code: public static Marker getMarker(final String name) {
          Marker result = MARKERS.get(name);
          if (result == null) {
              MARKERS.putIfAbsent(name, new Log4jMarker(name));
              result = MARKERS.get(name);
          }
          return result;
      }
docs: Retrieves a Marker or create a Marker that has no parent.
  
  @param name The name of the Marker.
  @return The Marker with the specified name.
  @throws IllegalArgumentException if the argument is {@code null}