diff --git a/java/java-tests/testSrc/com/intellij/java/psi/ModifyAnnotationsTest.java b/java/java-tests/testSrc/com/intellij/java/psi/ModifyAnnotationsTest.java
index 552a7656e192..b70c66665c5e 100644
--- a/java/java-tests/testSrc/com/intellij/java/psi/ModifyAnnotationsTest.java
+++ b/java/java-tests/testSrc/com/intellij/java/psi/ModifyAnnotationsTest.java
@@ -37,7 +37,7 @@ public class ModifyAnnotationsTest extends PsiTestCase {
     super.setUp();
 
     String root = JavaTestUtil.getJavaTestDataPath() + "/psi/repositoryUse/modifyAnnotations";
-    PsiTestUtil.removeAllRoots(myModule, IdeaTestUtil.getMockJdk17("mock 1.5"));
+    PsiTestUtil.removeAllRoots(myModule, IdeaTestUtil.getMockJdk17());
     PsiTestUtil.createTestProjectStructure(myProject, myModule, root, myFilesToDelete);
   }
 
diff --git a/java/java-tests/testSrc/com/intellij/java/psi/Src15RepositoryUseTest.java b/java/java-tests/testSrc/com/intellij/java/psi/Src15RepositoryUseTest.java
index bdf1464cd06b..358de60e8fee 100644
--- a/java/java-tests/testSrc/com/intellij/java/psi/Src15RepositoryUseTest.java
+++ b/java/java-tests/testSrc/com/intellij/java/psi/Src15RepositoryUseTest.java
@@ -49,7 +49,7 @@ public class Src15RepositoryUseTest extends PsiTestCase {
 
     LanguageLevelProjectExtension.getInstance(myProject).setLanguageLevel(LanguageLevel.JDK_1_5);
     String root = PathManagerEx.getTestDataPath() + "/psi/repositoryUse/src15";
-    PsiTestUtil.removeAllRoots(myModule, IdeaTestUtil.getMockJdk17("mock 1.5"));
+    PsiTestUtil.removeAllRoots(myModule, IdeaTestUtil.getMockJdk17());
     PsiTestUtil.createTestProjectStructure(myProject, myModule, root, myFilesToDelete);
   }
 
diff --git a/java/java-tests/testSrc/com/intellij/java/psi/search/FindUsages15Test.java b/java/java-tests/testSrc/com/intellij/java/psi/search/FindUsages15Test.java
index 84aedb0e6744..3040ced85216 100644
--- a/java/java-tests/testSrc/com/intellij/java/psi/search/FindUsages15Test.java
+++ b/java/java-tests/testSrc/com/intellij/java/psi/search/FindUsages15Test.java
@@ -36,7 +36,7 @@ public class FindUsages15Test extends PsiTestCase{
 
     LanguageLevelProjectExtension.getInstance(myJavaFacade.getProject()).setLanguageLevel(LanguageLevel.JDK_1_5);
     String root = JavaTestUtil.getJavaTestDataPath() + "/psi/search/findUsages15/" + getTestName(true);
-    PsiTestUtil.removeAllRoots(myModule, IdeaTestUtil.getMockJdk17("java 1.5"));
+    PsiTestUtil.removeAllRoots(myModule, IdeaTestUtil.getMockJdk17());
     PsiTestUtil.createTestProjectStructure(myProject, myModule, root, myFilesToDelete);
   }
 
diff --git a/java/java-tests/testSrc/com/intellij/java/refactoring/CopyClassTest.java b/java/java-tests/testSrc/com/intellij/java/refactoring/CopyClassTest.java
index 36561ab6b5f7..a6ec2ed3490c 100644
--- a/java/java-tests/testSrc/com/intellij/java/refactoring/CopyClassTest.java
+++ b/java/java-tests/testSrc/com/intellij/java/refactoring/CopyClassTest.java
@@ -67,7 +67,7 @@ public class CopyClassTest extends CodeInsightTestCase {
   private void doTest(final String oldName, final String copyName) throws Exception {
     String root = JavaTestUtil.getJavaTestDataPath() + "/refactoring/copyClass/" + getTestName(true);
 
-    PsiTestUtil.removeAllRoots(myModule, IdeaTestUtil.getMockJdk17("java 1.5"));
+    PsiTestUtil.removeAllRoots(myModule, IdeaTestUtil.getMockJdk17());
     myRootDir = PsiTestUtil.createTestProjectStructure(myProject, myModule, root, myFilesToDelete);
 
     performAction(oldName, copyName);
diff --git a/java/java-tests/testSrc/com/intellij/roots/InheritedJdkTest.java b/java/java-tests/testSrc/com/intellij/roots/InheritedJdkTest.java
index 8bf94166f3f4..843387173b8a 100644
--- a/java/java-tests/testSrc/com/intellij/roots/InheritedJdkTest.java
+++ b/java/java-tests/testSrc/com/intellij/roots/InheritedJdkTest.java
@@ -37,7 +37,7 @@ public class InheritedJdkTest extends ModuleTestCase {
   }
 
   public void test1() {
-    final Sdk jdk = IdeaTestUtil.getMockJdk17("java 1.4");
+    final Sdk jdk = IdeaTestUtil.getMockJdk17();
     ApplicationManager.getApplication().runWriteAction(() -> ProjectJdkTable.getInstance().addJdk(jdk));
     final ModuleRootManager rootManager = ModuleRootManager.getInstance(myModule);
 
@@ -55,7 +55,7 @@ public class InheritedJdkTest extends ModuleTestCase {
     assertFalse("JDK is not inherited after setJdk(null)", rootManager.isSdkInherited());
     assertNull("No JDK assigned", rootManager.getSdk());
 
-    final Sdk jdk1 = IdeaTestUtil.getMockJdk17("jjj");
+    final Sdk jdk1 = IdeaTestUtil.getMockJdk17();
     ApplicationManager.getApplication().runWriteAction(() -> ProjectJdkTable.getInstance().addJdk(jdk1));
     ModuleRootModificationUtil.setModuleSdk(myModule, jdk1);
 
diff --git a/platform/core-api/src/com/intellij/openapi/vfs/JarCopyingFileSystem.java b/platform/core-api/src/com/intellij/openapi/vfs/JarCopyingFileSystem.java
index 768884a2194e..5e77cb221b65 100644
--- a/platform/core-api/src/com/intellij/openapi/vfs/JarCopyingFileSystem.java
+++ b/platform/core-api/src/com/intellij/openapi/vfs/JarCopyingFileSystem.java
@@ -15,9 +15,11 @@
  */
 package com.intellij.openapi.vfs;
 
+import org.jetbrains.annotations.NotNull;
+
 /**
  * @author yole
  */
 public interface JarCopyingFileSystem {
-  void setNoCopyJarForPath(String pathInJar);
+  void setNoCopyJarForPath(@NotNull String pathInJar);
 }
diff --git a/platform/external-system-impl/testSrc/com/intellij/openapi/externalSystem/test/ExternalSystemTestCase.java b/platform/external-system-impl/testSrc/com/intellij/openapi/externalSystem/test/ExternalSystemTestCase.java
index f701668a9e25..0f657a5e3f9c 100644
--- a/platform/external-system-impl/testSrc/com/intellij/openapi/externalSystem/test/ExternalSystemTestCase.java
+++ b/platform/external-system-impl/testSrc/com/intellij/openapi/externalSystem/test/ExternalSystemTestCase.java
@@ -455,13 +455,13 @@ public abstract class ExternalSystemTestCase extends UsefulTestCase {
   }
 
   protected Sdk setupJdkForModule(final String moduleName) {
-    final Sdk sdk = true ? JavaAwareProjectJdkTableImpl.getInstanceEx().getInternalJdk() : createJdk("Java 1.5");
+    final Sdk sdk = true ? JavaAwareProjectJdkTableImpl.getInstanceEx().getInternalJdk() : createJdk();
     ModuleRootModificationUtil.setModuleSdk(getModule(moduleName), sdk);
     return sdk;
   }
 
-  protected static Sdk createJdk(String versionName) {
-    return IdeaTestUtil.getMockJdk17(versionName);
+  protected static Sdk createJdk() {
+    return IdeaTestUtil.getMockJdk17();
   }
 
   protected Module getModule(final String name) {
diff --git a/platform/platform-impl/src/com/intellij/openapi/vfs/impl/jar/JarFileSystemImpl.java b/platform/platform-impl/src/com/intellij/openapi/vfs/impl/jar/JarFileSystemImpl.java
index fc44806adf50..4846e3294336 100644
--- a/platform/platform-impl/src/com/intellij/openapi/vfs/impl/jar/JarFileSystemImpl.java
+++ b/platform/platform-impl/src/com/intellij/openapi/vfs/impl/jar/JarFileSystemImpl.java
@@ -48,8 +48,8 @@ public class JarFileSystemImpl extends JarFileSystem {
   }
 
   @Override
-  public void setNoCopyJarForPath(String pathInJar) {
-    if (myNoCopyJarPaths == null || pathInJar == null) return;
+  public void setNoCopyJarForPath(@NotNull String pathInJar) {
+    if (myNoCopyJarPaths == null) return;
     int index = pathInJar.indexOf(JAR_SEPARATOR);
     if (index < 0) return;
     String path = FileUtil.toSystemIndependentName(pathInJar.substring(0, index));
diff --git a/platform/projectModel-api/src/com/intellij/openapi/projectRoots/SdkModificator.java b/platform/projectModel-api/src/com/intellij/openapi/projectRoots/SdkModificator.java
index dd8672c27c9b..8d99455741f0 100644
--- a/platform/projectModel-api/src/com/intellij/openapi/projectRoots/SdkModificator.java
+++ b/platform/projectModel-api/src/com/intellij/openapi/projectRoots/SdkModificator.java
@@ -39,7 +39,7 @@ public interface SdkModificator {
   void setSdkAdditionalData(SdkAdditionalData data);
 
   @NotNull
-  VirtualFile[] getRoots(OrderRootType rootType);
+  VirtualFile[] getRoots(@NotNull OrderRootType rootType);
 
   void addRoot(@NotNull VirtualFile root, @NotNull OrderRootType rootType);
 
diff --git a/platform/projectModel-api/src/com/intellij/openapi/roots/PersistentOrderRootType.java b/platform/projectModel-api/src/com/intellij/openapi/roots/PersistentOrderRootType.java
index cb8f90e35326..2c76d08f76be 100644
--- a/platform/projectModel-api/src/com/intellij/openapi/roots/PersistentOrderRootType.java
+++ b/platform/projectModel-api/src/com/intellij/openapi/roots/PersistentOrderRootType.java
@@ -28,7 +28,7 @@ public class PersistentOrderRootType extends OrderRootType {
   private final String myModulePathsName;
   private final String myOldSdkRootName;
 
-  protected PersistentOrderRootType(@NonNls String name, @NonNls @Nullable String sdkRootName, @NonNls @Nullable String modulePathsName, @NonNls final @Nullable String oldSdkRootName) {
+  protected PersistentOrderRootType(@NonNls String name, @NonNls @Nullable String sdkRootName, @NonNls @Nullable String modulePathsName, @Nullable @NonNls final String oldSdkRootName) {
     super(name);
     mySdkRootName = sdkRootName;
     myModulePathsName = modulePathsName;
diff --git a/platform/projectModel-api/src/com/intellij/openapi/roots/ex/ProjectRootManagerEx.java b/platform/projectModel-api/src/com/intellij/openapi/roots/ex/ProjectRootManagerEx.java
index 9358d9242449..f804480d589d 100644
--- a/platform/projectModel-api/src/com/intellij/openapi/roots/ex/ProjectRootManagerEx.java
+++ b/platform/projectModel-api/src/com/intellij/openapi/roots/ex/ProjectRootManagerEx.java
@@ -26,9 +26,9 @@ public abstract class ProjectRootManagerEx extends ProjectRootManager {
     return (ProjectRootManagerEx)getInstance(project);
   }
 
-  public abstract void addProjectJdkListener(ProjectJdkListener listener);
+  public abstract void addProjectJdkListener(@NotNull ProjectJdkListener listener);
 
-  public abstract void removeProjectJdkListener(ProjectJdkListener listener);
+  public abstract void removeProjectJdkListener(@NotNull ProjectJdkListener listener);
 
   // invokes runnable surrounded by beforeRootsChange()/rootsChanged() callbacks
   public abstract void makeRootsChange(@NotNull Runnable runnable, boolean fileTypes, boolean fireEvents);
@@ -41,6 +41,7 @@ public abstract class ProjectRootManagerEx extends ProjectRootManager {
    * @see ProjectRootManagerEx#addProjectJdkListener(ProjectJdkListener)
    * @see ProjectRootManagerEx#removeProjectJdkListener(ProjectJdkListener)
    */
+  @FunctionalInterface
   public interface ProjectJdkListener extends EventListener {
     void projectJdkChanged();
   }
diff --git a/platform/projectModel-impl/src/com/intellij/openapi/roots/impl/LibraryOrderEntryBaseImpl.java b/platform/projectModel-impl/src/com/intellij/openapi/roots/impl/LibraryOrderEntryBaseImpl.java
index 08fb18147812..c6cbc8b60021 100644
--- a/platform/projectModel-impl/src/com/intellij/openapi/roots/impl/LibraryOrderEntryBaseImpl.java
+++ b/platform/projectModel-impl/src/com/intellij/openapi/roots/impl/LibraryOrderEntryBaseImpl.java
@@ -32,7 +32,7 @@ import org.jetbrains.annotations.Nullable;
  */
 abstract class LibraryOrderEntryBaseImpl extends OrderEntryBaseImpl implements LibraryOrSdkOrderEntry {
   private static final Logger LOG = Logger.getInstance("#com.intellij.openapi.roots.impl.LibraryOrderEntryBaseImpl");
-  protected final ProjectRootManagerImpl myProjectRootManagerImpl;
+  final ProjectRootManagerImpl myProjectRootManagerImpl;
   @NotNull protected DependencyScope myScope = DependencyScope.COMPILE;
   @Nullable private RootProvider myCurrentlySubscribedRootProvider;
 
@@ -81,7 +81,7 @@ abstract class LibraryOrderEntryBaseImpl extends OrderEntryBaseImpl implements L
     return getRootModel().getModule();
   }
 
-  protected void updateFromRootProviderAndSubscribe() {
+  void updateFromRootProviderAndSubscribe() {
     getRootModel().makeExternalChange(() -> resubscribe(getRootProvider()));
   }
 
diff --git a/plugins/maven/src/test/java/org/jetbrains/idea/maven/MavenImportingTestCase.java b/plugins/maven/src/test/java/org/jetbrains/idea/maven/MavenImportingTestCase.java
index 8c8eb1aa6a9a..43f7329ca396 100644
--- a/plugins/maven/src/test/java/org/jetbrains/idea/maven/MavenImportingTestCase.java
+++ b/plugins/maven/src/test/java/org/jetbrains/idea/maven/MavenImportingTestCase.java
@@ -532,8 +532,8 @@ public abstract class MavenImportingTestCase extends MavenTestCase {
     return sdk;
   }
 
-  protected static Sdk createJdk(String versionName) {
-    return IdeaTestUtil.getMockJdk17(versionName);
+  protected static Sdk createJdk() {
+    return IdeaTestUtil.getMockJdk17();
   }
 
   protected static AtomicInteger configConfirmationForYesAnswer() {
diff --git a/plugins/maven/src/test/java/org/jetbrains/idea/maven/execution/MavenResolveToWorkspaceTest.java b/plugins/maven/src/test/java/org/jetbrains/idea/maven/execution/MavenResolveToWorkspaceTest.java
index 121bb7f89a60..19d268d8c9fc 100644
--- a/plugins/maven/src/test/java/org/jetbrains/idea/maven/execution/MavenResolveToWorkspaceTest.java
+++ b/plugins/maven/src/test/java/org/jetbrains/idea/maven/execution/MavenResolveToWorkspaceTest.java
@@ -79,7 +79,7 @@ public abstract class MavenResolveToWorkspaceTest extends MavenImportingTestCase
 
     //assertModules("project", "moduleA", "moduleB");
 
-    WriteAction.run(() -> ProjectRootManager.getInstance(myProject).setProjectSdk(createJdk("Java 1.5")));
+    WriteAction.run(() -> ProjectRootManager.getInstance(myProject).setProjectSdk(createJdk()));
 
     MavenRunnerParameters runnerParameters = new MavenRunnerParameters(moduleB.getParent().getPath(), false, Collections.singletonList("jetty:run"), Collections.emptyMap());
     runnerParameters.setResolveToWorkspace(true);
diff --git a/plugins/maven/src/test/java/org/jetbrains/idea/maven/importing/MavenModuleBuilderTest.java b/plugins/maven/src/test/java/org/jetbrains/idea/maven/importing/MavenModuleBuilderTest.java
index f0dd740a5505..17b550a14dc4 100644
--- a/plugins/maven/src/test/java/org/jetbrains/idea/maven/importing/MavenModuleBuilderTest.java
+++ b/plugins/maven/src/test/java/org/jetbrains/idea/maven/importing/MavenModuleBuilderTest.java
@@ -41,7 +41,7 @@ public class MavenModuleBuilderTest extends MavenImportingTestCase {
     super.setUp();
     myBuilder = new MavenModuleBuilder();
 
-    createJdk("Java 1.5");
+    createJdk();
     setModuleNameAndRoot("module", getProjectPath());
   }