How to Get first date and last date from given month in java? [duplicate]

Question

We will pass month information in yyyyMM format.From that given input how i will get FirstDate and LastDate of that month?

Input:-202002

OutPut Should be:-

First Date:- 2020-02-01,
Last Date:- 2020-02-29

DateFormat dateFormat = new SimpleDateFormat("yyyyMM");
Date date = new Date();
System.out.println("First Date:- "+dateFormat.format(date));    
Calendar calendar = Calendar.getInstance();
calendar.add(Calendar.MONTH, -1);
Date previousmonth = calendar.getTime();
System.out.println("LastDate:-"+dateFormat.format(previousmonth).toString());

Do you mean day instead of date? Because the first date of every month is 1 and the last of most is 31, 30 or 28. — Mick Vader
– Mick Vader, Commented Feb 20, 2020 at 10:22
Prefer to use java.util.time classes. The YearMonth class provides an easy atEndOfMonth() method. As for the first date of the month, it's the 1st. Just use atDay(1) — kumesana
– kumesana, Commented Feb 20, 2020 at 10:22
@kumesana there's no such thing as java.util.time. I think you mean java.time. — DodgyCodeException
– DodgyCodeException, Commented Feb 20, 2020 at 10:35

Jan Held · Accepted Answer · 2020-02-20 10:35:02Z

2

As I just learned, there are now special methods for it.

You can do it like this now:

public static final DateTimeFormatter FORMATTER = DateTimeFormatter.ofPattern("yyyyMM");
public static final DateTimeFormatter OUT_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd");

public static LocalDate[] getFirstAndLastDateOfMonthNew(String yearAndMonth) {
    final LocalDate[] result = new LocalDate[2];
    final YearMonth yearMonth = YearMonth.parse(yearAndMonth, FORMATTER);
    result[0] = yearMonth.atDay(1);
    result[1] = yearMonth.atEndOfMonth();;
    return result;
}

The old way would have been:

Just add the 01 to the date and parse it. The add a month and subtract a day.

public static final DateTimeFormatter FORMATTER = DateTimeFormatter.ofPattern("yyyyMMdd");
public static final DateTimeFormatter OUT_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd");

public static LocalDate[] getFirstAndLastDateOfMonth(String yearAndMonth) {
    final LocalDate[] result = new LocalDate[2];
    final LocalDate first = LocalDate.parse(yearAndMonth + "01", FORMATTER);
    final LocalDate last = first.plusMonths(1).minusDays(1);
    result[0] = first;
    result[1] = last;
    return result;
}

edited Feb 20, 2020 at 10:35

answered Feb 20, 2020 at 10:26

Jan Held

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2 Comments

kumesana Over a year ago

... Or, like, use YearMonth

Jan Held Over a year ago

Yep, just learned that. Thank you. I updated my answer.

Coma · Accepted Answer · 2020-02-20 14:59:23Z

1

try this, you can do it simply with LocalDate

String date = "202002";

DateTimeFormatter formatter = new DateTimeFormatterBuilder()
                                .appendPattern("yyyyMM")
                                .parseDefaulting(ChronoField.DAY_OF_MONTH, 1)
                                .toFormatter();

LocalDate firstDay = LocalDate.parse(date, formatter);
LocalDate lastDay = firstDay.withDayOfMonth(firstDay.getMonth().length(firstDay.isLeapYear()));

answered Feb 20, 2020 at 14:59

Coma

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Comments

fathy elshemy · Accepted Answer · 2020-02-20 11:16:36Z

0

You can use java 8 capabilities like TemporalAdjusters I think it May help you in your problem like the following

    public static void getFirstDayAndLastDayInMonth(String date){
        LocalDate monthOfYear=LocalDate.parse(new String(date+"01"),DateTimeFormatter.BASIC_ISO_DATE);
        LocalDate firstLocalDate=monthOfYear.with(TemporalAdjusters.firstDayOfMonth());
        System.out.println(firstLocalDate);
        LocalDate lastLocalDate=monthOfYear.with(TemporalAdjusters.lastDayOfMonth());
        System.out.println(lastLocalDate);
    }

input 202002

output

2020-02-01
2020-02-29

and you can follow the following doc it's a good start to learn more

answered Feb 20, 2020 at 11:16

fathy elshemy

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