code: public ClassInfoList getAnnotationsOnClass(final String className) {
          if (closed.get()) {
              throw new IllegalArgumentException("Cannot use a ScanResult after it has been closed");
          }
          if (!scanSpec.enableClassInfo || !scanSpec.enableAnnotationInfo) {
              throw new IllegalArgumentException(
                      "Please call ClassGraph#enableClassInfo() and #enableAnnotationInfo() before #scan()");
          }
          final ClassInfo classInfo = classNameToClassInfo.get(className);
          return classInfo == null ? ClassInfoList.EMPTY_LIST : classInfo.getAnnotations();
      }
docs: Get annotations on the named class. This only returns the annotating classes; to read annotation parameters,
  call {@link #getClassInfo(String)} to get the {@link ClassInfo} object for the named class, then if the
  {@link ClassInfo} object is non-null, call {@link ClassInfo#getAnnotationInfo()} to get detailed annotation
  info.
  
  @param className
  The name of the class.
  @return A list of all annotation classes that were found with the named class annotation during the scan, or
  the empty list if none.