/**     * channel Gather/Scatter     */    public static void channelGatherScatter(){        ByteBuffer head = ByteBuffer.allocate(4);        ByteBuffer body = ByteBuffer.allocate(100);        RandomAccessFile afile = null;        RandomAccessFile bfile = null;        ReadWriteLock readWriteLock = new ReentrantReadWriteLock();        try {            afile = new RandomAccessFile("hello.txt", "r");            bfile = new RandomAccessFile("hehe.txt", "rw");            readWriteLock.readLock().lock();            FileChannel fileChannel = afile.getChannel();            ByteBuffer[] buffers = {head, body};            while (fileChannel.read(buffers) != -1){            }            head.flip();            body.flip();            System.out.println(new String(head.array()));            System.out.println(new String(body.array()));            readWriteLock.readLock().unlock();            fileChannel.close();            afile.close();            readWriteLock.writeLock().lock();            FileChannel bfileChannel = bfile.getChannel();            while (bfileChannel.write(buffers) > 0){            }            readWriteLock.writeLock().unlock();            bfileChannel.close();            bfile.close();        }catch (Exception e){            e.printStackTrace();        }    }