java计算文件32位md5值

protected static String getFileMD5(String fileName)
    {
        File file = new File(fileName);
        if(!file.exists() || !file.isFile()){
            return "";
        }
        
        byte[] buffer = new byte[2048];
        try {
            MessageDigest digest = MessageDigest.getInstance("MD5");
            FileInputStream in = new FileInputStream(file);
            while(true){
                int len = in.read(buffer,0,2048);
                if(len != -1){
                    digest.update(buffer, 0, len);
                }else{
                    break;
                }
            }
            in.close();
            
            byte[] md5Bytes  = digest.digest();
            StringBuffer hexValue = new StringBuffer();
            for (int i = 0; i < md5Bytes.length; i++) {
                int val = ((int) md5Bytes[i]) & 0xff;
                if (val < 16) {
                    hexValue.append("0");
                }
                hexValue.append(Integer.toHexString(val));
            }
            return hexValue.toString();
            
            //String hash = new BigInteger(1,digest.digest()).toString(16);
            //return hash;
            
        } catch (NoSuchAlgorithmException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return "";
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return "";
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return "";
        }
    }

how to use:

String file = "d://one.zip";
String md5 = getFileMD5(file);