I made a method to ask for Premium Friday (Java 8 version)

First draft

I read I made a method to find Premium Friday and wrote a Java 8 version for studying Java 8.

import java.time.*;
import java.time.format.DateTimeFormatter;

public class PremiumFriday {

    public static void main(String[] args) {

        int[] years = {2017, 2018, 2019};
        for (int year : years) {
            for (int month = 1; month < 13; month++) {
                if (year == 2017 && month == 1) {
                    continue;
                }
                YearMonth ym = YearMonth.of(year, month);
                LocalDateTime pf = getMonthOfPremiumFriday(ym);
                System.out.println(DateTimeFormatter.ofPattern("yyyy/MM/dd(E)").format(pf));
            }
        }
    }

    private static LocalDateTime getMonthOfPremiumFriday(YearMonth ym) {

        LocalDate ls = ym.atEndOfMonth();
        LocalDateTime ldt = ls.atStartOfDay();

        while (true) {
            if (ldt.getDayOfWeek() == DayOfWeek.FRIDAY) {
                break;
            } else {
                ldt = ldt.plusDays(-1);
            }
        }

        return ldt;

    }

}

result

2017/02/24(Money)
2017/03/31(Money)
2017/04/28(Money)
2017/05/26(Money)
2017/06/30(Money)
2017/07/28(Money)
2017/08/25(Money)
2017/09/29(Money)
2017/10/27(Money)
2017/11/24(Money)
2017/12/29(Money)
2018/01/26(Money)
2018/02/23(Money)
2018/03/30(Money)
2018/04/27(Money)
2018/05/25(Money)
2018/06/29(Money)
2018/07/27(Money)
2018/08/31(Money)
2018/09/28(Money)
2018/10/26(Money)
2018/11/30(Money)
2018/12/28(Money)
2019/01/25(Money)
2019/02/22(Money)
2019/03/29(Money)
2019/04/26(Money)
2019/05/31(Money)
2019/06/28(Money)
2019/07/26(Money)
2019/08/30(Money)
2019/09/27(Money)
2019/10/25(Money)
2019/11/29(Money)
2019/12/27(Money)

It's simple and easy to understand when I write it, but it was hard to find out that I needed to update my knowledge ...

2017/3/2 postscript

I received advice on how to write on Twitter, so I rewrote it.

import java.time.*;
import java.time.format.DateTimeFormatter;
import java.time.temporal.TemporalAdjusters;

public class PremiumFriday {

    public static void main(String[] args) {

        int[] years = {2017, 2018, 2019};
        for (int year : years) {
            for (Month month : Month.values()) {
                if (year == 2017 && month == Month.JANUARY) {
                    continue;
                }
                YearMonth ym = YearMonth.of(year, month);
                LocalDate pf = getMonthOfPremiumFriday(ym);
                System.out.println(DateTimeFormatter.ofPattern("yyyy/MM/dd(E)").format(pf));
            }
        }
    }

    private static LocalDate getMonthOfPremiumFriday(YearMonth ym) {

        LocalDate premiumFriday = ym.atEndOfMonth().with(TemporalAdjusters.lastInMonth(DayOfWeek.FRIDAY));

        return premiumFriday;

    }

}

point

1. Use Month \ (Java Platform SE 8 ) for the month loop condition Changed to.
2. Use TemporalAdjusters \ (Java Platform SE 8 ) to judge the last Friday I changed it to use.
3. See also LocalDate \ (Java Platform SE 8 ) for how to use it.
4. For how to write using a lambda expression, refer to the description of another person (this article is linked from the following article). I don't dare to use lambda so that I can see what I'm doing in parts in the future.

Message to yourself in the future

If I have a chance to use Java 8 at work, I will definitely do this once, so I will search on Qiita!