docs: public void add(final ClassLoader classLoader) {
          if (classLoader == null) {
              return;
          }
          if (added.add(classLoader)) {
              final ClassLoaderHandlerRegistryEntry entry = getRegistryEntry(classLoader);
              if (entry != null) {
                  classLoaderOrder.add(new SimpleEntry<>(classLoader, entry));
              }
          }
      }