}
        }
        if (!found) {
            requestProperties.put(key, values);
        }
        connection.setRequestProperty(key, value);
    }

    @Override
    public void addRequestProperty(final String key, final String value) {
        if (key == null) {
            throw new NullPointerException();
        }
        List values = null;

        }
        if (!found) {
            this.requestProperties.put(key, values);
        }
        this.connection.setRequestProperty(key, value);
    }

    @Override
    public void addRequestProperty(final String key, final String value) {
        if (key == null) {
            throw new NullPointerException();
        }
        List<String> values = null;