Jonathan Cook
70 lines
2.7 KiB
Java
70 lines
2.7 KiB
Java
package com.baeldung.dst;
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import static org.assertj.core.api.Assertions.assertThat;
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import java.text.DateFormat;
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import java.text.ParseException;
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import java.text.SimpleDateFormat;
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import java.util.Calendar;
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import java.util.Date;
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import java.util.Locale;
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import java.util.TimeZone;
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import org.junit.Ignore;
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import org.junit.Test;
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public class DaylightSavingTimeExamplesUnitTest {
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@Test
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public void givenItalianTimeZone_WhenDSTHappens_ThenCorrectlyShiftTimeZone() throws ParseException {
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TimeZone.setDefault(TimeZone.getTimeZone("Europe/Rome"));
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TimeZone tz = TimeZone.getTimeZone("Europe/Rome");
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Calendar cal = Calendar.getInstance(tz, Locale.ITALIAN);
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DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm", Locale.ITALIAN);
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Date dateBeforeDST = df.parse("2018-03-25 01:55");
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prettyPrint(cal.getTimeZone());
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cal.setTime(dateBeforeDST);
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System.out.println("Before DST (00:55 UTC - 01:55 GMT+1) = " + dateBeforeDST);
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System.out.println("With this Calendar " + (cal.get(Calendar.ZONE_OFFSET) + cal.get(Calendar.DST_OFFSET)) / (60 * 1000) + " minutes must be added to UTC (GMT TimeZone) to get a correct date for this TimeZone\n");
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assertThat(cal.get(Calendar.ZONE_OFFSET)).isEqualTo(3600000);
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assertThat(cal.get(Calendar.DST_OFFSET)).isEqualTo(0);
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cal.add(Calendar.MINUTE, 10);
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Date dateAfterDST = cal.getTime();
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System.out.println(" After DST (01:05 UTC - 03:05 GMT+2) = " + dateAfterDST);
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System.out.println("With this Calendar " + (cal.get(Calendar.ZONE_OFFSET) + cal.get(Calendar.DST_OFFSET)) / (60 * 1000) + " minutes must be added to UTC (GMT TimeZone) to get a correct date for this TimeZone\n");
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assertThat(cal.get(Calendar.DST_OFFSET)).isEqualTo(3600000);
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assertThat(dateAfterDST).isEqualTo(df.parse("2018-03-25 03:05"));
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Long deltaBetweenDatesInMillis = dateAfterDST.getTime() - dateBeforeDST.getTime();
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Long tenMinutesInMillis = (1000L * 60 * 10);
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assertThat(deltaBetweenDatesInMillis).isEqualTo(tenMinutesInMillis);
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}
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private void prettyPrint(TimeZone tz) {
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//@formatter:off
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System.out.println(String.format(
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" Zone ID = %s (%s)\n"
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+ " RawOffset = %s minutes\n"
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+ " DST = %s minutes\n"
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+ " -----------------------------------------",
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tz.getID(), tz.getDisplayName(), tz.getRawOffset()/60000, tz.getDSTSavings()/60000));
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//@formatter:on
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}
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@Test
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@Ignore
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public void whenIterating_ThenPrintAllTimeZones() {
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for (String id : TimeZone.getAvailableIDs()) {
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TimeZone tz = TimeZone.getTimeZone(id);
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prettyPrint(tz);
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}
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}
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}
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