Java Sha1 加密算法

public static String getSha1(String str){    if (null == str || 0 == str.length()){        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 (NoSuchAlgorithmException e) {        e.printStackTrace();    } catch (UnsupportedEncodingException e) {        e.printStackTrace();    }}