I/O Operation On Channels Using ByteBuffer - Performance Comparision
FileChannel inChannel = new FileInputStream("input.txt").getChannel();
FileChannel outChannel = new FileOutputStream("output.txt").getChannel();
ByteBuffer buf = ByteBuffer.allocate(1024 * 1024);

while (inChannel.read(buf) != -1) {
    buf.flip();
    while (buf.hasRemaining()) {
        outChannel.write(buf);
    }
    buf.clear();
}

while (inChannel.read(buf) != -1 || buf.position() > 0) {
    buf.flip();
    outChannel.write(buf);
    buf.compact();
}

while (inChannel.read(buf) != -1) {
    buf.flip();
    outChannel.write(buf);
    buf.compact();
}
// final flush of pending output
while (buf.hasRemaining())
    outChannel.write(buf);