code: public static String convertFile32(File file)
      {
          if(file==null || !file.exists())
          {
              return null;
          }
          InputStream fis = null;
          try {
              fis = new FileInputStream(file);
              byte[] buffer = new byte[1024];
              MessageDigest md5 = MessageDigest.getInstance("MD5");
              int numRead = 0;
              while ((numRead = fis.read(buffer)) > 0)
              {
                  md5.update(buffer, 0, numRead);
              }
              byte[] b=md5.digest();
              StringBuilder sb = new StringBuilder(b.length * 2);
              for (int i = 0; i < b.length; i++) {
                  sb.append(hexChars[(b[i] & 0xf0) >>> 4]);
                  sb.append(hexChars[b[i] & 0x0f]);
              }
              return sb.toString();
          }
          catch (Exception e)
          {
              e.printStackTrace();
          }
          finally
          {
              if(fis!=null)
              {
                  try
                  {
                      fis.close();
                  }
                  catch (IOException e)
                  {
                      e.printStackTrace();
                  }
              }
          }
          return null;
      }
docs: 获取文件的MD5值 32位
  @param file 文件
  @return 32位MD5值