class DefaultHttpHeaders extends HttpHeaders {

    @Override
    public HttpHeaders add(HttpHeaders headers) {
        if (headers instanceof DefaultHttpHeaders) {
            this.headers.add(((DefaultHttpHeaders) headers).headers);
            return this;
        } else {
            return super.add(headers);
        }
    }

    public  DefaultHttpHeaders();
    public  DefaultHttpHeaders(boolean validate);
    protected  DefaultHttpHeaders(boolean validate, NameValidator<CharSequence> nameValidator);
    protected  DefaultHttpHeaders(DefaultHeaders<CharSequence, CharSequence, ?> headers);

}