I recently came across FileChannel, I am a big fan of RandomAccessFile. But I am wondering why would I pick FileChannel over RandomAccessFile for reading from a file and writing that content to another.
Is there any specific performance reason? I dont want to use locking of FileChannel for any purpose as I believe that could be one of the reasons why filechannel can be used. I don't want to use BufferReader or anything like that as suggested in other StackOverflow response.
FileChannel API says: A region of a file may be mapped directly into memory; for large files this is often much more efficient than invoking the usual read or write methods.
There is nothing to choose between them unless you use a FileChannel with direct buffers and never access the data yourself, e.g. you only copy it to a SocketChannel. This is faster because data never has to cross the JNI/JVM boundary.
But I am wondering why you don't pick BufferedReader. It will certainly be orders of magnitude faster than either of these for reading a file line by line.
RandomAccessFile is good in performance plus it allows to read and write most major types directly.
RandomAccessFile source:
See that RandomAccessFile is actually using FileChannel under the hood...
public final FileChannel getChannel() {
synchronized (this) {
if (channel == null) {
channel = FileChannelImpl.open(fd, true, rw, this);
/*
* FileDescriptor could be shared by FileInputStream or
* FileOutputStream.
* Ensure that FD is GC'ed only when all the streams/channels
* are done using it.
* Increment fd's use count. Invoking the channel's close()
* method will result in decrementing the use count set for
* the channel.
*/
fd.incrementAndGetUseCount();
}
return channel;
}
}
