在java中检查新xml文件的最佳方法

i am writing a program that parses xml files that hold tourist attractions for cities. each city has it's own xml and the nodes have info like cost, address etc... i want to have a thread on a timer to check for new xml files or more recent versions of existing ones in a specific directory. creating the thread is not the problem. i just have no idea what the best way to check for these new files or changed files is. does anyone have any suggestions as to an easy way to make do that. i was thinking of crating a csv file with names and date altered info for each file processed and then checking against this csv file when i go to check for new or altered xml, but that seems overly complicated and i would like a better solution. i have no code to offer at this point for this mechanism i am just looking for a direction to go in. the idea is as i get xml's for different cities fitting the schema that it will update my db automatically next time the program runs or periodically if already running. i am writing a program that parses xml files th