code: public final static boolean isValidURL(String url) {
          if (url == null) {
              return false;
          } else {
              return Patterns.WEB_URL.matcher(url).matches();
          }
      }
docs: Uses androids android.util.Patterns.WEB_URL to check if an url is valid.
  
  @param url Address to check
  @return true if the <code>url</code> is a valid web address.