class FilterChain {

  private Filter chain;


  /**
   * Adds filter.
   */
  public void addFilter(Filter filter) {<FILL_FUNCTION_BODY>}

  /**
   * Execute filter chain.
   */
  public String execute(Order order) {
    if (chain != null) {
      return chain.execute(order);
    } else {
      return "RUNNING...";
    }
  }
}

    if (chain == null) {
      chain = filter;
    } else {
      chain.getLast().setNext(filter);
    }
  
<no_super_class>