public Logger(String filename) throws FileNotFoundException, IOException {
// ps = new PrintStream(new FileOutputStream(new File(filename)));
File f = new File(filename);
fos = new FileOutputStream(f);
ps = new PrintStream(fos);
ps.println("Logging started");
ps.flush();
sw = new Stopwatch();
sw.reset();
}
public void log(String s) {
ps.println(sw.elapsed() + ": " + s);
ps.flush();
}