Get one letter abbreviation of week day of a date in java

问题

As far I know, in Java I can get weekdays in normal (Friday) or short mode (Fri). But, there is any way to obtain only first letter?

I thought I can get first letter using "substring", but it won't be correct for all languages. For example, spanish weekdays are: Lunes, Martes, Miércoles, Jueves, Viernes, Sábado and Domingo, and first letter for "Miércoles" is X instead of M to difference it from "Martes".

回答1:

In Android you can use SimpleDateFormat with "EEEEE". In the next example you can see it.

SimpleDateFormat formatLetterDay = new SimpleDateFormat("EEEEE",Locale.getDefault());
String letter = formatLetterDay.format(new Date());

回答2:

As mentioned above there is no standard Java support for this. Using the formatting string "EEEEE" however is not guaranteed to work on all Android devices. The following code is guaranteed to work on any device:

public String firstLetterOfDayOfTheWeek(Date date) {

    Locale locale = Locale.getDefault(); 
    DateFormat weekdayNameFormat = new SimpleDateFormat("EEE", locale); 
    String weekday = weekdayNameFormat.format(date); 
    return weekday.charAt(0)+""; 
}

回答3:

There is no standard Java API support for doing that.

Part of the reason is that many (maybe even most) languages don't have conventional unique one-letter weekday abbreviations. In English there isn't, for example (M T W T F S S).

A (hypothetical) formatting option that doesn't work¹ in many / most locales would be an impediment to internationalization rather than a help.

^{1 - I mean this in the human sense. You could invent a convention, but people wouldn't understand what the abbreviations meant.}

回答4:

I realize the OP was asking for standards across languages, and this does not address it. But there is/was a standard for using single character Day of Week abbreviation.

Back in mainframe days, using a 1-character abbreviation for Day of Week was common, either to store day of week in 1 character field (to save precious space), or have a report heading for single-character column. The "standard" was to use MTWRFSU, where R was for Thursday, and U for Sunday.

I could not find any definitive references to this (which is why I quoted "standard", but here are a couple of examples: http://eventguide.com/topics/one_digit_day_abbreviations.html http://www.registrar.ucla.edu/soc/definitions.htm#Anchor-Days-3800