Bael 1344 (#3068)

* BAEL-1344 add java8 convert methods date, localdate, localdatetime

* BAEL-1344 add java9 example

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

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+/**
+ * 
+ */
+package com.baeldung.datetime;
+
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.ZoneId;
+import java.util.Date;
+
+/**
+ * Class which shows different ways of converting java.util.Date into java.time.LocalDate.
+ * 
+ * @author abialas
+ *
+ */
+public class DateToLocalDateConverter {
+
+    public static LocalDate convertToLocalDateViaInstant(Date dateToConvert) {
+        return dateToConvert.toInstant()
+            .atZone(ZoneId.systemDefault())
+            .toLocalDate();
+    }
+
+    public static LocalDate convertToLocalDateViaSqlDate(Date dateToConvert) {
+        return new java.sql.Date(dateToConvert.getTime()).toLocalDate();
+    }
+
+    public static LocalDate convertToLocalDateViaMilisecond(Date dateToConvert) {
+        return Instant.ofEpochMilli(dateToConvert.getTime())
+            .atZone(ZoneId.systemDefault())
+            .toLocalDate();
+    }
+
+}

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

@@ -0,0 +1,35 @@
+/**
+ * 
+ */
+package com.baeldung.datetime;
+
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.util.Date;
+
+/**
+ * Class which shows different ways of converting java.util.Date into java.time.LocalDateTime. 
+ * 
+ * @author abialas
+ *
+ */
+public class DateToLocalDateTimeConverter {
+
+    public static LocalDateTime convertToLocalDateTimeViaInstant(Date dateToConvert) {
+        return dateToConvert.toInstant()
+            .atZone(ZoneId.systemDefault())
+            .toLocalDateTime();
+    }
+
+    public static LocalDateTime convertToLocalDateTimeViaSqlTimestamp(Date dateToConvert) {
+        return new java.sql.Timestamp(dateToConvert.getTime()).toLocalDateTime();
+    }
+
+    public static LocalDateTime convertToLocalDateTimeViaMilisecond(Date dateToConvert) {
+        return Instant.ofEpochMilli(dateToConvert.getTime())
+            .atZone(ZoneId.systemDefault())
+            .toLocalDateTime();
+    }
+
+}

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

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+/**
+ * 
+ */
+package com.baeldung.datetime;
+
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.util.Date;
+
+/**
+ * Class which shows different ways of converting java.time.LocalDateTime into java.util.Date. 
+ *  
+ * @author abialas
+ *
+ */
+public class LocalDateTimeToDateConverter {
+
+    public static Date convertToDateViaSqlTimestamp(LocalDateTime dateToConvert) {
+        return java.sql.Timestamp.valueOf(dateToConvert);
+    }
+
+    public static Date convertToDateViaInstant(LocalDateTime dateToConvert) {
+        return java.util.Date.from(dateToConvert.atZone(ZoneId.systemDefault())
+            .toInstant());
+    }
+
+}

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

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+/**
+ * 
+ */
+package com.baeldung.datetime;
+
+import java.time.LocalDate;
+import java.time.ZoneId;
+import java.util.Date;
+
+/**
+ * Class which shows different ways of converting java.time.LocalDate into java.util.Date. 
+ *  
+ * @author abialas
+ *
+ */
+public class LocalDateToDateConverter {
+
+    public static Date convertToDateViaSqlDate(LocalDate dateToConvert) {
+        return java.sql.Date.valueOf(dateToConvert);
+    }
+
+    public static Date convertToDateViaInstant(LocalDate dateToConvert) {
+        return java.util.Date.from(dateToConvert.atStartOfDay()
+            .atZone(ZoneId.systemDefault())
+            .toInstant());
+    }
+
+}

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

@@ -0,0 +1,72 @@
+/**
+ * 
+ */
+package com.baeldung.datetime;
+
+import static org.junit.Assert.assertEquals;
+
+import java.time.LocalDate;
+import java.time.temporal.ChronoField;
+import java.util.Calendar;
+import java.util.Date;
+
+import org.junit.Test;
+
+/**
+ * 
+ * JUnits for {@link DateToLocalDateConverter} class.
+ * 
+ * @author abialas
+ *
+ */
+public class DateToLocalDateConverterTest {
+
+    @Test
+    public void shouldReturn10thNovember2010WhenConvertViaInstant() {
+        // given
+        Calendar calendar = Calendar.getInstance();
+        calendar.set(2010, 10, 10);
+        Date dateToConvert = calendar.getTime();
+
+        // when
+        LocalDate localDate = DateToLocalDateConverter.convertToLocalDateViaInstant(dateToConvert);
+
+        // then
+        assertEquals(2010, localDate.get(ChronoField.YEAR));
+        assertEquals(11, localDate.get(ChronoField.MONTH_OF_YEAR));
+        assertEquals(10, localDate.get(ChronoField.DAY_OF_MONTH));
+    }
+
+    @Test
+    public void shouldReturn10thNovember2010WhenConvertViaMiliseconds() {
+        // given
+        Calendar calendar = Calendar.getInstance();
+        calendar.set(2010, 10, 10);
+        Date dateToConvert = calendar.getTime();
+
+        // when
+        LocalDate localDate = DateToLocalDateConverter.convertToLocalDateViaMilisecond(dateToConvert);
+
+        // then
+        assertEquals(2010, localDate.get(ChronoField.YEAR));
+        assertEquals(11, localDate.get(ChronoField.MONTH_OF_YEAR));
+        assertEquals(10, localDate.get(ChronoField.DAY_OF_MONTH));
+    }
+
+    @Test
+    public void shouldReturn10thNovember2010WhenConvertViaSqlDate() {
+        // given
+        Calendar calendar = Calendar.getInstance();
+        calendar.set(2010, 10, 10);
+        Date dateToConvert = calendar.getTime();
+
+        // when
+        LocalDate localDate = DateToLocalDateConverter.convertToLocalDateViaSqlDate(dateToConvert);
+
+        // then
+        assertEquals(2010, localDate.get(ChronoField.YEAR));
+        assertEquals(11, localDate.get(ChronoField.MONTH_OF_YEAR));
+        assertEquals(10, localDate.get(ChronoField.DAY_OF_MONTH));
+    }
+
+}

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

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+/**
+ * 
+ */
+package com.baeldung.datetime;
+
+import static org.junit.Assert.assertEquals;
+
+import java.time.LocalDateTime;
+import java.time.temporal.ChronoField;
+import java.util.Calendar;
+import java.util.Date;
+
+import org.junit.Test;
+
+/**
+ * 
+ * JUnits for {@link DateToLocalDateTimeConverter} class.
+ * 
+ * @author abialas
+ *
+ */
+public class DateToLocalDateTimeConverterTest {
+
+    @Test
+    public void shouldReturn10thNovember2010time8hour20minWhenConvertViaInstant() {
+        // given
+        Calendar calendar = Calendar.getInstance();
+        calendar.set(2010, 10, 10, 8, 20);
+        Date dateToConvert = calendar.getTime();
+
+        // when
+        LocalDateTime localDateTime = DateToLocalDateTimeConverter.convertToLocalDateTimeViaInstant(dateToConvert);
+
+        // then
+        assertEquals(2010, localDateTime.get(ChronoField.YEAR));
+        assertEquals(11, localDateTime.get(ChronoField.MONTH_OF_YEAR));
+        assertEquals(10, localDateTime.get(ChronoField.DAY_OF_MONTH));
+        assertEquals(8, localDateTime.get(ChronoField.HOUR_OF_DAY));
+        assertEquals(20, localDateTime.get(ChronoField.MINUTE_OF_HOUR));
+    }
+
+    @Test
+    public void shouldReturn10thNovember2010time8hour20minWhenConvertViaMiliseconds() {
+        // given
+        Calendar calendar = Calendar.getInstance();
+        calendar.set(2010, 10, 10, 8, 20);
+        Date dateToConvert = calendar.getTime();
+
+        // when
+        LocalDateTime localDateTime = DateToLocalDateTimeConverter.convertToLocalDateTimeViaMilisecond(dateToConvert);
+
+        // then
+        assertEquals(2010, localDateTime.get(ChronoField.YEAR));
+        assertEquals(11, localDateTime.get(ChronoField.MONTH_OF_YEAR));
+        assertEquals(10, localDateTime.get(ChronoField.DAY_OF_MONTH));
+        assertEquals(8, localDateTime.get(ChronoField.HOUR_OF_DAY));
+        assertEquals(20, localDateTime.get(ChronoField.MINUTE_OF_HOUR));
+    }
+
+    @Test
+    public void shouldReturn10thNovember2010time8hour20minWhenConvertViaSqlTimestamp() {
+        // given
+        Calendar calendar = Calendar.getInstance();
+        calendar.set(2010, 10, 10, 8, 20);
+        Date dateToConvert = calendar.getTime();
+
+        // when
+        LocalDateTime localDateTime = DateToLocalDateTimeConverter.convertToLocalDateTimeViaSqlTimestamp(dateToConvert);
+
+        // then
+        assertEquals(2010, localDateTime.get(ChronoField.YEAR));
+        assertEquals(11, localDateTime.get(ChronoField.MONTH_OF_YEAR));
+        assertEquals(10, localDateTime.get(ChronoField.DAY_OF_MONTH));
+        assertEquals(8, localDateTime.get(ChronoField.HOUR_OF_DAY));
+        assertEquals(20, localDateTime.get(ChronoField.MINUTE_OF_HOUR));
+    }
+
+}

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

@@ -0,0 +1,61 @@
+/**
+ * 
+ */
+package com.baeldung.datetime;
+
+import static org.junit.Assert.assertEquals;
+
+import java.time.LocalDateTime;
+import java.util.Calendar;
+import java.util.Date;
+
+import org.junit.Test;
+
+/**
+ * 
+ * JUnits for {@link LocalDateTimeToDateConverter} class.
+ * 
+ * @author abialas
+ *
+ */
+public class LocalDateTimeToDateConverterTest {
+
+    @Test
+    public void shouldReturn10thNovember2010time8hour20minWhenConvertViaInstant() {
+        // given
+        LocalDateTime dateToConvert = LocalDateTime.of(2010, 11, 10, 8, 20);
+
+        // when
+        Date date = LocalDateTimeToDateConverter.convertToDateViaInstant(dateToConvert);
+        Calendar calendar = Calendar.getInstance();
+        calendar.setTime(date);
+
+        // then
+        assertEquals(2010, calendar.get(Calendar.YEAR));
+        assertEquals(10, calendar.get(Calendar.MONTH));
+        assertEquals(10, calendar.get(Calendar.DAY_OF_MONTH));
+        assertEquals(8, calendar.get(Calendar.HOUR));
+        assertEquals(20, calendar.get(Calendar.MINUTE));
+        assertEquals(0, calendar.get(Calendar.SECOND));
+    }
+
+    @Test
+    public void shouldReturn10thNovember2010WhenConvertViaSqlTimestamp() {
+        // given
+        LocalDateTime dateToConvert = LocalDateTime.of(2010, 11, 10, 8, 20);
+
+        // when
+        Date date = LocalDateTimeToDateConverter.convertToDateViaSqlTimestamp(dateToConvert);
+        Calendar calendar = Calendar.getInstance();
+        calendar.setTime(date);
+
+        // then
+        assertEquals(2010, calendar.get(Calendar.YEAR));
+        assertEquals(10, calendar.get(Calendar.MONTH));
+        assertEquals(10, calendar.get(Calendar.DAY_OF_MONTH));
+        assertEquals(8, calendar.get(Calendar.HOUR));
+        assertEquals(20, calendar.get(Calendar.MINUTE));
+        assertEquals(0, calendar.get(Calendar.SECOND));
+    }
+
+}

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

@@ -0,0 +1,55 @@
+/**
+ * 
+ */
+package com.baeldung.datetime;
+
+import static org.junit.Assert.assertEquals;
+
+import java.time.LocalDate;
+import java.util.Calendar;
+import java.util.Date;
+
+import org.junit.Test;
+
+/**
+ * 
+ * JUnits for {@link LocalDateToDateConverter} class.
+ * 
+ * @author abialas
+ *
+ */
+public class LocalDateToDateConverterTest {
+
+    @Test
+    public void shouldReturn10thNovember2010WhenConvertViaInstant() {
+        // given
+        LocalDate dateToConvert = LocalDate.of(2010, 11, 10);
+
+        // when
+        Date date = LocalDateToDateConverter.convertToDateViaInstant(dateToConvert);
+        Calendar calendar = Calendar.getInstance();
+        calendar.setTime(date);
+
+        // then
+        assertEquals(2010, calendar.get(Calendar.YEAR));
+        assertEquals(10, calendar.get(Calendar.MONTH));
+        assertEquals(10, calendar.get(Calendar.DAY_OF_MONTH));
+    }
+
+    @Test
+    public void shouldReturn10thNovember2010WhenConvertViaSqlDate() {
+        // given
+        LocalDate dateToConvert = LocalDate.of(2010, 11, 10);
+
+        // when
+        Date date = LocalDateToDateConverter.convertToDateViaSqlDate(dateToConvert);
+        Calendar calendar = Calendar.getInstance();
+        calendar.setTime(date);
+
+        // then
+        assertEquals(2010, calendar.get(Calendar.YEAR));
+        assertEquals(10, calendar.get(Calendar.MONTH));
+        assertEquals(10, calendar.get(Calendar.DAY_OF_MONTH));
+    }
+
+}

core-java-9/src/main/java/com/baeldung/java9/datetime/DateToLocalDateConverter.java

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+/**
+ * 
+ */
+package com.baeldung.java9.datetime;
+
+import java.time.LocalDate;
+import java.time.ZoneId;
+import java.util.Date;
+
+/**
+ * Class which shows a way to convert java.util.Date into java.time.LocalDate with new Java 1.9.
+ * 
+ * @author abialas
+ *
+ */
+public class DateToLocalDateConverter {
+
+    public static LocalDate convertToLocalDate(Date dateToConvert) {
+        return LocalDate.ofInstant(dateToConvert.toInstant(), ZoneId.systemDefault());
+    }
+
+}

core-java-9/src/main/java/com/baeldung/java9/datetime/DateToLocalDateTimeConverter.java

@@ -0,0 +1,22 @@
+/**
+ * 
+ */
+package com.baeldung.java9.datetime;
+
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.util.Date;
+
+/**
+ * Class which shows a way to convert java.util.Date into java.time.LocalDateTime with new Java 1.9.
+ * 
+ * @author abialas
+ *
+ */
+public class DateToLocalDateTimeConverter {
+
+    public static LocalDateTime convertToLocalDateTime(Date dateToConvert) {
+        return LocalDateTime.ofInstant(dateToConvert.toInstant(), ZoneId.systemDefault());
+    }
+
+}

core-java-9/src/test/java/com/baeldung/java9/datetime/DateToLocalDateConverterTest.java

@@ -0,0 +1,41 @@
+/**
+ * 
+ */
+package com.baeldung.java9.datetime;
+
+import static org.junit.Assert.assertEquals;
+
+import java.time.LocalDate;
+import java.time.temporal.ChronoField;
+import java.util.Calendar;
+import java.util.Date;
+
+import org.junit.Test;
+
+import com.baeldung.java9.datetime.DateToLocalDateConverter;
+
+/**
+ * JUnits for {@link DateToLocalDateConverter} class.
+ * 
+ * @author abialas
+ *
+ */
+public class DateToLocalDateConverterTest {
+
+    @Test
+    public void shouldReturn10thNovember2010WhenConvertToLocalDate() {
+        // given
+        Calendar calendar = Calendar.getInstance();
+        calendar.set(2010, 10, 10);
+        Date dateToConvert = calendar.getTime();
+
+        // when
+        LocalDate localDateTime = DateToLocalDateConverter.convertToLocalDate(dateToConvert);
+
+        // then
+        assertEquals(2010, localDateTime.get(ChronoField.YEAR));
+        assertEquals(11, localDateTime.get(ChronoField.MONTH_OF_YEAR));
+        assertEquals(10, localDateTime.get(ChronoField.DAY_OF_MONTH));
+    }
+
+}

core-java-9/src/test/java/com/baeldung/java9/datetime/DateToLocalDateTimeConverterTest.java

@@ -0,0 +1,43 @@
+/**
+ * 
+ */
+package com.baeldung.java9.datetime;
+
+import static org.junit.Assert.assertEquals;
+
+import java.time.LocalDateTime;
+import java.time.temporal.ChronoField;
+import java.util.Calendar;
+import java.util.Date;
+
+import org.junit.Test;
+
+import com.baeldung.java9.datetime.DateToLocalDateTimeConverter;
+
+/**
+ * JUnits for {@link DateToLocalDateTimeConverter} class.
+ * 
+ * @author abialas
+ *
+ */
+public class DateToLocalDateTimeConverterTest {
+
+    @Test
+    public void shouldReturn10thNovember2010time8hour20minWhenConvertViaInstant() {
+        // given
+        Calendar calendar = Calendar.getInstance();
+        calendar.set(2010, 10, 10, 8, 20);
+        Date dateToConvert = calendar.getTime();
+
+        // when
+        LocalDateTime localDateTime = DateToLocalDateTimeConverter.convertToLocalDateTime(dateToConvert);
+
+        // then
+        assertEquals(2010, localDateTime.get(ChronoField.YEAR));
+        assertEquals(11, localDateTime.get(ChronoField.MONTH_OF_YEAR));
+        assertEquals(10, localDateTime.get(ChronoField.DAY_OF_MONTH));
+        assertEquals(8, localDateTime.get(ChronoField.HOUR_OF_DAY));
+        assertEquals(20, localDateTime.get(ChronoField.MINUTE_OF_HOUR));
+    }
+
+}