sha1加密java代码详解编程语言

 public static String getSha1(String str){ 
        if(str==null||str.length()==0){ 
            return null; 
        } 
        char hexDigits[] = {'0','1','2','3','4','5','6','7','8','9', 
                'a','b','c','d','e','f'}; 
        try { 
            MessageDigest mdTemp = MessageDigest.getInstance("SHA1"); 
            mdTemp.update(str.getBytes("UTF-8")); 
 
            byte[] md = mdTemp.digest(); 
            int j = md.length; 
            char buf[] = new char[j*2]; 
            int k = 0; 
            for (int i = 0; i < j; i++) { 
                byte byte0 = md[i]; 
                buf[k++] = hexDigits[byte0 >>> 4 & 0xf]; 
                buf[k++] = hexDigits[byte0 & 0xf];       
            } 
            return new String(buf); 
        } catch (Exception e) { 
            // TODO: handle exception 
            return null; 
        } 
    }