Sha256 encryption tool class

public class SHA256Util {

    /**
     *  use java Native summary implementation SHA256 encryption 
     *
     * @param str  Message before encryption 
     * @return
     */
    public static String getSHA256String(String str) {
        String encodeStr = "";
        try {
            MessageDigest messageDigest = MessageDigest.getInstance("SHA-256");
            messageDigest.update(str.getBytes("UTF-8"));
            encodeStr = byte2Hex(messageDigest.digest());
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return encodeStr;
    }

    /**
     * byte[] To 16 Base number 
     *
     * @param bytes
     * @return
     */
    private static String byte2Hex(byte[] bytes) {
        StringBuffer stringBuffer = new StringBuffer();
        for (int i = 0; i < bytes.length; i++) {
            String temp = Integer.toHexString(bytes[i] & 0xFF);
            if (temp.length() == 1) {
                stringBuffer.append("0");
            }
            stringBuffer.append(temp);
        }
        return stringBuffer.toString();
    }
}