java获取一份文件的MD5值

  publicstatic String getMd5ByFile(File file) {

    String md5Value = null;
    try{
        FileInputStream in =new FileInputStream(file);
        MappedByteBuffer byteBuffer = in.getChannel().map(FileChannel.MapMode.READ_ONLY,0, file.length());
        MessageDigest md5 = MessageDigest.getInstance("MD5");
        md5.update(byteBuffer);
        BigInteger bi =new BigInteger(1, md5.digest());
        md5Value= bi.toString(16);
    }catch (Exception e) {
        e.printStackTrace();
    }finally {
            if(null!= in) {
                try{
                in.close();
            }catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    returnmd5Value ;
    }