1.星期幾取得：
LocalDate date = LocalDate.now();
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("E");
String text = date.format(formatter);
System.out.println("測試..." + text);
2.JDK API得注釋：
All letters 'A' to 'Z' and 'a' to 'z' are reserved as pattern letters. The following pattern letters are defined:
