code: private static Double max(Map<String, Double> map)
      {
          Double theMax = 0.0;
          for (Double v : map.values())
          {
              theMax = Math.max(theMax, v);
          }
  
          return theMax;
      }
docs: 从map的值中找出最大值，这个值是从0开始的
  @param map
  @return