First cut for basics of java 8 date time api

core-java-8/src/main/java/com/baeldung/datetime/UseDuration.java

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+package com.baeldung.datetime;
+
+import java.time.Duration;
+import java.time.LocalTime;
+import java.time.Period;
+
+public class UseDuration {
+    
+    public LocalTime modifyDates(LocalTime localTime,Duration duration){
+        return localTime.plus(duration);
+    }
+    
+    public Duration getDifferenceBetweenDates(LocalTime localTime1,LocalTime localTime2){
+        return Duration.between(localTime1, localTime2);
+    }
+}

core-java-8/src/main/java/com/baeldung/datetime/UseLocalDate.java

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+package com.baeldung.datetime;
+
+import java.time.DayOfWeek;
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.temporal.ChronoUnit;
+import java.time.temporal.TemporalAdjusters;
+
+public class UseLocalDate {
+    
+    public LocalDate getLocalDateUsingFactoryOfMethod(int year, int month, int dayOfMonth){        
+        return LocalDate.of(year, month, dayOfMonth);
+    }
+    
+    public LocalDate getLocalDateUsingParseMethod(String representation){        
+        return LocalDate.parse(representation);
+    }
+    
+    public LocalDate getLocalDateFromClock(){        
+        LocalDate localDate = LocalDate.now();
+        return localDate;
+    }
+    
+    public LocalDate getNextDay(LocalDate localDate){       
+        return localDate.plusDays(1);
+    }
+    
+    public LocalDate getPreviousDay(LocalDate localDate){        
+        return localDate.minus(1, ChronoUnit.DAYS);
+    }
+    
+    public DayOfWeek getDayOfWeek(LocalDate localDate){        
+        DayOfWeek day = localDate.getDayOfWeek();
+        return day;
+    }
+    
+    public LocalDate getFirstDayOfMonth(){        
+        LocalDate firstDayOfMonth = LocalDate.now().with(TemporalAdjusters.firstDayOfMonth());
+        return firstDayOfMonth;
+    }
+    
+    public LocalDateTime getStartOfDay(LocalDate localDate){        
+        LocalDateTime startofDay = localDate.atStartOfDay();
+        return startofDay;
+    }
+}

core-java-8/src/main/java/com/baeldung/datetime/UseLocalDateTime.java

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+package com.baeldung.datetime;
+
+import java.time.LocalDateTime;
+
+public class UseLocalDateTime {
+    
+    public LocalDateTime getLocalDateTimeUsingParseMethod(String representation){        
+        return LocalDateTime.parse(representation);
+    }
+
+}

core-java-8/src/main/java/com/baeldung/datetime/UseLocalTime.java

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+package com.baeldung.datetime;
+
+import java.time.LocalTime;
+import java.time.temporal.ChronoUnit;
+
+public class UseLocalTime {
+    
+    public LocalTime getLocalTimeUsingFactoryOfMethod(int hour, int min, int seconds){        
+        LocalTime localTime = LocalTime.of(hour, min, seconds);
+        return localTime;
+    }
+    
+    public LocalTime getLocalTimeUsingParseMethod(String timeRepresentation){        
+        LocalTime localTime = LocalTime.parse(timeRepresentation);
+        return localTime;
+    }
+    
+    public LocalTime getLocalTimeFromClock(){        
+        LocalTime localTime = LocalTime.now();
+        return localTime;
+    }
+    
+    public LocalTime addAnHour(LocalTime localTime){
+        LocalTime newTime = localTime.plus(1,ChronoUnit.HOURS);
+        return newTime;
+    }
+    
+    public int getHourFromLocalTime(LocalTime localTime){        
+        return localTime.getHour();
+    }
+    
+    public LocalTime getLocalTimeWithMinuteSetToValue(LocalTime localTime, int minute){        
+        return localTime.withMinute(minute);
+    }
+}

core-java-8/src/main/java/com/baeldung/datetime/UsePeriod.java

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+package com.baeldung.datetime;
+
+import java.time.LocalDate;
+import java.time.Period;
+
+public class UsePeriod {
+    
+    public LocalDate modifyDates(LocalDate localDate,Period period){
+        return localDate.plus(period);
+    }
+    
+    public Period getDifferenceBetweenDates(LocalDate localDate1,LocalDate localDate2){
+        return Period.between(localDate1, localDate2);
+    }
+}

core-java-8/src/main/java/com/baeldung/datetime/UseToInstant.java

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+package com.baeldung.datetime;
+
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.util.Calendar;
+import java.util.Date;
+
+public class UseToInstant {
+    
+    public LocalDateTime convertDateToLocalDate(Date date){
+        LocalDateTime localDateTime = LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault());
+        return localDateTime;
+    }
+    
+    public LocalDateTime convertDateToLocalDate(Calendar calendar){
+        LocalDateTime localDateTime = LocalDateTime.ofInstant(calendar.toInstant(), ZoneId.systemDefault());
+        return localDateTime;
+    }
+}

core-java-8/src/main/java/com/baeldung/datetime/UseZonedDateTime.java

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+package com.baeldung.datetime;
+
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+
+public class UseZonedDateTime {
+    
+    public ZonedDateTime getZonedDateTime(LocalDateTime localDateTime,ZoneId zoneId){        
+        ZonedDateTime zonedDateTime = ZonedDateTime.of(localDateTime, zoneId);
+        return zonedDateTime;
+    }
+}

core-java-8/src/test/java/com/baeldung/datetime/UseLocalDateTest.java

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+package com.baeldung.datetime;
+
+import java.time.DayOfWeek;
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.Month;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class UseLocalDateTest {
+    
+    UseLocalDate useLocalDate = new UseLocalDate();
+    
+    @Test
+    public void givenValues_whenUsingFactoryOf_thenLocalDate(){
+        Assert.assertEquals("2016-05-10",useLocalDate.getLocalDateUsingFactoryOfMethod(2016,5,10).toString());
+    }
+    
+    @Test
+    public void givenString_whenUsingParse_thenLocalDate(){
+        Assert.assertEquals("2016-05-10",useLocalDate.getLocalDateUsingParseMethod("2016-05-10").toString());
+    }
+    
+    @Test
+    public void whenUsingClock_thenLocalDate(){
+        Assert.assertEquals(LocalDate.now(),useLocalDate.getLocalDateFromClock());
+    }
+    
+    @Test
+    public void givenDate_whenUsingPlus_thenNextDay(){
+        Assert.assertEquals(LocalDate.now().plusDays(1),useLocalDate.getNextDay(LocalDate.now()));
+    }
+    
+    @Test
+    public void givenDate_whenUsingMinus_thenPreviousDay(){
+        Assert.assertEquals(LocalDate.now().minusDays(1),useLocalDate.getPreviousDay(LocalDate.now()));
+    }
+    
+    @Test
+    public void givenToday_whenUsingGetDayOfWeek_thenDayOfWeek(){
+        Assert.assertEquals(DayOfWeek.SUNDAY,useLocalDate.getDayOfWeek(LocalDate.parse("2016-05-22")));
+    }
+    
+    @Test
+    public void givenToday_whenUsingWithTemporalAdjuster_thenFirstDayOfMonth(){
+        Assert.assertEquals(1,useLocalDate.getFirstDayOfMonth().getDayOfMonth());
+    }
+    
+    @Test
+    public void givenLocalDate_whenUsingAtStartOfDay_thenReturnMidnight(){
+        Assert.assertEquals(LocalDateTime.parse("2016-05-22T00:00:00"),useLocalDate.getStartOfDay(LocalDate.parse("2016-05-22")));
+    }
+
+}

core-java-8/src/test/java/com/baeldung/datetime/UseLocalDateTimeTest.java

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+package com.baeldung.datetime;
+
+import java.time.LocalDate;
+import java.time.LocalTime;
+import java.time.Month;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class UseLocalDateTimeTest {
+    
+    UseLocalDateTime useLocalDateTime = new UseLocalDateTime();
+    
+    @Test
+    public void givenString_whenUsingParse_thenLocalDateTime(){
+        Assert.assertEquals(LocalDate.of(2016, Month.MAY, 10),useLocalDateTime.getLocalDateTimeUsingParseMethod("2016-05-10T06:30").toLocalDate());
+        Assert.assertEquals(LocalTime.of(6,30),useLocalDateTime.getLocalDateTimeUsingParseMethod("2016-05-10T06:30").toLocalTime());
+    }
+}

core-java-8/src/test/java/com/baeldung/datetime/UseLocalTimeTest.java

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+package com.baeldung.datetime;
+
+import java.time.LocalTime;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class UseLocalTimeTest {
+    
+    UseLocalTime useLocalTime = new UseLocalTime();
+    
+    @Test
+    public void givenValues_whenUsingFactoryOf_thenLocalTime(){
+        Assert.assertEquals("07:07:07",useLocalTime.getLocalTimeUsingFactoryOfMethod(7,7,7).toString());
+    }
+    
+    @Test
+    public void givenString_whenUsingParse_thenLocalTime(){
+        Assert.assertEquals("06:30",useLocalTime.getLocalTimeUsingParseMethod("06:30").toString());
+    }
+    
+    @Test
+    public void givenTime_whenAddHour_thenLocalTime(){
+        Assert.assertEquals("07:30",useLocalTime.addAnHour(LocalTime.of(6,30)).toString());
+    }
+    
+    @Test
+    public void getHourFromLocalTime(){
+        Assert.assertEquals(1, useLocalTime.getHourFromLocalTime(LocalTime.of(1,1)));
+    }
+    
+    @Test
+    public void getLocalTimeWithMinuteSetToValue(){
+        Assert.assertEquals(LocalTime.of(10, 20), useLocalTime.getLocalTimeWithMinuteSetToValue(LocalTime.of(10,10), 20));
+    }
+}

core-java-8/src/test/java/com/baeldung/datetime/UsePeriodTest.java

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+package com.baeldung.datetime;
+
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.Period;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class UsePeriodTest {
+    UsePeriod usingPeriod=new UsePeriod();
+    
+    @Test
+    public void givenPeriodAndLocalDate_thenCalculateModifiedDate(){
+        Period period = Period.ofDays(1);
+        LocalDate localDate = LocalDate.parse("2007-05-10");
+        Assert.assertEquals(localDate.plusDays(1),usingPeriod.modifyDates(localDate, period));
+    }
+    
+    @Test
+    public void givenDates_thenGetPeriod(){
+        LocalDate localDate1 = LocalDate.parse("2007-05-10");
+        LocalDate localDate2 = LocalDate.parse("2007-05-15");
+        
+        Assert.assertEquals(Period.ofDays(5), usingPeriod.getDifferenceBetweenDates(localDate1, localDate2));
+    }
+}

core-java-8/src/test/java/com/baeldung/datetime/UseZonedDateTimeTest.java

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+package com.baeldung.datetime;
+
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class UseZonedDateTimeTest {
+    
+    UseZonedDateTime zonedDateTime=new UseZonedDateTime();
+    
+    @Test
+    public void givenZoneId_thenZonedDateTime(){
+        ZoneId zoneId=ZoneId.of("Europe/Paris");
+        ZonedDateTime zonedDatetime=zonedDateTime.getZonedDateTime(LocalDateTime.parse("2016-05-20T06:30"), zoneId);
+        Assert.assertEquals(zoneId,ZoneId.from(zonedDatetime));
+    }
+}