diff --git a/core-java-8/src/main/java/com/baeldung/timezonedisplay/TimezoneDisplay.java b/core-java-8/src/main/java/com/baeldung/timezonedisplay/TimezoneDisplay.java new file mode 100644 index 0000000000..ff618c8eea --- /dev/null +++ b/core-java-8/src/main/java/com/baeldung/timezonedisplay/TimezoneDisplay.java @@ -0,0 +1,55 @@ +package com.baeldung.timezonedisplay; + +import java.time.LocalDateTime; +import java.time.ZoneId; +import java.time.ZoneOffset; +import java.util.Comparator; +import java.util.List; +import java.util.Set; +import java.util.stream.Collectors; + +public class TimezoneDisplay { + + public enum OffsetBase { + GMT, UTC + } + + public List compileListFor(OffsetBase base) { + Set availableZoneIds = ZoneId.getAvailableZoneIds(); + + LocalDateTime now = LocalDateTime.now(); + return availableZoneIds + .stream() + .map(ZoneId::of) + .sorted(new ZoneComparator()) + .map(id -> String.format("(%s%s) %s", base, getOffset(now, id), id.getId())) + .collect(Collectors.toList()); + } + + private String getOffset(LocalDateTime dateTime, ZoneId id) { + return dateTime + .atZone(id) + .getOffset() + .getId() + .replace("Z", "+00:00"); + } + + private class ZoneComparator implements Comparator { + + @Override + public int compare(ZoneId zoneId1, ZoneId zoneId2) { + LocalDateTime now = LocalDateTime.now(); + + ZoneOffset offset1 = now + .atZone(zoneId1) + .getOffset(); + + ZoneOffset offset2 = now + .atZone(zoneId2) + .getOffset(); + + return offset1.compareTo(offset2); + } + } + +} diff --git a/core-java-8/src/main/java/com/baeldung/timezonedisplay/TimezoneDisplayApp.java b/core-java-8/src/main/java/com/baeldung/timezonedisplay/TimezoneDisplayApp.java new file mode 100644 index 0000000000..42a7a2ba85 --- /dev/null +++ b/core-java-8/src/main/java/com/baeldung/timezonedisplay/TimezoneDisplayApp.java @@ -0,0 +1,19 @@ +package com.baeldung.timezonedisplay; + +import java.util.List; + +public class TimezoneDisplayApp { + + public static void main(String... args) { + TimezoneDisplay display = new TimezoneDisplay(); + + System.out.println("Time zones in UTC:"); + List utc = display.compileListFor(TimezoneDisplay.OffsetBase.UTC); + utc.forEach(System.out::println); + + System.out.println("Time zones in GMT:"); + List gmt = display.compileListFor(TimezoneDisplay.OffsetBase.GMT); + gmt.forEach(System.out::println); + } + +} diff --git a/core-java/src/main/java/com/baeldung/timezonedisplay/TimezoneDisplayJava7.java b/core-java/src/main/java/com/baeldung/timezonedisplay/TimezoneDisplayJava7.java new file mode 100644 index 0000000000..79f0729f32 --- /dev/null +++ b/core-java/src/main/java/com/baeldung/timezonedisplay/TimezoneDisplayJava7.java @@ -0,0 +1,43 @@ +package com.baeldung.timezonedisplay; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.List; +import java.util.TimeZone; +import java.util.concurrent.TimeUnit; + +public class TimezoneDisplayJava7 { + + public enum OffsetBase { + GMT, UTC + } + + public List compileListFor(TimezoneDisplayJava7.OffsetBase base) { + String[] availableZoneIds = TimeZone.getAvailableIDs(); + List result = new ArrayList<>(availableZoneIds.length); + + for (String zoneId : availableZoneIds) { + TimeZone curTimeZone = TimeZone.getTimeZone(zoneId); + + String offset = calculateOffset(curTimeZone.getRawOffset()); + + result.add(String.format("(%s%s) %s", base, offset, zoneId)); + } + + Collections.sort(result); + + return result; + } + + private String calculateOffset(int rawOffset) { + if (rawOffset == 0) { + return "+00:00"; + } + long hours = TimeUnit.MILLISECONDS.toHours(rawOffset); + long minutes = TimeUnit.MILLISECONDS.toMinutes(rawOffset); + minutes = Math.abs(minutes - TimeUnit.HOURS.toMinutes(hours)); + + return String.format("%+03d:%02d", hours, Math.abs(minutes)); + } + +} diff --git a/core-java/src/main/java/com/baeldung/timezonedisplay/TimezoneDisplayJava7App.java b/core-java/src/main/java/com/baeldung/timezonedisplay/TimezoneDisplayJava7App.java new file mode 100644 index 0000000000..8f0acb38f3 --- /dev/null +++ b/core-java/src/main/java/com/baeldung/timezonedisplay/TimezoneDisplayJava7App.java @@ -0,0 +1,23 @@ +package com.baeldung.timezonedisplay; + +import java.util.List; + +public class TimezoneDisplayJava7App { + + public static void main(String... args) { + TimezoneDisplayJava7 display = new TimezoneDisplayJava7(); + + System.out.println("Time zones in UTC:"); + List utc = display.compileListFor(TimezoneDisplayJava7.OffsetBase.UTC); + for (String timeZone : utc) { + System.out.println(timeZone); + } + + System.out.println("Time zones in GMT:"); + List gmt = display.compileListFor(TimezoneDisplayJava7.OffsetBase.GMT); + for (String timeZone : gmt) { + System.out.println(timeZone); + } + } + +}