EDIT

import java.util.EnumSet;

    /**

     * EnumSets being part of the model should be immutable to make hibernate know if they have been changed.

     * Therefore any change to the enum set should result in a new enum set.

     */

    protected <T extends Enum<T>> EnumSet<T> newEnumSet(@NotNull EnumSet<T> enumSet, T additionalClass, T classToRemove) {

        EnumSet<T> result = EnumSet.copyOf(enumSet);

        if (additionalClass != null){

            result.add(additionalClass);

        }

        if (classToRemove != null){

            result.remove(classToRemove);

        }

        return result;

    }