code: private Method getMethod() {
          if (rules_methods.get(getClass()) == null) {
              loadMethods();
          }
          Method nextMethod = rules_methods.get(getClass()).get(next);
          if (nextMethod == null) {
              throw new RuntimeException("规则" + getClass().getName() + "中找不到规则步骤:" + next);
          }
          return nextMethod;
      }
docs: 懒加载