java 获取 apk的MD5值

网上看到的几种获取方式总结一下：

最简单的一种：String MD5 = DigestUtils.md5Hex(new FileInputStream(path));

最基本的一种：

    private final static String[] strHex = { "0", "1", "2", "3", "4", "5",
              "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };
  
     public static String getMD5One(String path) {
          StringBuffer sb = new StringBuffer();
         try {
              MessageDigest md = MessageDigest.getInstance("MD5");
              byte[] b = md.digest(FileUtils.readFileToByteArray(new File(path)));
              for (int i = 0; i < b.length; i++) {
                 int d = b[i];
                if (d < 0) {
                     d += 256;
                 }
                 int d1 = d / 16;
                 int d2 = d % 16;
                 sb.append(strHex[d1] + strHex[d2]);
             }
         } catch (NoSuchAlgorithmException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
         return sb.toString();
     }

补码的形式：

public static String getMD5Two(String path) {
          StringBuffer sb = new StringBuffer("");
          try {
              MessageDigest md = MessageDigest.getInstance("MD5");
              md.update(FileUtils.readFileToByteArray(new File(path)));
              byte b[] = md.digest();
              int d;
              for (int i = 0; i < b.length; i++) {
                  d = b[i];
                 if (d < 0) {
                     d = b[i] & 0xff;
                     // 与上一行效果等同
                     // i += 256;
                 }
                 if (d < 16)
                     sb.append("0");
                 sb.append(Integer.toHexString(d));
             }
         } catch (NoSuchAlgorithmException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
         return sb.toString();
     }

这种适合大型文件

public static String getMD5Three(String path) {
          BigInteger bi = null;
          try {
              byte[] buffer = new byte[8192];
              int len = 0;
              MessageDigest md = MessageDigest.getInstance("MD5");
              File f = new File(path);
              FileInputStream fis = new FileInputStream(f);
              while ((len = fis.read(buffer)) != -1) {
                 md.update(buffer, 0, len);
             }
             fis.close();
             byte[] b = md.digest();
             bi = new BigInteger(1, b);
         } catch (NoSuchAlgorithmException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
         return bi.toString(16);
     }