* In a package hierarchy, the {@linkplain #descriptors} map has either zero or one entry.
     * In a module hierarchy, the descriptors map may have an arbitrary number of entries,
     * including one (so the map size cannot be used as a criterion).
     *
     * @see #isModuleHierarchy()
     */
    private final boolean isModuleHierarchy;

    /**

     * In a package hierarchy, the {@linkplain #descriptors} map has either zero or one entry.
     * In a module hierarchy, the descriptors map may have an arbitrary number of entries,
     * including one (so the map size cannot be used as a criterion).
     *
     * @see #isModuleHierarchy()
     */
    private final boolean isModuleHierarchy;

    /**