java 获取string哈希值 java获取文件的哈希值

public static byte[] createChecksum(String filename) throws Exception {   

   InputStream fis =  new FileInputStream(filename);          //<span style="color: rgb(51, 51, 51); font-family: arial; font-size: 13px; line-height: 20px;">将流类型字符串转换为String类型字符串</span>   

   

   byte[] buffer = new byte[1024];   

   MessageDigest complete = MessageDigest.getInstance("MD5"); //如果想使用SHA-1或SHA-256，则传入SHA-1,SHA-256   

   int numRead;   

   

   do {   

       numRead = fis.read(buffer);    //从文件读到buffer，最多装满buffer   

       if (numRead > 0) {   

       complete.update(buffer, 0, numRead);  //用读到的字节进行MD5的计算，第二个参数是偏移量   

       }   

   } while (numRead != -1);   

   

   fis.close();   

   return complete.digest();   

}   

   

public static String getMD5Checksum(String filename) throws Exception {   

   byte[] b = createChecksum(filename);   

   String result = "";   

   

   for (int i=0; i < b.length; i++) {   

       result += Integer.toString( ( b[i] & 0xff ) + 0x100, 16).substring(1);//加0x100是因为有的b[i]的十六进制只有1位   

   }   

   return result;   

}