diff --git a/src/main/java/org/jastadd/tooling/JastAddIcons.java b/src/main/java/org/jastadd/tooling/JastAddIcons.java
index 38df87c5cee0aeac53834e0738635e0ceb897a4c..011ca9980e71c02eb890798de3fb76077e169ae1 100644
--- a/src/main/java/org/jastadd/tooling/JastAddIcons.java
+++ b/src/main/java/org/jastadd/tooling/JastAddIcons.java
@@ -6,10 +6,10 @@ import javax.swing.*;
 
 public class JastAddIcons {
 
+  public static final Icon FILE = IconLoader.getIcon("/icons/jastadd.svg", JastAddIcons.class);
+
   private JastAddIcons() {
     throw new IllegalStateException("Utility class");
   }
 
-  public static final Icon FILE = IconLoader.getIcon("/icons/jastadd.svg", JastAddIcons.class);
-
 }
diff --git a/src/main/java/org/jastadd/tooling/RelAstGrammar.java b/src/main/java/org/jastadd/tooling/RelAstGrammar.java
index 0aafd2597c60b93c823fdb7e3b8d0106418ddd59..2b6f58f75be1d4eeb5e6c50133dc59b66b1686e7 100644
--- a/src/main/java/org/jastadd/tooling/RelAstGrammar.java
+++ b/src/main/java/org/jastadd/tooling/RelAstGrammar.java
@@ -1,16 +1,13 @@
 package org.jastadd.tooling;
 
-
 import com.intellij.lang.Language;
 
 public class RelAstGrammar extends Language {
 
+  public static final RelAstGrammar INSTANCE = new RelAstGrammar();
 
-    public static final RelAstGrammar INSTANCE = new RelAstGrammar();
-
-    private RelAstGrammar() {
-      super("JastAddGrammar");
-    }
-
+  private RelAstGrammar() {
+    super("JastAddGrammar");
+  }
 
 }
diff --git a/src/main/java/org/jastadd/tooling/RelAstGrammarColorSettingsPage.java b/src/main/java/org/jastadd/tooling/RelAstGrammarColorSettingsPage.java
index bb980d4b616ea414d7a8a808b78c3613ad212326..8acc9f5fdf5d2ce29ca42adb9bfd320fdcfd32c4 100644
--- a/src/main/java/org/jastadd/tooling/RelAstGrammarColorSettingsPage.java
+++ b/src/main/java/org/jastadd/tooling/RelAstGrammarColorSettingsPage.java
@@ -68,13 +68,13 @@ public class RelAstGrammarColorSettingsPage implements ColorSettingsPage {
 
   @NotNull
   @Override
-  public AttributesDescriptor[] getAttributeDescriptors() {
+  public AttributesDescriptor @NotNull [] getAttributeDescriptors() {
     return DESCRIPTORS;
   }
 
   @NotNull
   @Override
-  public ColorDescriptor[] getColorDescriptors() {
+  public ColorDescriptor @NotNull [] getColorDescriptors() {
     return ColorDescriptor.EMPTY_ARRAY;
   }
 
diff --git a/src/main/java/org/jastadd/tooling/RelAstGrammarFileType.java b/src/main/java/org/jastadd/tooling/RelAstGrammarFileType.java
index 3d00b9748aea3fea5322cfb42fbdfaf92a92a08a..793a3a47b9c5a247ad0240379ae75c0e564a9b91 100644
--- a/src/main/java/org/jastadd/tooling/RelAstGrammarFileType.java
+++ b/src/main/java/org/jastadd/tooling/RelAstGrammarFileType.java
@@ -33,7 +33,6 @@ public class RelAstGrammarFileType extends LanguageFileType {
   }
 
 
-
   @Nullable
   @Override
   public Icon getIcon() {
diff --git a/src/main/java/org/jastadd/tooling/RelAstGrammarReferenceContributor.java b/src/main/java/org/jastadd/tooling/RelAstGrammarReferenceContributor.java
index c302968f251a32de7a41d1f13daee492e243db00..326b07524fa33af52382a98d2764d9fea1ba60fa 100644
--- a/src/main/java/org/jastadd/tooling/RelAstGrammarReferenceContributor.java
+++ b/src/main/java/org/jastadd/tooling/RelAstGrammarReferenceContributor.java
@@ -15,8 +15,8 @@ public class RelAstGrammarReferenceContributor extends PsiReferenceContributor {
       new PsiReferenceProvider() {
         @NotNull
         @Override
-        public PsiReference[] getReferencesByElement(@NotNull PsiElement element,
-                                                     @NotNull ProcessingContext context) {
+        public PsiReference @NotNull [] getReferencesByElement(@NotNull PsiElement element,
+                                                               @NotNull ProcessingContext context) {
 
           RelAstGrammarTypeReference typeReference = (RelAstGrammarTypeReference) element;
           String value = typeReference.getText();
diff --git a/src/main/java/org/jastadd/tooling/RelAstGrammarSyntaxHighlighter.java b/src/main/java/org/jastadd/tooling/RelAstGrammarSyntaxHighlighter.java
index fad48b51826737b77d6083c010314e5843b73de5..23bc610ade194ee4c891a330d97c37c2e3edc1f0 100644
--- a/src/main/java/org/jastadd/tooling/RelAstGrammarSyntaxHighlighter.java
+++ b/src/main/java/org/jastadd/tooling/RelAstGrammarSyntaxHighlighter.java
@@ -62,7 +62,7 @@ public class RelAstGrammarSyntaxHighlighter extends SyntaxHighlighterBase {
 
   @NotNull
   @Override
-  public TextAttributesKey[] getTokenHighlights(IElementType tokenType) {
+  public TextAttributesKey @NotNull [] getTokenHighlights(IElementType tokenType) {
 
     if (tokenType.equals(RelAstGrammarTypes.ABSTRACT)) {
       return KEYWORD_KEYS;
diff --git a/src/main/java/org/jastadd/tooling/psi/RelAstGrammarElementFactory.java b/src/main/java/org/jastadd/tooling/psi/RelAstGrammarElementFactory.java
index 10a87a86f102f4a236019675f51c03ffa7da9480..df3bef4d1782301d2a97cbe908e2a8adc9f530e6 100644
--- a/src/main/java/org/jastadd/tooling/psi/RelAstGrammarElementFactory.java
+++ b/src/main/java/org/jastadd/tooling/psi/RelAstGrammarElementFactory.java
@@ -5,7 +5,14 @@ import com.intellij.psi.PsiFileFactory;
 import org.jastadd.tooling.RelAstGrammarFileType;
 import org.jastadd.tooling.parser.RelAstGrammarTypes;
 
+import java.util.Objects;
+
 public class RelAstGrammarElementFactory {
+
+  private RelAstGrammarElementFactory() {
+    throw new IllegalStateException("Utility class");
+  }
+
   public static RelAstGrammarDeclaredName createDeclaredName(Project project, String name) {
     final RelAstGrammarFile file = createFile(project, name + ";");
     return (RelAstGrammarDeclaredName) file.getFirstChild().getFirstChild();
@@ -13,7 +20,7 @@ public class RelAstGrammarElementFactory {
 
   public static RelAstGrammarTypeReference createTypeReference(Project project, String name) {
     final RelAstGrammarFile file = createFile(project, "X : " + name + ";");
-    return (RelAstGrammarTypeReference) (file.getFirstChild().getNode().findChildByType(RelAstGrammarTypes.TYPE_REFERENCE).getPsi());
+    return (RelAstGrammarTypeReference) (Objects.requireNonNull(file.getFirstChild().getNode().findChildByType(RelAstGrammarTypes.TYPE_REFERENCE)).getPsi());
   }
 
   public static RelAstGrammarFile createFile(Project project, String text) {
diff --git a/src/main/java/org/jastadd/tooling/psi/RelAstGrammarTypeReferenceManipulator.java b/src/main/java/org/jastadd/tooling/psi/RelAstGrammarTypeReferenceManipulator.java
index f05b01aa1bb88a3a7b15d4c9c1d2f4687587974f..38112626dddc2521650a3af32c2e7490ad20fee0 100644
--- a/src/main/java/org/jastadd/tooling/psi/RelAstGrammarTypeReferenceManipulator.java
+++ b/src/main/java/org/jastadd/tooling/psi/RelAstGrammarTypeReferenceManipulator.java
@@ -26,16 +26,4 @@ public class RelAstGrammarTypeReferenceManipulator extends AbstractElementManipu
       throw new IncorrectOperationException(e);
     }
   }
-
-//  @Nullable
-//  @Override
-//  public PsiElement handleContentChange(@NotNull PsiElement element, String newContent) throws IncorrectOperationException {
-//    if (element instanceof RelAstGrammarTypeReference) {
-//      RelAstGrammarTypeReference ref = (RelAstGrammarTypeReference) element;
-//      ref.setName(newContent);
-//    } else {
-//      throw new IncorrectOperationException("Called with wrong element type " + element.getClass().getName());
-//    }
-//    return element;
-//  }
 }
diff --git a/src/main/java/org/jastadd/tooling/psi/impl/RelAstGrammarNamedElementImpl.java b/src/main/java/org/jastadd/tooling/psi/impl/RelAstGrammarNamedElementImpl.java
index fd20d16f96cf2dad7696f9874d49f080413b2734..11c41f499e3e529a2cf16b801b251b5a3f934ac1 100644
--- a/src/main/java/org/jastadd/tooling/psi/impl/RelAstGrammarNamedElementImpl.java
+++ b/src/main/java/org/jastadd/tooling/psi/impl/RelAstGrammarNamedElementImpl.java
@@ -10,7 +10,7 @@ import org.jetbrains.annotations.Nullable;
 
 public abstract class RelAstGrammarNamedElementImpl extends ASTWrapperPsiElement implements RelAstGrammarNamedElement {
 
-  public RelAstGrammarNamedElementImpl(@NotNull ASTNode node) {
+  protected RelAstGrammarNamedElementImpl(@NotNull ASTNode node) {
     super(node);
   }
 
@@ -21,7 +21,7 @@ public abstract class RelAstGrammarNamedElementImpl extends ASTWrapperPsiElement
   }
 
   @NotNull
-  public PsiReference[] getReferences() {
+  public PsiReference @NotNull [] getReferences() {
     return ReferenceProvidersRegistry.getReferencesFromProviders(this);
   }