[util] - byte to hex string

   private static final char[] hexDigits = {
        '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'
    };

   public static String toString(byte[] ba, int offset, int length) {
        char[] buf = new char[length * 2];
        int j = 0;
        int k;

        for (int i = offset; i < offset + length; i++) {
            k = ba[i];
            buf[j++] = hexDigits[(k >>> 4) & 0x0F];
            buf[j++] = hexDigits[ k        & 0x0F];
        }
        return new String(buf);
    }

    public static String toString(byte[] ba) {
        return toString(ba, 0, ba.length);
    }

바이트 배열을 헥사 문자열로 변환하는 유틸