[UtilityClass] [issue #2384] Added a test to confirm no issue.

added some tests to confirm that lombok makes things static if needed.

src/core/lombok/eclipse/handlers/HandleUtilityClass.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2015 The Project Lombok Authors.
+ * Copyright (C) 2015-2020 The Project Lombok Authors.
  * 
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -113,7 +113,7 @@ public class HandleUtilityClass extends EclipseAnnotationHandler<UtilityClass> {
 		if (typeNode.up().getKind() == Kind.COMPILATION_UNIT) markStatic = false;
 		if (markStatic && typeNode.up().getKind() == Kind.TYPE) {
 			TypeDeclaration typeDecl = (TypeDeclaration) typeNode.up().get();
-			if ((typeDecl.modifiers & ClassFileConstants.AccInterface) != 0) markStatic = false;
+			if ((typeDecl.modifiers & (ClassFileConstants.AccInterface | ClassFileConstants.AccAnnotation | ClassFileConstants.AccEnum)) != 0) markStatic = false;
 		}
 		
 		if (markStatic) classDecl.modifiers |= ClassFileConstants.AccStatic;

src/core/lombok/javac/handlers/HandleUtilityClass.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2015 The Project Lombok Authors.
+ * Copyright (C) 2015-2020 The Project Lombok Authors.
  * 
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -110,7 +110,7 @@ public class HandleUtilityClass extends JavacAnnotationHandler<UtilityClass> {
 		if (typeNode.up().getKind() == Kind.COMPILATION_UNIT) markStatic = false;
 		if (markStatic && typeNode.up().getKind() == Kind.TYPE) {
 			JCClassDecl typeDecl = (JCClassDecl) typeNode.up().get();
-			if ((typeDecl.mods.flags & Flags.INTERFACE) != 0) markStatic = false;
+			if ((typeDecl.mods.flags & (Flags.INTERFACE | Flags.ANNOTATION | Flags.ENUM)) != 0) markStatic = false;
 		}
 		
 		if (markStatic) classDecl.mods.flags |= Flags.STATIC;

test/transform/resource/after-delombok/UtilityClassInner.java

@@ -0,0 +1,8 @@
+class UtilityClassInner {
+	static final class UtilClass {
+		@java.lang.SuppressWarnings("all")
+		private UtilClass() {
+			throw new java.lang.UnsupportedOperationException("This is a utility class and cannot be instantiated");
+		}
+	}
+}

test/transform/resource/after-ecj/UtilityClassInner.java

@@ -0,0 +1,11 @@
+class UtilityClassInner {
+  static final @lombok.experimental.UtilityClass class UtilClass {
+    private @java.lang.SuppressWarnings("all") UtilClass() {
+      super();
+      throw new java.lang.UnsupportedOperationException("This is a utility class and cannot be instantiated");
+    }
+  }
+  UtilityClassInner() {
+    super();
+  }
+}

test/transform/resource/before/UtilityClassInner.java

@@ -0,0 +1,4 @@
+class UtilityClassInner {
+	@lombok.experimental.UtilityClass
+	class UtilClass {}
+}