Convert Calendar to LocalDate

Question

I decided to upgrade from 5.5 to Optaplanner 7.5 Nurseroster but have run into a number of silly issues. Below is one. The routine I previously used is below. Now however the new version requires LocalDate. I have an MySql database back-end and the users select the roster schedule planner via a calendar. Any suggestions will be appreciated.

int shiftDateSize = maxDayIndex + 1;
        List<ShiftDate> shiftDateList = new ArrayList<ShiftDate>(shiftDateSize);
        //shiftDateMap = new HashMap<String, ShiftDate>(shiftDateSize);
        long id = 0L;
        int dayIndex = 0;
        calendar.setTime(startDate);
        for (int i = 0; i < shiftDateSize; i++) {
            ShiftDate shiftDate = new ShiftDate();
            shiftDate.setId(id);
            shiftDate.setDayIndex(dayIndex);
            **String dateString = dateFormat.format(calendar.getTime());**
            shiftDate.setDateString(dateString);
            **shiftDate.setDayOfWeek(DayOfWeek.valueOfCalendar(calendar.get(Calendar.DAY_OF_WEEK)));**
            shiftDate.setShiftList(new ArrayList<Shift>());
            shiftDateList.add(shiftDate);
            shiftDateMap.put(dateString, shiftDate);
            id++;
            dayIndex++;
            calendar.add(Calendar.DAY_OF_YEAR, 1);
        }
        nurseRoster.setShiftDateList(shiftDateList);
    } 

Balsam

Possible duplicate of Convert java.util.Date to java.time.LocalDate – Obverse

@Convert(converter = LocalDateTimeConverter.class) try it – Dutyfree

Answer 1

I have tried the following code to get the LocalDate from Calendar

Calendar calendar = Calendar.getInstance();
TimeZone tz = calendar.getTimeZone();
ZoneId zid = tz == null ? ZoneId.systemDefault() : tz.toZoneId();
LocalDate localDate = LocalDateTime.ofInstant(calendar.toInstant(), zid).LocalDate();

or simply in one line:

LocalDate localDate = LocalDateTime.ofInstant(calendar.toInstant(), calendar.getTimeZone().toZoneId()).toLocalDate();

I have followed these steps from this link Convert Calendar to LocalDateTime

Variolite

Answer 2

In Java 8 you can just do

LocalDateTime.ofInstant(cal.toInstant(), ZoneId.systemDefault())

Complainant

Answer 3

Java 9

import java.util.Calendar;
import java.time.LocalDate;
import java.time.ZoneId;

LocalDate.ofInstant(calendar.toInstant(), ZoneId.systemDefault());

Ratchford

Android requires API 34 for this. – Muskogee

Answer 4

The following code probably works too.

Calendar cal = Calendar.getInstance();
Date input = cal.getTime();
LocalDate da = input.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();

This first gets the date in Date type and then converts it to LocalDate format as far as I know.

Spore

Answer 5

If you're reading the LocalDate(Time) from your SQL database and is the only API connection point (so Calendar isn't exposed anywhere), then don't use Calendar at all.

Use a Hibernate/JPA or JDBC version that supports LocalDate(Time) and read that directly from the database. They've been supporting it for years, but your hibernate/JPA or JDBC version connecting to MySQL might be older.

It is error prone to read a date from the database as a Calendar and then convert the Calendar into a LocalDate(Time). java.util.Calendar is inherently broken, that's why LocalDate(Time) was created. IIRC, errors included dependence on OS settings (timezone, DST rules, etc), making it's behavior machine dependent.

If Calendar is exposed in your API, then this answer won't work, of course.

Vedavedalia

Since Hibernate supported LocalDate other features regarding java.util.Date are broken. This is not funny: hibernate.atlassian.net/browse/HHH-11875 – Xenocryst