code: public static String getString(String key, String valueIfNull) {
          String value = System.getProperty(key);
          if (Strings.isNullOrEmpty(value)) {
              return valueIfNull;
          }
          return value;
      }
docs: Gets a system property string, or a replacement value if the property is
  null or blank.
  
  @param key
  @param valueIfNull
  @return