1. 利用通道完成檔案的複製(非直接緩衝區)

    @Test
    public void test1(){

        FileInputStream fis = null;
        FileOutputStream fos = null;
        FileChannel inChannel = null;
        FileChannel outChannel = null;
        try {
            fis = new FileInputStream("1.jpg");
            fos = new FileOutputStream("2.jpg");

            
 
//獲取通道
            inChannel = fis.getChannel();
            outChannel = fos.getChannel();

            //分配製定大小的緩衝區
            ByteBuffer buf = ByteBuffer.allocate(1024);

            //將通道中的資料存入緩衝區中
            while (inChannel.read(buf) != -1){
                //切換為讀取資料的模式
                buf.flip();
                
 
//將緩衝區中的資料寫入通道
                outChannel.write(buf);
                buf.clear();
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (outChannel != null){
                try {
                    outChannel.close();
                } catch
 
 (IOException e) {
                    e.printStackTrace();
                }
            }
            if (inChannel != null){
                try {
                    inChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (fos != null){
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (fis != null){
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    }

2. 使用直接緩衝區完成檔案的複製(記憶體對映檔案)

@Test
    public void test2() throws IOException{
        FileChannel inChannel = FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);
        FileChannel outChannel = FileChannel.open(Paths.get("3.jpg"), StandardOpenOption.READ,StandardOpenOption.WRITE,StandardOpenOption.CREATE_NEW);

        //記憶體對映檔案
        MappedByteBuffer inMappedBuf = inChannel.map(FileChannel.MapMode.READ_ONLY, 0, inChannel.size());
        MappedByteBuffer outMappedBuf = outChannel.map(FileChannel.MapMode.READ_WRITE, 0, inChannel.size());

        //直接對緩衝區進行資料的讀寫操作
        byte[] dst = new byte[inMappedBuf.limit()];
        inMappedBuf.get(dst);
        outMappedBuf.put(dst);

        inChannel.close();
        outChannel.close();
    }

第二種方式速度更快，因為通過管道獲取的緩衝區直接對應著實體記憶體，不再建立流物件和新的緩衝區。