code: String getQueryString(Map<String, String> params) {
  		StringBuilder builder = new StringBuilder();
  		try {
  			boolean first = true;
  			for (Map.Entry<String,String> entry : params.entrySet()) {
  				if (first) {
  					first = false;
  				} else {
  					builder.append("&");
  				}
  				builder.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
  				builder.append("=");
  				builder.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
  			}
  		} catch (UnsupportedEncodingException e) {
  			throw new RuntimeException(
  					"Your Java version does not support UTF-8 encoding.");
  		}
  
  		return builder.toString();
  	}
docs: Returns the query string of a URL from a parameter list.
  
  @param params
  Map with parameters
  @return query string