System, which has a large number of map [key] way, often appear the key does not exist in the map, an error, which is not easy to locate the key problems, tracking more vexed, the hope is that the LOG output, see ran out of the subscript there is no exception in the couldn't find the key value,
Don't want to change the code to determine whether the KEY first, then operate the way, that can greatly increase the amount of code,