Why use Java's AsynchronousFileChannel?

It's a channel that you can use to read files asynchronously, i.e. the I/O operations are done on a separate thread, so that the thread you're calling it from can do other things while the I/O operations are happening.

For example: The read() methods of the class return a Future object to get the result of reading data from the file. So, what you can do is call read(), which will return immediately with a Future object. In the background, another thread will read the actual data from the file. Your own thread can continue doing things, and when it needs the read data, you call get() on the Future object. That will then return the data (if the background thread hasn't completed reading the data, it will make your thread block until the data is ready). The advantage of this is that your thread doesn't have to wait the whole length of the read operation; it can do some other things until it really needs the data.

See the documentation.

Note that AsynchronousFileChannel will be a new class in Java SE 7, which is not released yet.

Thanks, but I was wondering more about the efficiency reasons -- I can't see why performing the I/O in another thread helps. One thread always has to block for the I/O, and there is no reported resource re-use, hardware feature utilization, or any other performance-enhancing behaviors.

Joey Bell 2010-05-04 18:18:12

The advantage of this is that you *don't* need two threads. If you are writing a large blob of data, at the low-level, the disk controller does the job of writing data to disk before signalling an interrupt which goes up the stack to invoke your completion handler.Your thread needn't block during this process and can do other stuff. You use one less thread, the thread scheduler manages one less thread, you don't need to use java notify. Basically, you utilize less resources to do the same thing.

lenkite 2010-07-09 11:01:54

ansaurus

tags:

views:

answers:

Why use Java's AsynchronousFileChannel?

related questions