Find name of day by year, month and day [duplicate]

This question already has answers here: How to determine day of week by passing specific date? 开发者_运维百科 (28 answers) Closed 8 years ago.

If I have int year, int month, int day in Java, how to find name of day ? Is there already some functions for this ?

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Use SimpleDateFormat with a pattern of EEEE to get the name of the day of week.

// Assuming that you already have this.
int year = 2011;
int month = 7;
int day = 22;

// First convert to Date. This is one of the many ways.
String dateString = String.format("%d-%d-%d", year, month, day);
Date date = new SimpleDateFormat("yyyy-M-d").parse(dateString);

// Then get the day of week from the Date based on specific locale.
String dayOfWeek = new SimpleDateFormat("EEEE", Locale.ENGLISH).format(date);

System.out.println(dayOfWeek); // Friday

Here it is wrapped all up into a nice Java class for you.

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;


public class DateUtility
{

    public static void main(String args[]){
        System.out.println(dayName("2015-03-05 00:00:00", "YYYY-MM-DD HH:MM:ss"));
    }

    public static String dayName(String inputDate, String format){
        Date date = null;
        try {
            date = new SimpleDateFormat(format).parse(inputDate);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return new SimpleDateFormat("EEEE", Locale.ENGLISH).format(date);
    }
}

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You can do something like this to get the names of the days of the week for different locales.

Here's the important part:

DateFormatSymbols dfs = new DateFormatSymbols(usersLocale);
String weekdays[] = dfs.getWeekdays();

That can be combined with this:

Calendar cal = Calendar.getInstance();
int day = cal.get(Calendar.DAY_OF_WEEK);

To get what you're looking for:

String nameOfDay = weekdays[day];

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Construct a GregorianCalendar with the year, month and day, then query it to find the name of the day. Something like this:

int year = 1977;
int month = 2;
int dayOfMonth = 15;
Calendar myCalendar = new GregorianCalendar(year, month, dayOfMonth);

int dayOfWeek = myCalendar.get(Calendar.DAY_OF_WEEK);

Note that the day of week is returned as an int representing the ordinal of the day in the locale's week day representation. IE, in a locale where the weekday starts on Monday and ends on Sunday, a 2 would represent Tuesday, whereas if the locale weekday starts on Sunday then that same 2 would represent Monday.

Edit

And since there is alot of answer editing going on, allow me to add the following:

DateFormatSymbols symbols = new DateFormatSymbols(Locale.getDefault());
String dayOfMonthStr = symbols.getWeekdays()[dayOfMonth];

Thought to be honest, I like the SimpleDateFormatter approach better, because it encapsulates the very same code as I've shown above. Silly me to forget all about it.

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You can use the Calendar Object to find this.

Once you create the calendar instance you get the DAY_OF_WEEK (which is an int) then you can find the day from there)

You can use a switch statement like so:

import java.util.*;

public class DayOfWeek {

    public static void main(String[] args) {
        Calendar cal = Calendar.getInstance();
        int day = cal.get(Calendar.DAY_OF_WEEK);
        System.out.print("Today is ");
        switch (day) {
            case 1:
                System.out.print("Sunday");
                break;
            case 2:
                System.out.print("Monday");
                break;
            case 3:
                System.out.print("Tuesday");
                break;
            case 4:
                System.out.print("Wednesday");
                break;
            case 5:
                System.out.print("Thursday");
                break;
            case 6:
                System.out.print("Friday");
                break;
            case 7:
                System.out.print("Saturday");
        }
        System.out.print(".");
    }
}

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The name of the week day differs per locale. So you have to use a DateFormat with the proper locale. For example:

SimpleDateFormat format = new SimpleDateFormat("EEEE");
System.out.println(format.format(date));

The Date object can be obtained in multiple ways, including the deprecated Date(..) constructor, the Calendar.set(..) methods or joda-time DateTime. (for the latter you can use joda-time's own DateTimeFormat)

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Calendar cal = Calendar.getInstance();
cal.set(Calendar.DAY_OF_MONTH, 22); //Set Day of the Month, 1..31
cal.set(Calendar.MONTH,6); //Set month, starts with JANUARY = 0
cal.set(Calendar.YEAR,2011); //Set year
System.out.println(cal.get(Calendar.DAY_OF_WEEK)); //Starts with Sunday, 6 = friday

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This kind of date-time work is easier when using the Joda-Time library. A simple one-liner.

String dayOfWeek = new LocalDate( 2014, 1, 2 ).dayOfWeek().getAsText( java.util.Locale.ENGLISH );

System.out.println( "dayOfWeek: " + dayOfWeek );

When run…

dayOfWeek: Thursday

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new GregorianCalendar().setTime(new Date()).get(DAY_OF_WEEK)

That gives you a number, Calendar.SUNDAY == 1, Calendar.MONDAY == 2, ...

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Yes, but it's a rather long process with the JDK. JodaTime may be a better choice (I haven't used it).

First, you get a Calendar object, so that you can construct a date from day/month/year/timezone. Do not use one of the deprecated Date constructors.

Then get a Date object from that calendar, and pass it to SimpleDateFormat. Note that the format objects are not threadsafe.

  // by default, this Calendar object will have the current timezone
  Calendar cal = GregorianCalendar.getInstance();
  cal.set(2011, 6, 22);

  // this formatter will have the current locale
  SimpleDateFormat format = new SimpleDateFormat("EEEE");

  System.out.println(format.format(cal.getTime()));