Java Programming

Hey everyone,

I'm trying to monitor changes within a directory. What I am doing is iterating through all of the directories and populating an array list with the files and directories within a root folder. For some reason my program notifies me when a change was made to a small number of files however when I test it on my hard drive with over a hundred gigs of stuff it doesn't work. My guess is that there might be a size limit on the array list holding the files within the root.

Just to give you a better picture of what I'm doing:
I have an array list to hold the contents of the root. This is being populated correctly.
I have a variable to hold the last modified date.
I iterate through the array list and check each modified date and see if it is greater than the one in memory. While it works on a small folder, it does not work on one that contains a lot of files.

Any suggestions? Any help would be much appreciated.