileSystem;
 import com.intellij.openapi.vfs.VirtualFile;
-import com.intellij.openapi.components.PersistentStateComponent;
+import com.intellij.psi.PsiManager;
+import com.intellij.psi.impl.PsiModificationTrackerImpl;
 import com.intellij.util.containers.ContainerUtil;
 import org.jetbrains.annotations.Nullable;
 
@@ -32,9 +35,12 @@ import java.util.List;
  * @author peter
  */
 public abstract class SdkHomeSettings implements PersistentStateComponent<SdkHomeConfigurable.SdkHomeBean> {
+  private final PsiModificationTrackerImpl myTracker;
   private SdkHomeConfigurable.SdkHomeBean mySdkPath;
-  private volatile VirtualFile mySdkHome;
-  private volatile List<VirtualFile> myClassRoots;
+
+  protected SdkHomeSettings(Project project) {
+    myTracker = (PsiModificationTrackerImpl)PsiManager.getInstance(project).getModificationTracker();
+  }
 
   public SdkHomeConfigurable.SdkHomeBean getState() {
     return mySdkPath;
@@ -42,16 +48,7 @@ public abstract class SdkHomeSettings implements PersistentStateComponent<SdkHom
 
   public void loadState(SdkHomeConfigurable.SdkHomeBean state) {
     mySdkPath = state;
-    myClassRoots = null;
-    mySdkHome = null;
-  }
-
-  private synchronized void calculateRoots() {
-    if (myClassRoots != null) {
-      return;
-    }
-    mySdkHome = calcHome(mySdkPath);
-    myClassRoots = calcRoots(mySdkHome);
+    myTracker.incCounter();
   }
 
   @Nullable
@@ -70,17 +67,11 @@ public abstract class SdkHomeSettings implements PersistentStateComponent<SdkHom
 
   @Nullable
   public VirtualFile getSdkHome() {
-    if (myClassRoots == null) {
-      calculateRoots();
-    }
-    return mySdkHome;
+    return calcHome(mySdkPath);
   }
 
   public List<VirtualFile> getClassRoots() {
-    if (myClassRoots == null) {
-      calculateRoots();
-    }
-    return myClassRoots;
+    return calcRoots(getSdkHome());
   }
 
   private static List<VirtualFile> calcRoots(@Nullable VirtualFile home) {