code: private static String buildUrlWithQueryString(String url, Map<String, String> queryParas) {
  		if (queryParas == null || queryParas.isEmpty())
  			return url;
  		
  		StringBuilder sb = new StringBuilder(url);
  		boolean isFirst;
  		if (!url.contains("?")) {
  			isFirst = true;
  			sb.append("?");
  		}
  		else {
  			isFirst = false;
  		}
  		
  		for (Entry<String, String> entry : queryParas.entrySet()) {
  			if (isFirst) isFirst = false;	
  			else sb.append("&");
  			
  			String key = entry.getKey();
  			String value = entry.getValue();
  			if (StrKit.notBlank(value))
  				try {value = URLEncoder.encode(value, CHARSET);} catch (UnsupportedEncodingException e) {throw new RuntimeException(e);}
  			sb.append(key).append("=").append(value);
  		}
  		return sb.toString();
  	}
docs: Build queryString of the url