java-tutorials/java-dates/src/test/java/com/baeldung/date/DateWithoutTimeUnitTest.java

package com.baeldung.date;

import org.junit.Assert;
import org.junit.Test;

import java.text.ParseException;
import java.time.LocalDate;
import java.time.OffsetDateTime;
import java.util.Calendar;
import java.util.Date;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotEquals;

public class DateWithoutTimeUnitTest {

    private static final long MILLISECONDS_PER_DAY = 24 * 60 * 60 * 1000;

    @Test
    public void whenGettingDateWithoutTimeUsingCalendar_thenReturnDateWithoutTime() {
        Date dateWithoutTime = DateWithoutTime.getDateWithoutTimeUsingCalendar();

        // first check the time is set to 0
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(dateWithoutTime);

        assertEquals(0, calendar.get(Calendar.HOUR_OF_DAY));
        assertEquals(0, calendar.get(Calendar.MINUTE));
        assertEquals(0, calendar.get(Calendar.SECOND));
        assertEquals(0, calendar.get(Calendar.MILLISECOND));

        // we get the day of the date
        int day = calendar.get(Calendar.DAY_OF_MONTH);

        // if we add the mills of one day minus 1 we should get the same day
        calendar.setTimeInMillis(dateWithoutTime.getTime() + MILLISECONDS_PER_DAY - 1);
        assertEquals(day, calendar.get(Calendar.DAY_OF_MONTH));

        // if we add one full day in millis we should get a different day
        calendar.setTimeInMillis(dateWithoutTime.getTime() + MILLISECONDS_PER_DAY);
        assertNotEquals(day, calendar.get(Calendar.DAY_OF_MONTH));
    }

    @Test
    public void whenGettingDateWithoutTimeUsingFormat_thenReturnDateWithoutTime() throws ParseException {
        Date dateWithoutTime = DateWithoutTime.getDateWithoutTimeUsingFormat();

        // first check the time is set to 0
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(dateWithoutTime);

        assertEquals(0, calendar.get(Calendar.HOUR_OF_DAY));
        assertEquals(0, calendar.get(Calendar.MINUTE));
        assertEquals(0, calendar.get(Calendar.SECOND));
        assertEquals(0, calendar.get(Calendar.MILLISECOND));

        // we get the day of the date
        int day = calendar.get(Calendar.DAY_OF_MONTH);

        // if we add the mills of one day minus 1 we should get the same day
        calendar.setTimeInMillis(dateWithoutTime.getTime() + MILLISECONDS_PER_DAY - 1);
        assertEquals(day, calendar.get(Calendar.DAY_OF_MONTH));

        // if we add one full day in millis we should get a different day
        calendar.setTimeInMillis(dateWithoutTime.getTime() + MILLISECONDS_PER_DAY);
        assertNotEquals(day, calendar.get(Calendar.DAY_OF_MONTH));
    }

    @Test
    public void whenGettingLocalDate_thenReturnDateWithoutTime() {
        // get the local date
        LocalDate localDate = DateWithoutTime.getLocalDate();

        // get the millis of our LocalDate
        long millisLocalDate = localDate
          .atStartOfDay()
          .toInstant(OffsetDateTime
            .now()
            .getOffset())
          .toEpochMilli();

        Calendar calendar = Calendar.getInstance();
        // if we add the millis of one day minus 1 we should get the same day
        calendar.setTimeInMillis(millisLocalDate + MILLISECONDS_PER_DAY - 1);
        assertEquals(localDate.getDayOfMonth(), calendar.get(Calendar.DAY_OF_MONTH));

        // if we add one full day in millis we should get a different day
        calendar.setTimeInMillis(millisLocalDate + MILLISECONDS_PER_DAY);
        assertNotEquals(localDate.getDayOfMonth(), calendar.get(Calendar.DAY_OF_MONTH));
    }

}