Getting and Setting modification time of file or a directory.

File file = new File("filename");

// Get the last modified time
long modifiedTime = file.lastModified();
// 0L is returned if the file does not exist

// Set the last modified time
long newModifiedTime = System.currentTimeMillis();
boolean success = file.setLastModified(newModifiedTime);
if (!success) {
// operation failed.
}