一、通道（Channel）: 用于源节点与目标节点的连接。在java NIO中负责缓冲区中数据的传输。Channel本身不存储数据，因此需要配合缓冲区进行传输。

二、通道的主要实现类

java.nio.channels.Channel接口： |– FileChannel |– SocketChannel |– ServerSocketChannel |– DatagramChannel

三、获取通道

1、java针对支持通道的类提供了getChannel()方法 本地IO： FileInputStream/FileOutputStream RandomAccessFile 网络IO： Socket ServerSocket DatagramSocket 2、在jdk1.7中NIO.2针对各个通道提供了静态方法open() 3、在jdk1.7中NIO.2的Files工具类的newByteChannel()

@Test  //利用通道完成文件复制    public void test4() throws FileNotFoundException{        FileInputStream fis = new FileInputStream("1.mp4");        FileOutputStream fos=new FileOutputStream("2.mp4");        //1、获取通道        FileChannel inChannel = fis.getChannel();        FileChannel outChannel = fos.getChannel();        try {            //2、分配一个指定大小的缓冲区            ByteBuffer buf=ByteBuffer.allocate(1024);            //3、将通道中的数据存入缓冲区            while(inChannel.read(buf)!=-1){                //4、将缓冲区中的数据写入通道中                buf.flip();  //切换读取数据模式                outChannel.write(buf);                buf.clear();            }        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }finally{            try {                outChannel.close();            } catch (Exception e) {                e.printStackTrace();            }            try {                inChannel.close();            } catch (IOException e) {                e.printStackTrace();            }            try {                fos.close();            } catch (IOException e) {                e.printStackTrace();            }            try {                fis.close();            } catch (IOException e) {                e.printStackTrace();            }           }    }    @Test  //使用直接缓冲区完成文件的复制    public void test5() throws IOException{        FileChannel inChannel=FileChannel.open(Paths.get("1.mp4"),StandardOpenOption.READ);        FileChannel outChannel=FileChannel.open(Paths.get("2.mp4"),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE_NEW);        //内存映射文件        MappedByteBuffer inMappedBuf=inChannel.map(MapMode.READ_ONLY,0,inChannel.size());        MappedByteBuffer outMappedBuf=outChannel.map(MapMode.READ_WRITE,0,inChannel.size());        //直接对缓冲区进行数据的读写操作        byte[] dst=new byte[inMappedBuf.limit()];        inMappedBuf.get(dst);        outMappedBuf.put(dst);        outChannel.close();        inChannel.close();    }

四、通道之间的数据传输

@Test  // 通道之间的数据传输(直接缓冲区)    public void test6() throws IOException{        FileChannel inChannel=FileChannel.open(Paths.get("1.mp4"),StandardOpenOption.READ);        FileChannel outChannel=FileChannel.open(Paths.get("2.mp4"),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE);        //inChannel.transferTo(0,inChannel.size(),outChannel);   //二选一即可        outChannel.transferFrom(inChannel,0,inChannel.size());        outChannel.close();        inChannel.close();    }