[BAEL-16640] - Fixed conflicts

algorithms-miscellaneous-4/src/main/java/com/baeldung/algorithms/smallestinteger/SmallestMissingPositiveInteger.java

@@ -0,0 +1,37 @@
+package com.baeldung.algorithms.smallestinteger;
+
+import java.util.Arrays;
+
+public class SmallestMissingPositiveInteger {
+    public static int searchInSortedArray(int[] input) {
+        for (int i = 0; i < input.length; i++) {
+            if (i != input[i]) {
+                return i;
+            }
+        }
+
+        return input.length;
+    }
+
+    public static int searchInUnsortedArraySortingFirst(int[] input) {
+        Arrays.sort(input);
+        return searchInSortedArray(input);
+    }
+
+    public static int searchInUnsortedArrayBooleanArray(int[] input) {
+        boolean[] flags = new boolean[input.length];
+        for (int number : input) {
+            if (number < flags.length) {
+                flags[number] = true;
+            }
+        }
+
+        for (int i = 0; i < flags.length; i++) {
+            if (!flags[i]) {
+                return i;
+            }
+        }
+
+        return flags.length;
+    }
+}

algorithms-miscellaneous-4/src/test/java/com/baeldung/algorithms/smallestinteger/SmallestMissingPositiveIntegerUnitTest.java

@@ -0,0 +1,88 @@
+package com.baeldung.algorithms.smallestinteger;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class SmallestMissingPositiveIntegerUnitTest {
+    @Test
+    void givenArrayWithThreeMissing_whenSearchInSortedArray_thenThree() {
+        int[] input = new int[] {0, 1, 2, 4, 5};
+
+        int result = SmallestMissingPositiveInteger.searchInSortedArray(input);
+
+        assertThat(result).isEqualTo(3);
+    }
+
+    @Test
+    void givenArrayWithOneAndThreeMissing_whenSearchInSortedArray_thenOne() {
+        int[] input = new int[] {0, 2, 4, 5};
+
+        int result = SmallestMissingPositiveInteger.searchInSortedArray(input);
+
+        assertThat(result).isEqualTo(1);
+    }
+
+    @Test
+    void givenArrayWithoutMissingInteger_whenSearchInSortedArray_thenArrayLength() {
+        int[] input = new int[] {0, 1, 2, 3, 4, 5};
+
+        int result = SmallestMissingPositiveInteger.searchInSortedArray(input);
+
+        assertThat(result).isEqualTo(input.length);
+    }
+
+    @Test
+    void givenArrayWithThreeMissing_whenSearchInUnsortedArraySortingFirst_thenThree() {
+        int[] input = new int[] {1, 4, 0, 5, 2};
+
+        int result = SmallestMissingPositiveInteger.searchInUnsortedArraySortingFirst(input);
+
+        assertThat(result).isEqualTo(3);
+    }
+
+    @Test
+    void givenArrayWithOneAndThreeMissing_whenSearchInUnsortedArraySortingFirst_thenOne() {
+        int[] input = new int[] {4, 2, 0, 5};
+
+        int result = SmallestMissingPositiveInteger.searchInUnsortedArraySortingFirst(input);
+
+        assertThat(result).isEqualTo(1);
+    }
+
+    @Test
+    void givenArrayWithoutMissingInteger_whenSearchInUnsortedArraySortingFirst_thenArrayLength() {
+        int[] input = new int[] {4, 5, 1, 3, 0, 2};
+
+        int result = SmallestMissingPositiveInteger.searchInUnsortedArraySortingFirst(input);
+
+        assertThat(result).isEqualTo(input.length);
+    }
+
+    @Test
+    void givenArrayWithThreeMissing_whenSearchInUnsortedArrayBooleanArray_thenThree() {
+        int[] input = new int[] {1, 4, 0, 5, 2};
+
+        int result = SmallestMissingPositiveInteger.searchInUnsortedArrayBooleanArray(input);
+
+        assertThat(result).isEqualTo(3);
+    }
+
+    @Test
+    void givenArrayWithOneAndThreeMissing_whenSearchInUnsortedArrayBooleanArray_thenOne() {
+        int[] input = new int[] {4, 2, 0, 5};
+
+        int result = SmallestMissingPositiveInteger.searchInUnsortedArrayBooleanArray(input);
+
+        assertThat(result).isEqualTo(1);
+    }
+
+    @Test
+    void givenArrayWithoutMissingInteger_whenSearchInUnsortedArrayBooleanArray_thenArrayLength() {
+        int[] input = new int[] {4, 5, 1, 3, 0, 2};
+
+        int result = SmallestMissingPositiveInteger.searchInUnsortedArrayBooleanArray(input);
+
+        assertThat(result).isEqualTo(input.length);
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/balancedbinarytree/BalancedBinaryTree.java

@@ -0,0 +1,33 @@
+package com.baeldung.algorithms.balancedbinarytree;
+
+public class BalancedBinaryTree {
+
+    public static boolean isBalanced(Tree tree) {
+        return isBalancedRecursive(tree, -1).isBalanced;
+    }
+
+    private static Result isBalancedRecursive(Tree tree, int depth) {
+        if (tree == null) {
+            return new Result(true, -1);
+        }
+
+        Result leftSubtreeResult = isBalancedRecursive(tree.left(), depth + 1);
+        Result rightSubtreeResult = isBalancedRecursive(tree.right(), depth + 1);
+
+        boolean isBalanced = Math.abs(leftSubtreeResult.height - rightSubtreeResult.height) <= 1;
+        boolean subtreesAreBalanced = leftSubtreeResult.isBalanced && rightSubtreeResult.isBalanced;
+        int height = Math.max(leftSubtreeResult.height, rightSubtreeResult.height) + 1;
+
+        return new Result(isBalanced && subtreesAreBalanced, height);
+    }
+
+    private static final class Result {
+        private final boolean isBalanced;
+        private final int height;
+
+        private Result(boolean isBalanced, int height) {
+            this.isBalanced = isBalanced;
+            this.height = height;
+        }
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/balancedbinarytree/Tree.java

@@ -0,0 +1,34 @@
+package com.baeldung.algorithms.balancedbinarytree;
+
+public class Tree {
+    private final int value;
+    private final Tree left;
+    private final Tree right;
+
+    public Tree(int value, Tree left, Tree right) {
+        this.value = value;
+        this.left = left;
+        this.right = right;
+    }
+
+    public int value() {
+        return value;
+    }
+
+    public Tree left() {
+        return left;
+    }
+
+    public Tree right() {
+        return right;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("[%s, %s, %s]",
+            value,
+            left == null ? "null" : left.toString(),
+            right == null ? "null" : right.toString()
+        );
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/binarygap/BinaryGap.java

@@ -0,0 +1,17 @@
+package com.baeldung.algorithms.binarygap;
+
+public class BinaryGap {
+    static int calculateBinaryGap(int n) {
+        return calculateBinaryGap(n >>> Integer.numberOfTrailingZeros(n), 0, 0);
+    }
+
+    static int calculateBinaryGap(int n, int current, int maximum) {
+        if (n == 0) {
+            return maximum;
+        } else if ((n & 1) == 0) {
+            return calculateBinaryGap(n >>> 1, current + 1, maximum);
+        } else {
+            return calculateBinaryGap(n >>> 1, 0, Math.max(maximum, current));
+        }
+    }
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/balancedbinarytree/BalancedBinaryTreeUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.algorithms.balancedbinarytree;
+
+import org.junit.Test;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertFalse;
+
+public class BalancedBinaryTreeUnitTest extends BinaryTreeDataProvider {
+
+    @Test
+    public void givenBalancedTrees_whenCallingIsBalanced_ShouldReturnTrue() {
+        for (Tree tree : balancedTrees()) {
+            assertTrue(toString(tree) + " should be balanced", BalancedBinaryTree.isBalanced(tree));
+        }
+    }
+
+    @Test
+    public void givenUnbalancedTrees_whenCallingIsBalanced_ShouldReturnFalse() {
+        for (Tree tree : unbalancedTrees()) {
+            assertFalse(toString(tree) + " should not be balanced", BalancedBinaryTree.isBalanced(tree));
+        }
+    }
+
+    private String toString(Tree tree) {
+        return tree != null ? tree.toString() : "null";
+    }
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/balancedbinarytree/BinaryTreeDataProvider.java

@@ -0,0 +1,69 @@
+package com.baeldung.algorithms.balancedbinarytree;
+
+import java.util.Arrays;
+import java.util.Collection;
+
+class BinaryTreeDataProvider {
+
+    static Collection<Tree> balancedTrees() {
+        return Arrays.asList(
+            null,
+            leaf(1),
+            tree(1, leaf(2), leaf(3)),
+            tree(
+                1,
+                leaf(2),
+                tree(3, leaf(4), null)
+            ),
+            tree(
+                1,
+                tree(
+                    2,
+                    tree(3, leaf(4), null),
+                    leaf(5)
+                ),
+                tree(
+                    6,
+                    leaf(7),
+                    tree(8, null, leaf(9))
+                )
+            )
+        );
+    }
+
+    static Collection<Tree> unbalancedTrees() {
+        return Arrays.asList(
+            tree(
+                1,
+                tree(2, leaf(3), null),
+                null
+            ),
+            tree(
+                1,
+                tree(
+                    2,
+                    tree(3, leaf(4), leaf(5)),
+                    null
+                ),
+                tree(6, leaf(7), null)
+            ),
+            tree(
+                1,
+                tree(2, leaf(3), null),
+                tree(
+                    4,
+                    tree(5, leaf(6), leaf(7)),
+                    null
+                )
+            )
+        );
+    }
+
+    private static Tree leaf(int value) {
+        return new Tree(value, null, null);
+    }
+
+    private static Tree tree(int value, Tree left, Tree right) {
+        return new Tree(value, left, right);
+    }
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/binarygap/BinaryGapUnitTest.java

@@ -0,0 +1,34 @@
+package com.baeldung.algorithms.binarygap;
+
+import static com.baeldung.algorithms.binarygap.BinaryGap.calculateBinaryGap;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class BinaryGapUnitTest {
+
+    @Test public void givenNoOccurrenceOfBoundedZeros_whenCalculateBinaryGap_thenOutputCorrectResult() {
+
+        int result = calculateBinaryGap(63);
+        assertEquals(0, result);
+    }
+
+    @Test public void givenTrailingZeros_whenCalculateBinaryGap_thenOutputCorrectResult() {
+
+        int result = calculateBinaryGap(40);
+        assertEquals(1, result);
+    }
+
+    @Test public void givenSingleOccurrenceOfBoundedZeros_whenCalculateBinaryGap_thenOutputCorrectResult() {
+
+        int result = calculateBinaryGap(9);
+        assertEquals(2, result);
+    }
+
+    @Test public void givenMultipleOccurrenceOfBoundedZeros_whenCalculateBinaryGap_thenOutputCorrectResult() {
+
+        int result = calculateBinaryGap(145);
+        assertEquals(3, result);
+    }
+
+}

core-java-modules/core-java-9-improvements/README.md

@@ -0,0 +1,17 @@
+## Core Java 9
+
+This module contains articles about the improvements to core Java features introduced with Java 9.
+
+### Relevant Articles:
+
+- [New Stream Collectors in Java 9](http://www.baeldung.com/java9-stream-collectors)
+- [Java 9 Optional API Additions](https://www.baeldung.com/java-9-optional)
+- [Java 9 Convenience Factory Methods for Collections](https://www.baeldung.com/java-9-collections-factory-methods)
+- [Java 9 Stream API Improvements](https://www.baeldung.com/java-9-stream-api)
+- [Java 9 java.util.Objects Additions](https://www.baeldung.com/java-9-objects-new)
+- [Java 9 CompletableFuture API Improvements](https://www.baeldung.com/java-9-completablefuture)
+
+#### Relevant articles not in this module:
+
+- [Java 9 Process API Improvements](https://www.baeldung.com/java-9-process-api) (see the [core-java-os](/core-java-os) module)
+

core-java-modules/core-java-9-improvements/pom.xml

@@ -0,0 +1,73 @@
+<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-9</artifactId>
+    <version>0.2-SNAPSHOT</version>
+    <name>core-java-9</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.jayway.awaitility</groupId>
+            <artifactId>awaitility</artifactId>
+            <version>${awaitility.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-runner</artifactId>
+            <version>${junit.platform.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-9</finalName>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <pluginRepositories>
+        <pluginRepository>
+            <id>apache.snapshots</id>
+            <url>http://repository.apache.org/snapshots/</url>
+        </pluginRepository>
+    </pluginRepositories>
+
+    <properties>
+        <!-- testing -->
+        <assertj.version>3.10.0</assertj.version>
+        <junit.platform.version>1.2.0</junit.platform.version>
+        <awaitility.version>1.7.0</awaitility.version>
+        <maven.compiler.source>1.9</maven.compiler.source>
+        <maven.compiler.target>1.9</maven.compiler.target>
+        <guava.version>25.1-jre</guava.version>
+    </properties>
+
+</project>

core-java-modules/core-java-9-jigsaw/README.md

@@ -0,0 +1,11 @@
+## Core Java 9
+
+This module contains articles about Project Jigsaw and the Java Platform Module System (JPMS), introduced with Java 9.
+
+### Relevant Articles:
+
+- [Introduction to Project Jigsaw](http://www.baeldung.com/project-jigsaw-java-modularity)
+- [A Guide to Java 9 Modularity](https://www.baeldung.com/java-9-modularity)
+- [Java 9 java.lang.Module API](https://www.baeldung.com/java-9-module-api)
+
+

core-java-modules/core-java-9-jigsaw/pom.xml

@@ -0,0 +1,35 @@
+<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-9-jigsaw</artifactId>
+    <version>0.2-SNAPSHOT</version>
+    <name>core-java-9</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <build>
+        <finalName>core-java-9-jigsaw</finalName>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <maven.compiler.source>1.9</maven.compiler.source>
+        <maven.compiler.target>1.9</maven.compiler.target>
+    </properties>
+
+</project>

core-java-modules/core-java-9-new-features/README.md

@@ -0,0 +1,14 @@
+## Core Java 9
+
+This module contains articles about core Java features that have been introduced in Java 9.
+
+### Relevant Articles:
+
+- [Java 9 New Features](https://www.baeldung.com/new-java-9)
+- [Java 9 Variable Handles Demystified](http://www.baeldung.com/java-variable-handles)
+- [Exploring the New HTTP Client in Java 9 and 11](http://www.baeldung.com/java-9-http-client)
+- [Multi-Release Jar Files](https://www.baeldung.com/java-multi-release-jar)
+- [Ahead of Time Compilation (AoT)](https://www.baeldung.com/ahead-of-time-compilation)
+- [Introduction to Java 9 StackWalking API](https://www.baeldung.com/java-9-stackwalking-api)
+- [Java 9 Platform Logging API](https://www.baeldung.com/java-9-logging-api)
+- [Java 9 Reactive Streams](https://www.baeldung.com/java-9-reactive-streams)

core-java-modules/core-java-9-new-features/pom.xml

@@ -0,0 +1,60 @@
+<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-9-new-features</artifactId>
+    <version>0.2-SNAPSHOT</version>
+    <name>core-java-9</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-runner</artifactId>
+            <version>${junit.platform.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-9-new-features</finalName>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <pluginRepositories>
+        <pluginRepository>
+            <id>apache.snapshots</id>
+            <url>http://repository.apache.org/snapshots/</url>
+        </pluginRepository>
+    </pluginRepositories>
+
+    <properties>
+        <!-- testing -->
+        <assertj.version>3.10.0</assertj.version>
+        <junit.platform.version>1.2.0</junit.platform.version>
+        <maven.compiler.source>1.9</maven.compiler.source>
+        <maven.compiler.target>1.9</maven.compiler.target>
+    </properties>
+
+</project>

core-java-modules/core-java-9/.gitignore

@@ -1,13 +0,0 @@
-*.class
-
-#folders#
-/target
-/neoDb*
-/data
-/src/main/webapp/WEB-INF/classes
-*/META-INF/*
-
-# Packaged files #
-*.jar
-*.war
-*.ear

core-java-modules/core-java-9/README.md

@@ -4,28 +4,13 @@ This module contains articles about Java 9 core features
 
 ### Relevant Articles:
 
-- [Java 9 New Features](https://www.baeldung.com/new-java-9)
-- [New Stream Collectors in Java 9](http://www.baeldung.com/java9-stream-collectors)
-- [Introduction to Project Jigsaw](http://www.baeldung.com/project-jigsaw-java-modularity)
-- [Java 9 Variable Handles Demystified](http://www.baeldung.com/java-variable-handles)
-- [Exploring the New HTTP Client in Java 9 and 11](http://www.baeldung.com/java-9-http-client)
 - [Method Handles in Java](http://www.baeldung.com/java-method-handles)
 - [Introduction to Chronicle Queue](http://www.baeldung.com/java-chronicle-queue)
 - [Optional orElse Optional](http://www.baeldung.com/java-optional-or-else-optional)
 - [Iterate Through a Range of Dates in Java](https://www.baeldung.com/java-iterate-date-range)
 - [Initialize a HashMap in Java](https://www.baeldung.com/java-initialize-hashmap)
 - [Immutable Set in Java](https://www.baeldung.com/java-immutable-set)
-- [Multi-Release Jar Files](https://www.baeldung.com/java-multi-release-jar)
-- [Ahead of Time Compilation (AoT)](https://www.baeldung.com/ahead-of-time-compilation)
-- [Java 9 Process API Improvements](https://www.baeldung.com/java-9-process-api)
-- [Java 9 java.util.Objects Additions](https://www.baeldung.com/java-9-objects-new)
-- [Java 9 Reactive Streams](https://www.baeldung.com/java-9-reactive-streams)
-- [Java 9 Optional API Additions](https://www.baeldung.com/java-9-optional)
-- [Java 9 CompletableFuture API Improvements](https://www.baeldung.com/java-9-completablefuture)
-- [Introduction to Java 9 StackWalking API](https://www.baeldung.com/java-9-stackwalking-api)
-- [Java 9 Convenience Factory Methods for Collections](https://www.baeldung.com/java-9-collections-factory-methods)
-- [Java 9 Stream API Improvements](https://www.baeldung.com/java-9-stream-api)
-- [A Guide to Java 9 Modularity](https://www.baeldung.com/java-9-modularity)
-- [Java 9 java.lang.Module API](https://www.baeldung.com/java-9-module-api)
-- [Java 9 Platform Logging API](https://www.baeldung.com/java-9-logging-api)
 - [Filtering a Stream of Optionals in Java](https://www.baeldung.com/java-filter-stream-of-optional)
+
+Note: also contains part of the code for the article
+[How to Filter a Collection in Java](https://www.baeldung.com/java-collection-filtering).

core-java-modules/core-java-9/src/main/java/.gitignore

@@ -1,13 +0,0 @@
-*.class
-
-#folders#
-/target
-/neoDb*
-/data
-/src/main/webapp/WEB-INF/classes
-*/META-INF/*
-
-# Packaged files #
-*.jar
-*.war
-*.ear

core-java-modules/core-java-9/src/test/java/com/baeldung/java9/README.MD

@@ -1,2 +0,0 @@
-### Relevant Artiles:
-- [Filtering a Stream of Optionals in Java](http://www.baeldung.com/java-filter-stream-of-optional)

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

@@ -0,0 +1,17 @@
+<?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</artifactId>
+    <version>${project.parent.version}</version>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-java</relativePath>
+    </parent>
+
+</project>

core-java-modules/core-java-date-operations/src/main/java/com/baeldung/datetime/CalendarUtils.java

@@ -0,0 +1,15 @@
+package com.baeldung.datetime;
+
+import java.text.ParseException;
+import java.util.Calendar;
+import java.util.Date;
+
+public class CalendarUtils {
+
+    public static Calendar getPlusDays(Date date, int amount) throws ParseException {
+        Calendar calendar = Calendar.getInstance();
+        calendar.setTime(date);
+        calendar.add(Calendar.DAY_OF_YEAR, amount);
+        return calendar;
+    }
+}

core-java-modules/core-java-date-operations/src/main/java/com/baeldung/datetime/DateUtils.java

@@ -0,0 +1,20 @@
+package com.baeldung.datetime;
+
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.util.Date;
+
+public class DateUtils {
+
+    public static Date getNow() {
+        return new Date();
+    }
+
+    public static Date getDate(long millis) {
+        return new Date(millis);
+    }
+
+    public static Date getDate(String dateAsString, String pattern) throws ParseException {
+        return new SimpleDateFormat(pattern).parse(dateAsString);
+    }
+}

core-java-modules/core-java-date-operations/src/main/java/com/baeldung/datetime/sql/DateUtils.java

@@ -0,0 +1,21 @@
+package com.baeldung.datetime.sql;
+
+import java.sql.Date;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+
+public class DateUtils {
+
+    public static Date getNow() {
+        return new Date(System.currentTimeMillis());
+    }
+
+    public static Date getDate(String dateAsString) {
+        return Date.valueOf(dateAsString);
+    }
+
+    public static Date getDate(String dateAsString, String pattern) throws ParseException {
+        java.util.Date customUtilDate = new SimpleDateFormat(pattern).parse(dateAsString);
+        return new Date(customUtilDate.getTime());
+    }
+}

core-java-modules/core-java-date-operations/src/main/java/com/baeldung/datetime/sql/TimeUtils.java

@@ -0,0 +1,21 @@
+package com.baeldung.datetime.sql;
+
+import java.sql.Time;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+
+public class TimeUtils {
+
+    public static Time getNow() {
+        return new Time(System.currentTimeMillis());
+    }
+
+    public static Time getTime(String timeAsString) {
+        return Time.valueOf(timeAsString);
+    }
+
+    public static Time getTime(String dateAsString, String pattern) throws ParseException {
+        java.util.Date customUtilDate = new SimpleDateFormat(pattern).parse(dateAsString);
+        return new Time(customUtilDate.getTime());
+    }
+}

core-java-modules/core-java-date-operations/src/main/java/com/baeldung/datetime/sql/TimestampUtils.java

@@ -0,0 +1,21 @@
+package com.baeldung.datetime.sql;
+
+import java.sql.Timestamp;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+
+public class TimestampUtils {
+
+    public static Timestamp getNow() {
+        return new Timestamp(System.currentTimeMillis());
+    }
+
+    public static Timestamp getTimestamp(String timestampAsString) {
+        return Timestamp.valueOf(timestampAsString);
+    }
+
+    public static Timestamp getTimestamp(String dateAsString, String pattern) throws ParseException {
+        java.util.Date customUtilDate = new SimpleDateFormat(pattern).parse(dateAsString);
+        return new Timestamp(customUtilDate.getTime());
+    }
+}

core-java-modules/core-java-date-operations/src/test/java/com/baeldung/datetime/CalendarUtilsUnitTest.java

@@ -0,0 +1,21 @@
+package com.baeldung.datetime;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import com.baeldung.datetime.CalendarUtils;
+import com.baeldung.datetime.DateUtils;
+
+import java.text.ParseException;
+import java.util.Date;
+
+public class CalendarUtilsUnitTest {
+
+    @Test
+    public void givenDateAndDaysToAdd_thenCalendarIsCorrectlyReturned() throws ParseException {
+        Date initialDate = DateUtils.getDate("2020/01/01", "yyyy/MM/dd");
+        Date expectedDate= DateUtils.getDate("2020/01/11", "yyyy/MM/dd");
+        assertEquals(expectedDate, CalendarUtils.getPlusDays(initialDate, 10).getTime());
+    }
+}

core-java-modules/core-java-date-operations/src/test/java/com/baeldung/datetime/DateUtilsUnitTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.datetime;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import com.baeldung.datetime.DateUtils;
+
+import java.text.ParseException;
+import java.util.Date;
+
+public class DateUtilsUnitTest {
+
+    @Test
+    public void givenTimeMillis_thenDateIsReturned() {
+        Date now = DateUtils.getNow();
+        assertEquals(DateUtils.getDate(now.getTime()), now);
+    }
+
+    @Test
+    public void givenDateAndPattern_thenDateIsCorrectlyReturned() throws ParseException {
+        long milliseconds = new Date(2020 - 1900, 0, 1).getTime();
+        assertEquals(DateUtils.getDate(milliseconds), DateUtils.getDate("2020/01/01", "yyyy/MM/dd"));
+    }
+}

core-java-modules/core-java-date-operations/src/test/java/com/baeldung/datetime/sql/DateUtilsUnitTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.datetime.sql;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import com.baeldung.datetime.sql.DateUtils;
+
+import java.text.ParseException;
+import java.util.Date;
+
+public class DateUtilsUnitTest {
+
+    @Test
+    public void givenCurrentDate_thenTodayIsReturned() {
+        assertEquals(DateUtils.getNow(), new Date());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void givenDateAsString_whenPatternIsNotRespected_thenExceptionIsThrown() {
+        DateUtils.getDate("2020 01 01");
+    }
+
+    @Test
+    public void givenDateAndPattern_thenDateIsCorrectlyReturned() throws ParseException {
+        assertEquals(DateUtils.getDate("2020-01-01"), DateUtils.getDate("2020/01/01", "yyyy/MM/dd"));
+    }
+}

core-java-modules/core-java-date-operations/src/test/java/com/baeldung/datetime/sql/TimeUtilsUnitTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.datetime.sql;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import com.baeldung.datetime.sql.TimeUtils;
+
+import java.text.ParseException;
+import java.util.Date;
+
+public class TimeUtilsUnitTest {
+
+    @Test
+    public void givenCurrentTime_thenNowIsReturned() {
+        assertEquals(TimeUtils.getNow(), new Date());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void givenTimeAsString_whenPatternIsNotRespected_thenExceptionIsThrown() {
+        TimeUtils.getTime("10 11 12");
+    }
+
+    @Test
+    public void givenTimeAndPattern_thenTimeIsCorrectlyReturned() throws ParseException {
+        assertEquals(TimeUtils.getTime("10:11:12"), TimeUtils.getTime("10 11 12", "hh mm ss"));
+    }
+}

core-java-modules/core-java-date-operations/src/test/java/com/baeldung/datetime/sql/TimestampUtilsUnitTest.java

@@ -0,0 +1,29 @@
+package com.baeldung.datetime.sql;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import com.baeldung.datetime.sql.TimestampUtils;
+
+import java.text.ParseException;
+import java.util.Date;
+
+public class TimestampUtilsUnitTest {
+
+    @Test
+    public void givenCurrentTimestamp_thenNowIsReturned() {
+        assertEquals(TimestampUtils.getNow()
+            .getTime(), new Date().getTime());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void givenTimestampAsString_whenPatternIsNotRespected_thenExceptionIsThrown() {
+        TimestampUtils.getTimestamp("2020/01/01 10:11-12");
+    }
+
+    @Test
+    public void givenTimestampAndPattern_thenTimestampIsCorrectlyReturned() throws ParseException {
+        assertEquals(TimestampUtils.getTimestamp("2020-01-01 10:11:12"), TimestampUtils.getTimestamp("2020/01/01 10:11-12", "yyyy/MM/dd hh:mm-ss"));
+    }
+}