private static long getLatestModifiedDate(File dir) {
File[] files = dir.listFiles();
long latestDate = 0;
for (File file : files) {
long fileModifiedDate = file.isDirectory()
? getLatestModifiedDate(file) : file.lastModified();
if (fileModifiedDate > latestDate) {
latestDate = fileModifiedDate;
}
}
return Math.max(latestDate, dir.lastModified());
}