@Test

     public void testChannel() throws IOException {

         FileInputStream fileInputStream = new FileInputStream("Java NIO.pdf");

         FileOutputStream fileOutputStream = new FileOutputStream("2.pdf");

         // 1、获取通道

         FileChannel inChannel = fileInputStream.getChannel();

         FileChannel outChannel = fileOutputStream.getChannel();

         // 2.分配指定大小的缓冲区

         ByteBuffer byteBuffer = ByteBuffer.allocate(1024);

         // 3、将通道的数据读入缓冲区

         while (inChannel.read(byteBuffer) != -1) {

             byteBuffer.flip();// 切换缓冲区为读模式

             // 4、把缓冲区的数据写入通道

             outChannel.write(byteBuffer);

             byteBuffer.clear();// 因为需要循环多次读，需要清空缓冲区。

         }

         byteBuffer.clear();

         inChannel.close();

         outChannel.close();

         fileInputStream.close();

         fileOutputStream.close();

     }

     /**

      * 内存映射文件

      *

      * @throws IOException

      */

     @Test

     public void testMemoryMappingFile() throws IOException {

         long start = System.currentTimeMillis();

         FileChannel inChannel = FileChannel.open(Paths.get("D:\\nio.zip"), StandardOpenOption.READ);

         // 注意：StandardOpenOption.CREATE

         // 如果文件已经存在，直接覆盖，StandardOpenOption.CREATE_NEW,如果文件已经存在，就抛出异常。

         FileChannel outChannel = FileChannel.open(Paths.get("E:\\nio.zip"), StandardOpenOption.READ,

                 StandardOpenOption.WRITE, StandardOpenOption.CREATE);

         // 获取内存映射文件

         MappedByteBuffer inMappedByteBuffer = inChannel.map(MapMode.READ_ONLY, 0, inChannel.size());

         MappedByteBuffer outMappedByteBuffer = outChannel.map(MapMode.READ_WRITE, 0, inChannel.size());

         // 直接对数据进行读写

         byte[] bytes = new byte[inMappedByteBuffer.limit()];
           // 此时，如果数据读超出了一定返回会抛出异常。如果内存不足时，会抛出java.lang.OutOfMemoryError: Java heap space

         inMappedByteBuffer.get(bytes);

         outMappedByteBuffer.put(bytes);

         inChannel.close();

         outChannel.close();

         long end = System.currentTimeMillis();

         System.out.println((end - start));

     }

     public void testTransfer() throws IOException {

         FileChannel inChannel = FileChannel.open(Paths.get("D:\\nio.zip"), StandardOpenOption.READ);

         // 注意：StandardOpenOption.CREATE

         // 如果文件已经存在，直接覆盖，StandardOpenOption.CREATE_NEW,如果文件已经存在，就抛出异常。

         FileChannel outChannel = FileChannel.open(Paths.get("E:\\nio.zip"), StandardOpenOption.READ,

                 StandardOpenOption.WRITE, StandardOpenOption.CREATE);

         //inChannel.transferTo(0, inChannel.size(), outChannel);

         outChannel.transferFrom(inChannel, 0, inChannel.size());

     }