Add code for Gregorian date to a Hijri date conversion (#15696)

Co-authored-by: rajatgarg <rajatgarg@adobe.com>

core-java-modules/core-java-datetime-conversion/pom.xml

@@ -25,6 +25,12 @@
             <artifactId>commons-lang3</artifactId>
             <version>${commons-lang3.version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.github.msarhan</groupId>
+            <artifactId>ummalqura-calendar</artifactId>
+            <version>${ummalqura-calendar.version}</version>
+        </dependency>
+
     </dependencies>
 
     <build>
@@ -45,6 +51,7 @@
 
     <properties>
         <joda-time.version>2.12.5</joda-time.version>
+        <ummalqura-calendar.version>2.0.2</ummalqura-calendar.version>
     </properties>
 
 </project>

core-java-modules/core-java-datetime-conversion/src/main/java/com/baeldung/gregoriantohijri/GregorianToHijriDateConverter.java

@@ -0,0 +1,34 @@
+package com.baeldung.gregoriantohijri;
+
+import java.text.ParseException;
+import java.time.LocalDate;
+import java.time.chrono.ChronoLocalDate;
+import java.time.chrono.HijrahChronology;
+import java.time.chrono.HijrahDate;
+import java.util.GregorianCalendar;
+
+import org.joda.time.chrono.IslamicChronology;
+
+import com.github.msarhan.ummalqura.calendar.UmmalquraCalendar;
+
+public class GregorianToHijriDateConverter {
+    public static HijrahDate usingHijrahChronology(LocalDate gregorianDate) {
+        HijrahChronology hijrahChronology = HijrahChronology.INSTANCE;
+        ChronoLocalDate hijriChronoLocalDate = hijrahChronology.date(gregorianDate);
+        return HijrahDate.from(hijriChronoLocalDate);
+    }
+
+    public static HijrahDate usingFromMethod(LocalDate gregorianDate) {
+        return HijrahDate.from(gregorianDate);
+    }
+
+    public static org.joda.time.DateTime usingJodaDate(org.joda.time.DateTime gregorianDate) {
+        return gregorianDate.withChronology(IslamicChronology.getInstance());
+    }
+
+    public static UmmalquraCalendar usingUmmalquraCalendar(GregorianCalendar gregorianCalendar) throws ParseException {
+        UmmalquraCalendar hijriCalendar = new UmmalquraCalendar();
+        hijriCalendar.setTime(gregorianCalendar.getTime());
+        return hijriCalendar;
+    }
+}

core-java-modules/core-java-datetime-conversion/src/test/java/com/baeldung/gregoriantohijri/GregorianToHijriDateConverterUnitTest.java

@@ -0,0 +1,53 @@
+package com.baeldung.gregoriantohijri;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.text.ParseException;
+import java.time.LocalDate;
+import java.time.chrono.HijrahDate;
+import java.time.temporal.ChronoField;
+import java.util.Calendar;
+import java.util.GregorianCalendar;
+
+import org.joda.time.DateTime;
+import org.junit.jupiter.api.Test;
+
+import com.github.msarhan.ummalqura.calendar.UmmalquraCalendar;
+
+public class GregorianToHijriDateConverterUnitTest {
+        @Test
+        void givenGregorianDate_whenUsingHijrahChronologyClass_thenConvertHijriDate() {
+            LocalDate gregorianDate = LocalDate.of(2013, 3, 31);
+            HijrahDate hijriDate = GregorianToHijriDateConverter.usingHijrahChronology(gregorianDate);
+            assertEquals(1434, hijriDate.get(ChronoField.YEAR));
+            assertEquals(5, hijriDate.get(ChronoField.MONTH_OF_YEAR));
+            assertEquals(19, hijriDate.get(ChronoField.DAY_OF_MONTH));
+        }
+
+    @Test
+    void givenGregorianDate_whenUsingFromMethod_thenConvertHijriDate() {
+        LocalDate gregorianDate = LocalDate.of(2013, 3, 31);
+        HijrahDate hijriDate = GregorianToHijriDateConverter.usingFromMethod(gregorianDate);
+        assertEquals(1434, hijriDate.get(ChronoField.YEAR));
+        assertEquals(5, hijriDate.get(ChronoField.MONTH_OF_YEAR));
+        assertEquals(19, hijriDate.get(ChronoField.DAY_OF_MONTH));
+    }
+
+    @Test
+    void givenGregorianDate_whenUsingJodaDate_thenConvertHijriDate() {
+        DateTime gregorianDate = new DateTime(2013, 3, 31, 0, 0, 0);
+        DateTime hijriDate = GregorianToHijriDateConverter.usingJodaDate(gregorianDate);
+        assertEquals(1434, hijriDate.getYear());
+        assertEquals(5, hijriDate.getMonthOfYear());
+        assertEquals(19, hijriDate.getDayOfMonth());
+    }
+
+    @Test
+    void givenGregorianDate_whenUsingUmmalquraCalendar_thenConvertHijriDate() throws ParseException {
+        GregorianCalendar gregorianCalendar = new GregorianCalendar(2013, Calendar.MARCH, 31);
+        UmmalquraCalendar ummalquraCalendar = GregorianToHijriDateConverter.usingUmmalquraCalendar(gregorianCalendar);
+        assertEquals(1434, ummalquraCalendar.get(Calendar.YEAR));
+        assertEquals(5, ummalquraCalendar.get(Calendar.MONTH) + 1);
+        assertEquals(19, ummalquraCalendar.get(Calendar.DAY_OF_MONTH));
+    }
+}