PrintWriter print vs println

Question

I got a server waiting for messages and a client sending him messages, when using

    PrintWriter out = new PrintWriter(lpSocket.getOutputStream(), true);
    String msg;
    BufferedReader userIn = new BufferedReader(new InputStreamReader(System.in));
    while ((msg = userIn.readLine()) != null)
        out.print(msg + (char) 10);

nothing happens, meaning the server just keep waiting for a message that never arrive. When I change the out.print to out.println it works.

I would like to know why

Answer 1

By default, PrintWriter calls flush in println , whereas it doesn't do this in print . You can fix this by adding out.flush() after your out.print call