code: private static <T> T attemptLoad(
              final Class<T> ofClass,
              final String className) {
          if (LOG.isLoggable(Level.FINEST)) {
              LOG.finest("Attempting service load: " + className);
          }
          Level level;
          Throwable thrown;
          try {
              Class<?> clazz = Class.forName(className);
              if (!ofClass.isAssignableFrom(clazz)) {
                  if (LOG.isLoggable(Level.WARNING)) {
                      LOG.warning(clazz.getName() + " is not assignable to "
                              + ofClass.getName());
                  }
                  return null;
              }
              return ofClass.cast(clazz.newInstance());
          } catch (LinkageError ex) {
              level = Level.FINEST;
              thrown = ex;
          } catch (ClassNotFoundException ex) {
              level = Level.FINEST;
              thrown = ex;
          } catch (InstantiationException ex) {
              level = Level.WARNING;
              thrown = ex;
          } catch (IllegalAccessException ex) {
              level = Level.WARNING;
              thrown = ex;
          }
          LOG.log(level,
                  "Could not load " + ofClass.getSimpleName()
                  + " instance: " + className,
                  thrown);
          return null;
      }
docs: Attempts to load the specified implementation class.
  Attempts will fail if - for example - the implementation depends
  on a class not found on the classpath.
  
  @param className implementation class to attempt to load
  @return service instance, or {@code null} if the instance could not be
  loaded