Merge branch 'master' into PR-7319

core-java-modules/core-java-21/src/main/java/com/baeldung/jfrview/JFRExample.java

@@ -0,0 +1,21 @@
+package com.baeldung.jfrview;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class JFRExample {
+    public static void main(String[] args) {
+        JFRExample se = new JFRExample();
+        se.insertToList(new ArrayList<>());
+    }
+
+    private void insertToList(List<Object> list) {
+        try {
+            while (true) {
+                list.add(new Object());
+            }
+        } catch (OutOfMemoryError e) {
+            System.out.println("Out of Memory. Exiting");
+        }
+    }
+}

core-java-modules/core-java-8-datetime-2/README.md

@@ -9,4 +9,5 @@
 - [Round the Date in Java](https://www.baeldung.com/java-round-the-date)
 - [Representing Furthest Possible Date in Java](https://www.baeldung.com/java-date-represent-max)
 - [Retrieving Unix Time in Java](https://www.baeldung.com/java-retrieve-unix-time)
+- [Calculate Months Between Two Dates in Java](https://www.baeldung.com/java-months-difference-two-dates)
 - [[<-- Prev]](/core-java-modules/core-java-datetime-java8-1)

core-java-modules/core-java-8-datetime-2/src/main/java/com/baeldung/daterangeoverlap/DateRangeOverlapChecker.java

@@ -0,0 +1,46 @@
+package com.baeldung.daterangeoverlap;
+
+import java.time.LocalDate;
+import java.util.Calendar;
+
+import org.joda.time.DateTime;
+import org.joda.time.Interval;
+
+public class DateRangeOverlapChecker {
+
+    public static boolean isOverlapUsingCalendarAndDuration(Calendar start1, Calendar end1, Calendar start2, Calendar end2) {
+        long overlap = Math.min(end1.getTimeInMillis(), end2.getTimeInMillis()) - Math.max(start1.getTimeInMillis(), start2.getTimeInMillis());
+        return overlap >= 0;
+    }
+
+    public static boolean isOverlapUsingLocalDateAndDuration(LocalDate start1, LocalDate end1, LocalDate start2, LocalDate end2) {
+        long overlap = Math.min(end1.toEpochDay(), end2.toEpochDay()) - Math.max(start1.toEpochDay(), start2.toEpochDay());
+        return overlap >= 0;
+    }
+
+    public static boolean isOverlapUsingJodaTime(DateTime start1, DateTime end1, DateTime start2, DateTime end2) {
+        Interval interval1 = new Interval(start1, end1);
+        Interval interval2 = new Interval(start2, end2);
+        return interval1.overlaps(interval2);
+    }
+
+    public static boolean isOverlapUsingCalendarAndCondition(Calendar start1, Calendar end1, Calendar start2, Calendar end2) {
+        return !(end1.before(start2) || start1.after(end2));
+    }
+
+    public static boolean isOverlapUsingLocalDateAndCondition(LocalDate start1, LocalDate end1, LocalDate start2, LocalDate end2) {
+        return !(end1.isBefore(start2) || start1.isAfter(end2));
+    }
+
+    public static boolean isOverlapUsingCalendarAndFindMin(Calendar start1, Calendar end1, Calendar start2, Calendar end2) {
+        long overlap1 = Math.min(end1.getTimeInMillis() - start1.getTimeInMillis(), end1.getTimeInMillis() - start2.getTimeInMillis());
+        long overlap2 = Math.min(end2.getTimeInMillis() - start2.getTimeInMillis(), end2.getTimeInMillis() - start1.getTimeInMillis());
+        return Math.min(overlap1, overlap2) / (24 * 60 * 60 * 1000) >= 0;
+    }
+
+    public static boolean isOverlapUsingLocalDateAndFindMin(LocalDate start1, LocalDate end1, LocalDate start2, LocalDate end2) {
+        long overlap1 = Math.min(end1.toEpochDay() - start1.toEpochDay(), end1.toEpochDay() - start2.toEpochDay());
+        long overlap2 = Math.min(end2.toEpochDay() - start2.toEpochDay(), end2.toEpochDay() - start1.toEpochDay());
+        return Math.min(overlap1, overlap2) >= 0;
+    }
+}

core-java-modules/core-java-8-datetime-2/src/test/java/com/baeldung/daterangeoverlap/DateRangeOverlapCheckerUnitTest.java

@@ -0,0 +1,158 @@
+package com.baeldung.daterangeoverlap;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.time.LocalDate;
+import java.util.Calendar;
+
+import org.joda.time.DateTime;
+import org.junit.Test;
+
+public class DateRangeOverlapCheckerUnitTest {
+
+    @Test
+    public void givenPartialOverlappingRanges_thenReturnsTrue() {
+        Calendar start1 = Calendar.getInstance();
+        start1.set(2024, 11, 15);
+        Calendar end1 = Calendar.getInstance();
+        end1.set(2024, 11, 20);
+
+        Calendar start2 = Calendar.getInstance();
+        start2.set(2024, 11, 18);
+        Calendar end2 = Calendar.getInstance();
+        end2.set(2024, 11, 22);
+
+        LocalDate startLD1 = LocalDate.of(2024, 12, 15);
+        LocalDate endLD1 = LocalDate.of(2024, 12, 20);
+
+        LocalDate startLD2 = LocalDate.of(2024, 12, 18);
+        LocalDate endLD2 = LocalDate.of(2024, 12, 22);
+
+        DateTime startJT1 = new DateTime(2024, 12, 15, 0, 0);
+        DateTime endJT1 = new DateTime(2024, 12, 20, 0, 0);
+
+        DateTime startJT2 = new DateTime(2024, 12, 18, 0, 0);
+        DateTime endJT2 = new DateTime(2024, 12, 22, 0, 0);
+
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingCalendarAndDuration(start1, end1, start2, end2));
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingLocalDateAndDuration(startLD1, endLD1, startLD2, endLD2));
+
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingCalendarAndCondition(start1, end1, start2, end2));
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingLocalDateAndCondition(startLD1, endLD1, startLD2, endLD2));
+
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingCalendarAndFindMin(start1, end1, start2, end2));
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingLocalDateAndFindMin(startLD1, endLD1, startLD2, endLD2));
+
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingJodaTime(startJT1, endJT1, startJT2, endJT2));
+    }
+
+    @Test
+    public void givenFullOverlappingRanges_thenReturnsTrue() {
+        Calendar start1 = Calendar.getInstance();
+        start1.set(2024, 11, 15);
+        Calendar end1 = Calendar.getInstance();
+        end1.set(2024, 11, 20);
+
+        Calendar start2 = Calendar.getInstance();
+        start2.set(2024, 11, 16);
+        Calendar end2 = Calendar.getInstance();
+        end2.set(2024, 11, 18);
+
+        LocalDate startLD1 = LocalDate.of(2024, 12, 15);
+        LocalDate endLD1 = LocalDate.of(2024, 12, 20);
+
+        LocalDate startLD2 = LocalDate.of(2024, 12, 16);
+        LocalDate endLD2 = LocalDate.of(2024, 12, 18);
+
+        DateTime startJT1 = new DateTime(2024, 12, 15, 0, 0);
+        DateTime endJT1 = new DateTime(2024, 12, 20, 0, 0);
+
+        DateTime startJT2 = new DateTime(2024, 12, 16, 0, 0);
+        DateTime endJT2 = new DateTime(2024, 12, 18, 0, 0);
+
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingCalendarAndDuration(start1, end1, start2, end2));
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingLocalDateAndDuration(startLD1, endLD1, startLD2, endLD2));
+
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingCalendarAndCondition(start1, end1, start2, end2));
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingLocalDateAndCondition(startLD1, endLD1, startLD2, endLD2));
+
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingCalendarAndFindMin(start1, end1, start2, end2));
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingLocalDateAndFindMin(startLD1, endLD1, startLD2, endLD2));
+
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingJodaTime(startJT1, endJT1, startJT2, endJT2));
+    }
+
+    @Test
+    public void givenConsecutiveRanges_thenReturnsFalse() {
+        Calendar start1 = Calendar.getInstance();
+        start1.set(2024, 11, 15);
+        Calendar end1 = Calendar.getInstance();
+        end1.set(2024, 11, 20);
+
+        Calendar start2 = Calendar.getInstance();
+        start2.set(2024, 11, 21);
+        Calendar end2 = Calendar.getInstance();
+        end2.set(2024, 11, 24);
+
+        LocalDate startLD1 = LocalDate.of(2024, 12, 15);
+        LocalDate endLD1 = LocalDate.of(2024, 12, 20);
+
+        LocalDate startLD2 = LocalDate.of(2024, 12, 21);
+        LocalDate endLD2 = LocalDate.of(2024, 12, 24);
+
+        DateTime startJT1 = new DateTime(2024, 12, 15, 0, 0);
+        DateTime endJT1 = new DateTime(2024, 12, 20, 0, 0);
+
+        DateTime startJT2 = new DateTime(2024, 12, 21, 0, 0);
+        DateTime endJT2 = new DateTime(2024, 12, 24, 0, 0);
+
+        assertFalse(DateRangeOverlapChecker.isOverlapUsingCalendarAndDuration(start1, end1, start2, end2));
+        assertFalse(DateRangeOverlapChecker.isOverlapUsingLocalDateAndDuration(startLD1, endLD1, startLD2, endLD2));
+
+        assertFalse(DateRangeOverlapChecker.isOverlapUsingCalendarAndCondition(start1, end1, start2, end2));
+        assertFalse(DateRangeOverlapChecker.isOverlapUsingLocalDateAndCondition(startLD1, endLD1, startLD2, endLD2));
+
+        assertFalse(DateRangeOverlapChecker.isOverlapUsingCalendarAndFindMin(start1, end1, start2, end2));
+        assertFalse(DateRangeOverlapChecker.isOverlapUsingLocalDateAndFindMin(startLD1, endLD1, startLD2, endLD2));
+
+        assertFalse(DateRangeOverlapChecker.isOverlapUsingJodaTime(startJT1, endJT1, startJT2, endJT2));
+    }
+
+    @Test
+    public void givenZeroRangeRanges_thenReturnsTrue() {
+        Calendar start1 = Calendar.getInstance();
+        start1.set(2024, 11, 15);
+        Calendar end1 = Calendar.getInstance();
+        end1.set(2024, 11, 20);
+
+        Calendar start2 = Calendar.getInstance();
+        start2.set(2024, 11, 20);
+        Calendar end2 = Calendar.getInstance();
+        end2.set(2024, 11, 20);
+
+        LocalDate startLD1 = LocalDate.of(2024, 12, 15);
+        LocalDate endLD1 = LocalDate.of(2024, 12, 20);
+
+        LocalDate startLD2 = LocalDate.of(2024, 12, 20);
+        LocalDate endLD2 = LocalDate.of(2024, 12, 20);
+
+        DateTime startJT1 = new DateTime(2024, 12, 15, 0, 0);
+        DateTime endJT1 = new DateTime(2024, 12, 20, 0, 0);
+
+        DateTime startJT2 = new DateTime(2024, 12, 20, 0, 0);
+        DateTime endJT2 = new DateTime(2024, 12, 20, 0, 0);
+
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingCalendarAndDuration(start1, end1, start2, end2));
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingLocalDateAndDuration(startLD1, endLD1, startLD2, endLD2));
+
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingCalendarAndCondition(start1, end1, start2, end2));
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingLocalDateAndCondition(startLD1, endLD1, startLD2, endLD2));
+
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingCalendarAndFindMin(start1, end1, start2, end2));
+        assertTrue(DateRangeOverlapChecker.isOverlapUsingLocalDateAndFindMin(startLD1, endLD1, startLD2, endLD2));
+
+        //the overlaps method considers two intervals as overlapping only if they have a non-zero duration.
+        assertFalse(DateRangeOverlapChecker.isOverlapUsingJodaTime(startJT1, endJT1, startJT2, endJT2));
+    }
+}

core-java-modules/core-java-8-datetime-2/src/test/java/com/baeldung/zoneoffsetandzoneidof/ZoneOffSetAndZoneIdOfUnitTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.zoneoffsetandzoneidof;
+
+import org.junit.jupiter.api.Test;
+
+import java.time.OffsetDateTime;
+import java.time.ZoneId;
+import java.time.ZoneOffset;
+import java.time.ZonedDateTime;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class ZoneOffSetAndZoneIdOfUnitTest {
+
+    @Test
+    public void givenOffsetDateTimeWithUTCZoneOffset_thenOffsetShouldBeUTC() {
+        OffsetDateTime dateTimeWithOffset = OffsetDateTime.now(ZoneOffset.UTC);
+        assertEquals(dateTimeWithOffset.getOffset(), ZoneOffset.UTC);
+    }
+
+    @Test
+    public void givenZonedDateTimeWithUTCZoneId_thenZoneShouldBeUTC() {
+        ZonedDateTime zonedDateTime = ZonedDateTime.now(ZoneId.of("UTC"));
+        assertEquals(zonedDateTime.getZone(), ZoneId.of("UTC"));
+    }
+}

core-java-modules/core-java-arrays-convert/src/test/java/com/baeldung/array/conversions/ByteArrayToPrimitiveByteArrayUnitTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.array.conversions;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.apache.commons.lang3.ArrayUtils;
+import org.junit.jupiter.api.Test;
+
+public class ByteArrayToPrimitiveByteArrayUnitTest {
+    private static final byte[] EXPECTED_ARRAY_VALUES = {65, 66, 67, 68};
+    private static final Byte[] BYTE_ARRAY = {65, 66, 67, 68};
+
+    @Test
+    public void givenByteArray_whenConvertingUsingByteValue_thenGiveExpectedResult() {
+        byte[] newByteArray = new byte[BYTE_ARRAY.length];
+        for (int i = 0; i < BYTE_ARRAY.length; i++) {
+            newByteArray[i] = BYTE_ARRAY[i].byteValue();
+        }
+        assertThat(newByteArray).containsExactly(EXPECTED_ARRAY_VALUES);
+    }
+
+    @Test
+    public void givenByteArray_whenConvertingUsingUnboxing_thenGiveExpectedResult() {
+        byte[] newByteArray = new byte[BYTE_ARRAY.length];
+        for (int i = 0; i < BYTE_ARRAY.length; i++) {
+            newByteArray[i] = BYTE_ARRAY[i];
+        }
+        assertThat(newByteArray).containsExactly(EXPECTED_ARRAY_VALUES);
+    }
+
+    @Test
+    public void givenByteArray_whenConvertingArrayUtils_thenGiveExpectedResult() {
+        byte[] newByteArray = ArrayUtils.toPrimitive(BYTE_ARRAY);
+
+        assertThat(newByteArray).containsExactly(EXPECTED_ARRAY_VALUES);
+    }
+}

core-java-modules/core-java-arrays-convert/src/test/java/com/baeldung/array/conversions/PrimitiveByteArrayToByteArrayUnitTest.java

@@ -0,0 +1,47 @@
+package com.baeldung.array.conversions;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Arrays;
+
+import org.apache.commons.lang3.ArrayUtils;
+import org.junit.jupiter.api.Test;
+
+public class PrimitiveByteArrayToByteArrayUnitTest {
+    private static final byte[] PRIMITIVE_BYTE_ARRAY = {65, 66, 67, 68};
+    private static final Byte[] EXPECTED_ARRAY_VALUES = {65, 66, 67, 68};
+
+    @Test
+    public void givenPrimitiveByteArray_whenConvertingUsingByteValueOf_thenGiveExpectedResult() {
+        Byte[] newByteArray = new Byte[PRIMITIVE_BYTE_ARRAY.length];
+        for (int i = 0; i < PRIMITIVE_BYTE_ARRAY.length; i++) {
+            newByteArray[i] = Byte.valueOf(PRIMITIVE_BYTE_ARRAY[i]);
+        }
+        assertThat(newByteArray).containsExactly(EXPECTED_ARRAY_VALUES);
+    }
+
+    @Test
+    public void givenPrimitiveByteArray_whenConvertingUsingAutoboxing_thenGiveExpectedResult() {
+        Byte[] newByteArray = new Byte[PRIMITIVE_BYTE_ARRAY.length];
+        for (int i = 0; i < PRIMITIVE_BYTE_ARRAY.length; i++) {
+            newByteArray[i] = PRIMITIVE_BYTE_ARRAY[i];
+        }
+        assertThat(newByteArray).containsExactly(EXPECTED_ARRAY_VALUES);
+    }
+
+    @Test
+    public void givenPrimitiveByteArray_whenConvertingUsingAutoboxingAndArraysSetAll_thenGiveExpectedResult() {
+        Byte[] newByteArray = new Byte[PRIMITIVE_BYTE_ARRAY.length];
+        Arrays.setAll(newByteArray, n -> PRIMITIVE_BYTE_ARRAY[n]);
+
+        assertThat(newByteArray)
+            .containsExactly(EXPECTED_ARRAY_VALUES);
+    }
+
+    @Test
+    public void givenPrimitiveByteArray_whenConvertingUsingArrayUtils_thenGiveExpectedResult() {
+        Byte[] newByteArray = ArrayUtils.toObject(PRIMITIVE_BYTE_ARRAY);
+
+        assertThat(newByteArray).containsExactly(EXPECTED_ARRAY_VALUES);
+    }
+}

core-java-modules/core-java-char/src/test/java/com/baeldung/unicodechar/UnicodeCharFromCodePointHexStringUnitTest.java

@@ -0,0 +1,70 @@
+package com.baeldung.unicodechar;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class UnicodeCharFromCodePointHexStringUnitTest {
+    private static final String U_CHECK = "✅"; // U+2705
+    private static final String U_STRONG = "强"; // U+5F3A
+
+
+    @Test
+    void whenEscapeUAndNumberInString_thenGetExpectedUnicodeStr() {
+        String check = "\u2705";
+        assertEquals(U_CHECK, check);
+
+        String strong = "\u5F3A";
+        assertEquals(U_STRONG, strong);
+
+        // "A" U+0041
+        assertEquals("A", "\u0041");
+    }
+
+
+    @Test
+    void whenConcatUAndNumberAsString_thenDoNotGetExpectedUnicodeStr() {
+        String check = "\\u" + "2705";
+        assertEquals("\\u2705", check);
+
+        String strong = "\\u" + "5F3A";
+        assertEquals("\\u5F3A", strong);
+    }
+
+
+    @Test
+    void whenCastHexCodePointToCharAndConvertCharToString_thenGetExpectedUnicodeStr() {
+
+        int codePoint = Integer.parseInt("2705", 16); //Decimal int: 9989
+        char[] checkChar = Character.toChars(codePoint);
+        String check = String.valueOf(checkChar);
+        assertEquals(U_CHECK, check);
+
+        // For Java 11 and later versions
+        // assertEquals(U_CHECK, Character.toString(codePoint));
+
+        codePoint = Integer.parseInt("5F3A", 16); //Decimal int: 24378
+        char[] strongChar = Character.toChars(codePoint);
+        String strong = String.valueOf(strongChar);
+        assertEquals(U_STRONG, strong);
+
+        // For Java 11 and later versions
+        // assertEquals(U_STRONG, Character.toString(codePoint));
+    }
+
+    String stringFromCodePointHex(String codePointHex) {
+        int codePoint = Integer.parseInt(codePointHex, 16);
+
+        // For Java 11 and later versions: return Character.toString(codePoint)
+
+        char[] chars = Character.toChars(codePoint);
+        return String.valueOf(chars);
+    }
+
+    @Test
+    void whenUsingstringFromCodePointHex_thenGetExpectedUnicodeStr() {
+        assertEquals("A", stringFromCodePointHex("0041"));
+        assertEquals(U_CHECK, stringFromCodePointHex("2705"));
+        assertEquals(U_STRONG, stringFromCodePointHex("5F3A"));
+    }
+}

core-java-modules/core-java-collections-5/README.md

@@ -11,4 +11,6 @@
 - [Intro to Vector Class in Java](https://www.baeldung.com/java-vector-guide)
 - [HashSet toArray() Method in Java](https://www.baeldung.com/java-hashset-toarray)
 - [Time Complexity of Java Collections Sort in Java](https://www.baeldung.com/java-time-complexity-collections-sort)
+- [Check if List Contains at Least One Enum](https://www.baeldung.com/java-list-check-enum-presence)
+- [Comparison of for Loops and Iterators](https://www.baeldung.com/java-for-loops-vs-iterators)
 - More articles: [[<-- prev]](/core-java-modules/core-java-collections-4)

core-java-modules/core-java-collections-5/src/main/java/com/baeldung/priorityqueueiterator/Person.java

@@ -0,0 +1,36 @@
+package com.baeldung.priorityqueueiterator;
+
+import java.util.Comparator;
+
+public class Person {
+    String name;
+    int age;
+
+    public Person(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+}
+
+class PersonAgeComparator implements Comparator<Person> {
+    @Override
+    public int compare(Person p1, Person p2) {
+        return p1.age - p2.age; // Ascending order
+    }
+}

core-java-modules/core-java-collections-5/src/main/java/com/baeldung/priorityqueueiterator/PriorityQueueMain.java

@@ -0,0 +1,97 @@
+package com.baeldung.priorityqueueiterator;
+
+import java.util.Iterator;
+import java.util.PriorityQueue;
+
+public class PriorityQueueMain {
+
+    public static void main(String[] args) {
+        showPriorityQueueWithIterator();
+        showCustomOrderingWithIterator();
+        showCustomOrderingWithPoll();
+        useIteratorToCapitalizeNames();
+        showFailFastIteratorBehavior();
+    }
+
+    public static void showPriorityQueueWithIterator() {
+        PriorityQueue<Integer> queue = new PriorityQueue<>();
+        queue.add(3);
+        queue.add(1);
+        queue.add(2);
+
+        Iterator<Integer> iterator = queue.iterator();
+
+        while (iterator.hasNext()) {
+            Integer element = iterator.next();
+            System.out.println(element);
+        }
+    }
+
+    public static void showFailFastIteratorBehavior() {
+        PriorityQueue<Integer> numbers = new PriorityQueue<>();
+        numbers.add(3);
+        numbers.add(1);
+        numbers.add(2);
+
+        Iterator<Integer> iterator = numbers.iterator();
+        numbers.add(4);
+
+        try {
+            while (iterator.hasNext()) {
+                System.out.println(iterator.next());
+            }
+        } catch (java.util.ConcurrentModificationException e) {
+            System.out.println("ConcurrentModificationException occurred during iteration.");
+        }
+    }
+
+    public static void showCustomOrderingWithIterator() {
+        // Creating a PriorityQueue with a custom comparator
+        PriorityQueue<Person> priorityQueue = new PriorityQueue<>(new PersonAgeComparator());
+
+        // Adding persons to the PriorityQueue
+        priorityQueue.add(new Person("Alice", 25));
+        priorityQueue.add(new Person("Bob", 30));
+        priorityQueue.add(new Person("Charlie", 22));
+
+        Iterator<Person> iterator = priorityQueue.iterator();
+
+        while (iterator.hasNext()) {
+            Person person = iterator.next();
+            System.out.println("Name: " + person.name + ", Age: " + person.age);
+        }
+    }
+
+    public static void showCustomOrderingWithPoll() {
+        PriorityQueue<Person> priorityQueue = new PriorityQueue<>(new PersonAgeComparator());
+
+        priorityQueue.add(new Person("Alice", 25));
+        priorityQueue.add(new Person("Bob", 30));
+        priorityQueue.add(new Person("Charlie", 22));
+
+        Iterator<Person> iterator = priorityQueue.iterator();
+
+        while (!priorityQueue.isEmpty()) {
+            Person person = priorityQueue.poll();
+            System.out.println("Name: " + person.name + ", Age: " + person.age);
+        }
+    }
+
+    public static void useIteratorToCapitalizeNames() {
+        PriorityQueue<Person> priorityQueue = new PriorityQueue<>(new PersonAgeComparator());
+
+        priorityQueue.add(new Person("Alice", 25));
+        priorityQueue.add(new Person("Bob", 30));
+        priorityQueue.add(new Person("Charlie", 22));
+
+        Iterator<Person> iterator = priorityQueue.iterator();
+
+        while (iterator.hasNext()) {
+            Person person = iterator.next();
+            person.setName(person.getName()
+                .toUpperCase());
+            System.out.println("Name: " + person.name + ", Age: " + person.age);
+        }
+    }
+
+}

core-java-modules/core-java-collections-list-6/README.md

@@ -1,2 +1,5 @@
 ## Relevant Articles
 - [Check if a List Contains a String Element While Ignoring Case](https://www.baeldung.com/java-list-search-case-insensitive)
+- [Removing the Last Node in a Linked List](https://www.baeldung.com/java-linked-list-remove-last-element)
+- [Call a Method on Each Element of a List in Java](https://www.baeldung.com/java-call-method-each-list-item)
+- [Sorting One List Based on Another List in Java](https://www.baeldung.com/java-sorting-one-list-using-another)

core-java-modules/core-java-collections-list-6/src/test/java/com/baeldung/resetlistiterator/ResetListIteratorUnitTest.java

@@ -0,0 +1,46 @@
+package com.baeldung.resetlistiterator;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+import java.util.ListIterator;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+public class ResetListIteratorUnitTest {
+
+    private static final List<String> MY_LIST = List.of("A", "B", "C", "D", "E", "F", "G");
+
+    @Test
+    void whenRecreateAnListIterator_thenGetTheExpectedResult() {
+        ListIterator<String> lit = MY_LIST.listIterator();
+        lit.next();
+        lit.next();
+        lit.next();
+        lit.next();
+
+        lit = MY_LIST.listIterator();
+
+        assertFalse(lit.hasPrevious());
+        assertEquals("A", lit.next());
+    }
+
+    @Test
+    void whenBackwardIterationToTheFirst_thenGetTheExpectedResult() {
+        ListIterator<String> lit = MY_LIST.listIterator();
+        lit.next();
+        lit.next();
+        lit.next();
+        lit.next();
+
+
+        while (lit.hasPrevious()) {
+            lit.previous();
+        }
+
+        assertFalse(lit.hasPrevious());
+        assertEquals("A", lit.next());
+    }
+
+}

core-java-modules/core-java-concurrency-basic-2/README.md

@@ -12,4 +12,5 @@ This module contains articles about basic Java concurrency
 - [How to Get the Number of Threads in a Java Process](https://www.baeldung.com/java-get-number-of-threads)
 - [Set the Name of a Thread in Java](https://www.baeldung.com/java-set-thread-name)
 - [Thread vs. Single Thread Executor Service](https://www.baeldung.com/java-single-thread-executor-service)
+- [Difference Between a Future and a Promise in Java](https://www.baeldung.com/java-future-vs-promise-comparison)
 - [[<-- Prev]](../core-java-concurrency-basic)[[Next -->]](../core-java-concurrency-basic-3)

core-java-modules/core-java-concurrency-basic-3/README.md

@@ -13,4 +13,5 @@ This module contains articles about basic Java concurrency.
 - [Retry Logic with CompletableFuture](https://www.baeldung.com/java-completablefuture-retry-logic)
 - [Convert From List of CompletableFuture to CompletableFuture List](https://www.baeldung.com/java-completablefuture-list-convert)
 - [Synchronize a Static Variable Among Different Threads](https://www.baeldung.com/java-synchronize-static-variable-different-threads)
+- [Difference Between execute() and submit() in Executor Service](https://www.baeldung.com/java-execute-vs-submit-executor-service)
 - [[<-- Prev]](../core-java-concurrency-basic-2)

core-java-modules/core-java-concurrency-basic-3/src/main/java/com/baeldung/concurrent/synchronizestatic/none/Employee.java

@@ -18,7 +18,8 @@ public class Employee {
     }
 
     private static void incrementCount() {
-        System.out.println("Count = " + ++count);
+        ++count;
+        // System.out.println("Count = " + ++count);
     }
 
     public static Integer getCount() {

core-java-modules/core-java-concurrency-basic-3/src/main/java/com/baeldung/concurrent/synchronizestatic/reentrantlock/Employee.java

@@ -24,7 +24,8 @@ public class Employee {
     private static void incrementCount() {
         lock.lock();
         try {
-            System.out.println("Count = " + ++count);
+            ++count;
+            // System.out.println("Count = " + ++count);
         }
         finally {
             lock.unlock();

core-java-modules/core-java-concurrency-basic-3/src/main/java/com/baeldung/concurrent/synchronizestatic/synchronizedblock/Employee.java

@@ -21,7 +21,8 @@ public class Employee {
 
     private static void incrementCount() {
         synchronized(lock) {
-            System.out.println("Count = " + ++count);
+            ++count;
+            // System.out.println("Count = " + ++count);
         }
     }
 

core-java-modules/core-java-concurrency-basic-3/src/main/java/com/baeldung/concurrent/synchronizestatic/synchronizedclass/Employee.java

@@ -19,7 +19,8 @@ public class Employee
 
     private static void incrementCount() {
         synchronized(Employee.class) {
-            System.out.println("Count = " + ++count);
+            ++count;
+            // System.out.println("Count = " + ++count);
         }
     }
 

core-java-modules/core-java-concurrency-basic-3/src/main/java/com/baeldung/concurrent/synchronizestatic/synchronizedmethod/Employee.java

@@ -18,7 +18,8 @@ public class Employee {
     }
 
     private static synchronized void incrementCount() {
-        System.out.println("Count = " + ++count);
+        ++count;
+        // System.out.println("Count = " + ++count);
     }
 
     public static synchronized int getCount() {

core-java-modules/core-java-console/src/main/java/com/baeldung/printmessagewithoutmain/PrintMessageWithoutMainMethod.java

@@ -0,0 +1,33 @@
+package com.baeldung.printmessagewithoutmain;
+
+public final class PrintMessageWithoutMainMethod {
+
+    //Using Static Blocks
+    static {
+        System.out.println("Hello World!!");
+        System.exit(0);
+    }
+
+    //Using Nested Classes
+    static {
+        NestedClass.printMessage();
+    }
+
+    //Executing Code During Class Initialization
+    private static final int STATUS = getStatus();
+    private static int getStatus() {
+        System.out.println("Hello World!!");
+        System.exit(0);
+        return 0;
+    }
+
+    public static void main(String[] args) {
+
+    }
+
+    static class NestedClass {
+        static void printMessage() {
+            System.out.println("Message from nested class");
+        }
+    }
+}

core-java-modules/core-java-console/src/test/java/com/baeldung/printmessagewithoutmain/PrintMessageWithoutMainUnitTest.java

@@ -0,0 +1,10 @@
+package com.baeldung.printmessagewithoutmain;
+
+import org.junit.jupiter.api.Test;
+
+public class PrintMessageWithoutMainUnitTest {
+    @Test
+    public void givenMessage_whenUsingJunitTest_thenPrintMessage() {
+        System.out.println("Hello World!!");
+    }
+}

core-java-modules/core-java-date-operations-4/README.md

@@ -0,0 +1,5 @@
+## Core Date Operations (Part 4)
+This module contains articles about date operations in Java.
+
+### Relevant Articles:
+

core-java-modules/core-java-date-operations-4/pom.xml

@@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-date-operations-4</artifactId>
+    <name>core-java-date-operations-4</name>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>11</source>
+                    <target>11</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>joda-time</groupId>
+            <artifactId>joda-time</artifactId>
+            <version>${joda-time.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <joda-time.version>2.12.6</joda-time.version>
+    </properties>
+
+</project>

core-java-modules/core-java-date-operations-4/src/main/java/com/baeldung/calculateweekdays/CalculateWeekdays.java

@@ -0,0 +1,46 @@
+package com.baeldung.calculateweekdays;
+
+import java.time.DayOfWeek;
+import java.time.LocalDate;
+import java.time.temporal.ChronoUnit;
+import java.time.temporal.TemporalAdjusters;
+import java.util.Arrays;
+
+public class CalculateWeekdays {
+
+    public long getWorkingDaysWithStream(LocalDate start, LocalDate end){
+        return start.datesUntil(end)
+          .map(LocalDate::getDayOfWeek)
+          .filter(day -> !Arrays.asList(DayOfWeek.SATURDAY, DayOfWeek.SUNDAY).contains(day))
+          .count();
+    }
+
+    public long getWorkingDaysWithoutStream(LocalDate start, LocalDate end) {
+        boolean startOnWeekend = false;
+
+        // If starting at the weekend, move to following Monday
+        if(start.getDayOfWeek().getValue() > 5){
+            start = start.with(TemporalAdjusters.next(DayOfWeek.MONDAY));
+            startOnWeekend = true;
+        }
+        boolean endOnWeekend = false;
+        // If ending at the weekend, move to previous Friday
+        if(end.getDayOfWeek().getValue() > 5){
+            end = end.with(TemporalAdjusters.previous(DayOfWeek.FRIDAY));
+            endOnWeekend = true;
+        }
+        // Cover case where starting on Saturday and ending following Sunday
+        if(start.isAfter(end)){
+            return 0;
+        }
+        // Get total weeks
+        long weeks = ChronoUnit.WEEKS.between(start, end);
+
+        long addValue = startOnWeekend || endOnWeekend ? 1 : 0;
+
+        // Add on days that did not make up a full week
+        return ( weeks * 5 ) + ( end.getDayOfWeek().getValue() - start.getDayOfWeek().getValue() ) + addValue;
+    }
+
+
+}

core-java-modules/core-java-date-operations-4/src/test/java/com/baeldung/calculateweekdays/CalculateWeekdaysUnitTest.java

@@ -0,0 +1,83 @@
+package com.baeldung.calculateweekdays;
+
+import static junit.framework.TestCase.assertEquals;
+
+import java.time.LocalDate;
+
+import org.junit.jupiter.api.Test;
+
+public class CalculateWeekdaysUnitTest {
+
+    // Start Saturday end following Sunday (answer is 0)
+    LocalDate startTomorrow = LocalDate.of(2023, 12, 2);
+    LocalDate endTomorrow = LocalDate.of(2023, 12, 3);
+
+    // Three week gap with midweek start and finish (answer is 17)
+    LocalDate startThreeWeeks = LocalDate.of(2023, 11, 28);
+    LocalDate endThreeWeeks = LocalDate.of(2023, 12, 21);
+
+    // Three week gap with midweek start and weekend finish (answer is 17)
+    LocalDate startThreeWeeks2 = LocalDate.of(2023, 11, 6);
+    LocalDate endThreeWeeks2 = LocalDate.of(2023, 12, 30);
+
+    // Week gap start and end on weekend (answer is 40)
+    LocalDate startThreeWeeksWeekend = LocalDate.of(2023, 12, 2);
+    LocalDate endThreeWeeksWeekend = LocalDate.of(2023, 12, 9);
+
+    @Test
+    void givenTwoDaysOnSameWeekend_whenUsingStreams_thenCalculateWeekdays(){
+        CalculateWeekdays c = new CalculateWeekdays();
+        long result = c.getWorkingDaysWithStream(startTomorrow, endTomorrow);
+        assertEquals(0, result);
+    }
+
+    @Test
+    void givenTwoDaysOnSameWeekend_whenUsingMaths_thenCalculateWeekdays(){
+        CalculateWeekdays c = new CalculateWeekdays();
+        long result = c.getWorkingDaysWithoutStream(startTomorrow, endTomorrow);
+        assertEquals(0, result);
+    }
+
+    @Test
+    void givenAThreeWeekGapMidweekDates_whenUsingStreams_thenCalculateWeekdays(){
+        CalculateWeekdays c = new CalculateWeekdays();
+        long result = c.getWorkingDaysWithStream(startThreeWeeks, endThreeWeeks);
+        assertEquals(17, result);
+    }
+
+    @Test
+    void givenAThreeWeekGapMidweekDates_whenUsingMaths_thenCalculateWeekdays(){
+        CalculateWeekdays c = new CalculateWeekdays();
+        long result = c.getWorkingDaysWithoutStream(startThreeWeeks, endThreeWeeks);
+        assertEquals(17, result);
+    }
+
+    @Test
+    void givenThreeWeekGapMidweekAndWeekendDates_whenUsingStreams_thenCalculateWeekdays(){
+        CalculateWeekdays c = new CalculateWeekdays();
+        long result = c.getWorkingDaysWithStream(startThreeWeeksWeekend, endThreeWeeksWeekend);
+        assertEquals(5, result);
+    }
+
+    @Test
+    void givenThreeWeekGapMidweekAndWeekendDates_whenUsingMaths_thenCalculateWeekdays(){
+        CalculateWeekdays c = new CalculateWeekdays();
+        long result = c.getWorkingDaysWithoutStream(startThreeWeeksWeekend, endThreeWeeksWeekend);
+        assertEquals(5, result);
+    }
+
+    @Test
+    void givenThreeWeekGapWeekendDates_whenUsingStreams_thenCalculateWeekdays(){
+        CalculateWeekdays c = new CalculateWeekdays();
+        long result = c.getWorkingDaysWithStream(startThreeWeeks2, endThreeWeeks2);
+        assertEquals(40, result);
+    }
+
+    @Test
+    void givenThreeWeekGapWeekendDates_whenUsingMaths_thenCalculateWeekdays(){
+        CalculateWeekdays c = new CalculateWeekdays();
+        long result = c.getWorkingDaysWithoutStream(startThreeWeeks2, endThreeWeeks2);
+        assertEquals(40, result);
+    }
+
+}

core-java-modules/core-java-date-operations-4/src/test/java/com/baeldung/longtodate/LongToDateUnitTest.java

@@ -0,0 +1,74 @@
+package com.baeldung.longtodate;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.time.LocalDate;
+import java.util.Calendar;
+import java.util.Date;
+import java.util.TimeZone;
+
+import org.joda.time.DateTimeZone;
+import org.joda.time.Instant;
+import org.junit.jupiter.api.Test;
+
+class LongToDateUnitTest {
+
+    @Test
+    void givenLongValue_whenUsingInstantClass_thenConvert() {
+        Instant expectedDate = Instant.parse("2020-09-08T12:16:40Z");
+        long seconds = 1599567400L;
+
+        Instant date = Instant.ofEpochSecond(seconds);
+
+        assertEquals(expectedDate, date);
+    }
+
+    @Test
+    void givenLongValue_whenUsingLocalDateClass_thenConvert() {
+        LocalDate expectedDate = LocalDate.of(2023, 10, 17);
+        long epochDay = 19647L;
+
+        LocalDate date = LocalDate.ofEpochDay(epochDay);
+
+        assertEquals(expectedDate, date);
+    }
+
+    @Test
+    void givenLongValue_whenUsingDateClass_thenConvert() throws ParseException {
+        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
+        dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
+        Date expectedDate = dateFormat.parse("2023-07-15 22:00:00");
+        long milliseconds = 1689458400000L;
+
+        Date date = new Date(milliseconds);
+
+        assertEquals(expectedDate, date);
+    }
+
+    @Test
+    void givenLongValue_whenUsingCalendarClass_thenConvert() throws ParseException {
+        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
+        dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
+        Date expectedDate = dateFormat.parse("2023-07-15 22:00:00");
+        long milliseconds = 1689458400000L;
+
+        Calendar calendar = Calendar.getInstance();
+        calendar.setTimeZone(TimeZone.getTimeZone("UTC"));
+        calendar.setTimeInMillis(milliseconds);
+
+        assertEquals(expectedDate, calendar.getTime());
+    }
+
+    @Test
+    void givenLongValue_whenUsingJodaTimeLocalDateClass_thenConvert() {
+        org.joda.time.LocalDate expectedDate = new org.joda.time.LocalDate(2023, 7, 15);
+        long milliseconds = 1689458400000L;
+
+        org.joda.time.LocalDate date = new org.joda.time.LocalDate(milliseconds, DateTimeZone.UTC);
+
+        assertEquals(expectedDate, date);
+    }
+
+}

core-java-modules/core-java-datetime-conversion-2/README.md

@@ -0,0 +1,6 @@
+## Java Date/time conversion Cookbooks and Examples
+
+This module contains articles about converting between Java date and time objects.
+
+### Relevant Articles: 
+

core-java-modules/core-java-datetime-conversion-2/pom.xml

@@ -0,0 +1,57 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-datetime-conversion-2</artifactId>
+    <version>${project.parent.version}</version>
+    <name>core-java-datetime-conversion-2</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>joda-time</groupId>
+            <artifactId>joda-time</artifactId>
+            <version>${joda-time.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <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>
+        <finalName>core-java-datetime-conversion-2</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+    <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-2/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;
+    }
+}