BufferedWriter can use threaded i/o?

Question

Dear all,
I read BufferedWriter.java from java source code, and found that it is not using thread to flushBuffer. I am wondering if we use thread to write out buffer when buffer is full, whether it will improve the write performance? -- That is, when the buffer size > nChars (the capacity of the buffer), we just use another thread to write out this buffer.
Is it possible to do so? How this can be implemented? Since I need to write out a very large file, but requires the processing time to be minimized.
   void flushBuffer() throws IOException {
          ensureOpen();
          if (nextChar == 0) return;
          out.write(cb, 0, nextChar);
          nextChar = 0;
   public void write(int c) throws IOException {
          ensureOpen();
          if (nextChar >= nChars)
               flushBuffer();
          cb[nextChar++] = (char) c;
   }Thanks!

Answer 1

No doubt it could be done, although there's obviously
no flag to tell the existing BufferedWriters to do it.
You would have to write your own version. One thread
writing full buffers, another one creating new buffers
and filling them. Could be an interesting project.
Would also be interesting to find out whether that
shortened the total time required to write the file at
all.Thanks DrClap, I think I only need to modify the flushBuffer() method in BufferedWriter code, since all other write() method will call this method when the
buffer is full. In flushBuffer(), first set nextChar = 0; then just create a thread for io output, such as:
new WriterThread(buffer); // inner class
                          // in constructor call run()
and in thread run method, do actually write:
public void run() {
   if (buffer.length == 0) return;
   ensureOpen(); // ensure the writer is open
   out.write(buffer, 0, buffer.length ); // write out buffer
}Is this ok?
Thanks!