code: public void registerStaticFields(final Class<?>... classes) {
          for (final Class<?> c : classes) {
              final List<Field> fields = allFields(c);
              for (final Field field : fields) {
                  final int mods = field.getModifiers();
                  if (Modifier.isStatic(mods) && !field.getType().isPrimitive()) {
                      // System.out.println(c + " . " + field.getName());
                      registerConstant(c, field.getName());
                  }
              }
          }
      }
docs: registers all static fields of these classes. Those static fields won't be cloned when an instance of the class is cloned.
  This is useful i.e. when a static field object is added into maps or sets. At that point, there is no way for the cloner to know that it was
  static except if it is registered.
  
  @param classes
  array of classes