java - 来自 Calendar.getDisplayName() 的错误工作日

Question

我正在尝试获取给定日期(例如生日)的工作日。因此，我正在使用 Calendar 对象并调用 getDisplayName() 方法。但是每次该方法返回错误值时，工作日都会提前两天。例如:输入:23.11.2015 -> Wednesday

代码:

Scanner s = new Scanner(System.in);
System.out.println("Please enter your birthday. Format: DD.MM.YYYY");
String bday = s.nextLine();
String day_of_birth = bday.substring(0, bday.indexOf(".")); // start to first dot = day
String month_of_birth = bday.substring(bday.indexOf(".")+1, bday.lastIndexOf(".")); // between first dot and last dot = month
String year_of_birth = bday.substring(bday.lastIndexOf(".")+1); // last dot to end = year
Calendar birthday = Calendar.getInstance();
birthday.set(Integer.parseInt(year_of_birth), Integer.parseInt(month_of_birth), Integer.parseInt(day_of_birth));
String weekday = birthday.getDisplayName(Calendar.DAY_OF_WEEK, Calendar.LONG, Locale.getDefault());
System.out.println("Weekday of birth: " + weekday); // wrong

Answer 1

1. > Calendar#set期望值按年、月、日期顺序
2. 日历 月份是基于0 的，而不是基于1 的。因此一月是 0 而不是 1(感谢 HovercraftFullOfEels)

您应该避免使用 String 解析这些类型的问题，而是使用自定义 DateFormat 来解析输入的 String 然后 utalise Calendar 类

try {
    Scanner s = new Scanner(System.in);
    System.out.println("Please enter your birthday. Format: DD.MM.YYYY");
    String bday = s.nextLine();

    Date date = new SimpleDateFormat("dd.MM.yyyy").parse(bday);

    Calendar birthday = Calendar.getInstance();
    birthday.setTime(date);
    String weekday = birthday.getDisplayName(Calendar.DAY_OF_WEEK, Calendar.LONG, Locale.getDefault());
    System.out.println("Weekday of birth: " + weekday); // wrong    }
} catch (ParseException exp) {
    exp.printStackTrace();
}

对于 24.11.2015 的输入，输出 Weekday of birth: Tuesday

当然，您可以简单地使用 Java 8 中的新时间 API，例如...

Scanner s = new Scanner(System.in);
System.out.println("Please enter your birthday. Format: DD.MM.YYYY");
String bday = s.nextLine();

LocalDate ld = LocalDate.parse(bday, DateTimeFormatter.ofPattern("dd.MM.yyyy"));
System.out.println("DayOfWeek = " + ld.getDayOfWeek().getDisplayName(TextStyle.FULL, Locale.getDefault()));