package com.baeldung.convert; import org.joda.time.Instant; import org.junit.Assert; import org.junit.Test; import java.time.LocalDateTime; import java.time.ZoneId; import java.time.ZonedDateTime; import java.util.Calendar; import java.util.Date; public class ConvertDateTimeUnitTest { public final long millis = 1556175797428L; @Test public void givenLocalDateTime_WhenToEpochMillis_ThenMillis() { ZoneId id = ZoneId.systemDefault(); LocalDateTime localDateTime = LocalDateTime.ofInstant(java.time.Instant.ofEpochMilli(millis), id); ZonedDateTime zdt = ZonedDateTime.of(localDateTime, id); Assert.assertEquals(millis, zdt.toInstant().toEpochMilli()); } @Test public void givenJava8Instant_WhenGToEpochMillis_ThenMillis() { java.time.Instant instant = java.time.Instant.ofEpochMilli(millis); Assert.assertEquals(millis, instant.toEpochMilli()); } @Test public void givenDate_WhenGetTime_ThenMillis() { Date date = new Date(millis); Assert.assertEquals(millis, date.getTime()); } @Test public void givenCalendar_WhenGetTimeInMillis_ThenMillis() { Calendar calendar = Calendar.getInstance(); calendar.setTime(new Date(millis)); Assert.assertEquals(millis, calendar.getTimeInMillis()); } @Test public void givenJodaInstant_WhenGetMillis_ThenMillis() { Instant jodaInstant = Instant.ofEpochMilli(millis); Assert.assertEquals(millis, jodaInstant.getMillis()); } @Test public void givenJODADateTime_WhenGetMillis_ThenMillis() { org.joda.time.DateTime jodaDateTime = new org.joda.time.DateTime(millis); Assert.assertEquals(millis, jodaDateTime.getMillis()); } }