getProperties().storeToXML(os, comment);
    }

    @Override
    public Set<String> stringPropertyNames() {
        return getProperties().stringPropertyNames();
    }

    @Override
    public String toString() {
        return getProperties().toString();
    }

    @Override
    public Collection<Object> values() {

        // ----------------------------------------------------------------------
        Set<String> sys = SystemProperties.getSystemProperties().stringPropertyNames();
        userProperties.stringPropertyNames().stream()
                .filter(k -> !sys.contains(k))
                .forEach(k -> System.setProperty(k, userProperties.getProperty(k)));
    }

    @Nonnull
    public static Map<String, String> toMap(Properties properties) {
        requireNonNull(properties, "properties");
        HashMap<String, String> map = new HashMap<>();
        for (String key : properties.stringPropertyNames()) {
            map.put(key, properties.getProperty(key));
        }
        return map;
    }

    @Nonnull
    public static Properties toProperties(Map<String, String> properties) {