title: get file modification time
body: <p>i want to write a code for monitoring file changes and reacting to changes.
  so i write a TimerTask to periodically check the modification of file
  but i have a problem:
  when file is open by other programs such as excel or word and i'm closing the file
  without any changes,value  File.lastModified() is changing.
  i am also trying to get modification date by running dir shell script, it's work fine but
  it only has minute accuracy!
  can any one help me?
  thanks</p>