code: public static LoadBalanceStrategy build(NaviSelectorStrategy selectorStg,
              NaviFailStrategy failStg) {
          if (NaviSelectorStrategy.RANDOM.equals(selectorStg)) {
              return new RandomLoadBalanceStrategy(howToDealFailure(failStg));
          } else if (NaviSelectorStrategy.ROUNDROBIN.equals(selectorStg)) {
              return new RRLoadBalanceStrategy(howToDealFailure(failStg));
          } else if (NaviSelectorStrategy.NATURALORDER.equals(selectorStg)) {
              return new NatureOrderLoadBalanceStrategy(howToDealFailure(failStg));
          }
          return new RandomLoadBalanceStrategy(howToDealFailure(failStg));
      }
docs: 构造负载均衡封装
  
  @param selectorStg
  @param failStg
  @return