可参考:

1     /** 2      * 计算文件的MD5码 3      * @param file 4      * @return 5      */ 6     public static String getMD5(File file) { 7         FileInputStream fis = null; 8         try { 9             MessageDigest md = MessageDigest.getInstance("MD5");10             fis = new FileInputStream(file);11             byte[] buffer = new byte[8192];12             int length = -1;13             System.out.println("开始算");14             while ((length = fis.read(buffer)) != -1) {15                 md.update(buffer, 0, length);16             }17             System.out.println("算完了");18             return bytesToString(md.digest());19         } catch (IOException ex) {20             Logger.getLogger(MD5Util.class.getName()).log(Level.SEVERE, null, ex);21             return null;22         } catch (NoSuchAlgorithmException ex) {23             Logger.getLogger(MD5Util.class.getName()).log(Level.SEVERE, null, ex);24             return null;25         } finally {26             try {27                 fis.close();28             } catch (IOException ex) {29                 Logger.getLogger(MD5Util.class.getName()).log(Level.SEVERE, null, ex);30             }31         }32     }33 34     /**35      * 得到文件的SHA码,用于校验36      * @param file37      * @return38      */39     public static String getSHA(File file) {40         FileInputStream fis = null;41         try {42             MessageDigest md = MessageDigest.getInstance("SHA");43             fis = new FileInputStream(file);44             byte[] buffer = new byte[8192];45             int length = -1;46             System.out.println("开始算");47             while ((length = fis.read(buffer)) != -1) {48                 md.update(buffer, 0, length);49             }50             System.out.println("算完了");51             return bytesToString(md.digest());52         } catch (IOException ex) {53             Logger.getLogger(MD5Util.class.getName()).log(Level.SEVERE, null, ex);54             return null;55         } catch (NoSuchAlgorithmException ex) {56             Logger.getLogger(MD5Util.class.getName()).log(Level.SEVERE, null, ex);57             return null;58         } finally {59             try {60                 fis.close();61             } catch (IOException ex) {62                 Logger.getLogger(MD5Util.class.getName()).log(Level.SEVERE, null, ex);63             }64         }65     }66