flush in java.io.FileWriter

Question

I have a question in my mind that, while writing into the file, before closing is done, should we include flush()??. If so what it will do exactly? dont streams auto flush??

Answer 1

Another usecase for flushing in program is writing progress of longrunning job into file (so it can be stopped and restarted later. You want to be sure that data is safe on the drive.

while (true) {
  computeStuff();
  progresss += 1;
  out.write(String.format("%d", progress));
  out.flush();
}
out.close();