Java function returns empty string

I'm trying to parse data from my server in Java with jsoup. I wrote a new function and it should return data in string format, but it returns blank string. Here is my code:

public String doc;

public String pare(final String url){
        Thread downloadThread = new Thread() {
            public void run() {
                try {
                    doc = Jsoup.connect(url).get().toString();
                }
                catch (IOException e) {
                    e.printStackTrace();
                }
            }
        };
        downloadThread.start();
        return  doc;
}