Merge remote-tracking branch 'upstream/master' into BAEL-2688

README.md

@@ -1,12 +1,16 @@
 
-The "REST with Spring" Classes
+The Courses
 ==============================
 
-Here's the Master Class of REST With Spring (along with the newly announced Boot 2 material): <br/>
-**[>> THE REST WITH SPRING - MASTER CLASS](http://www.baeldung.com/rest-with-spring-course?utm_source=github&utm_medium=social&utm_content=tutorials&utm_campaign=rws#master-class)**
 
-And here's the Master Class of Learn Spring Security: <br/>
-**[>> LEARN SPRING SECURITY - MASTER CLASS](http://www.baeldung.com/learn-spring-security-course?utm_source=github&utm_medium=social&utm_content=tutorials&utm_campaign=lss#master-class)**
+Here's the new "Learn Spring" course: <br/>
+**[>> LEARN SPRING - THE MASTER CLASS](https://www.baeldung.com/learn-spring-course?utm_source=github&utm_medium=social&utm_content=tutorials&utm_campaign=ls#master-class)**
+
+Here's the Master Class of "REST With Spring" (along with the new announced Boot 2 material): <br/>
+**[>> THE REST WITH SPRING - MASTER CLASS](https://www.baeldung.com/rest-with-spring-course?utm_source=github&utm_medium=social&utm_content=tutorials&utm_campaign=rws#master-class)**
+
+And here's the Master Class of "Learn Spring Security": <br/>
+**[>> LEARN SPRING SECURITY - MASTER CLASS](https://www.baeldung.com/learn-spring-security-course?utm_source=github&utm_medium=social&utm_content=tutorials&utm_campaign=lss#master-class)**
 
 
 
@@ -15,7 +19,7 @@ Java and Spring Tutorials
 
 This project is **a collection of small and focused tutorials** - each covering a single and well defined area of development in the Java ecosystem. 
 A strong focus of these is, of course, the Spring Framework - Spring, Spring Boot and Spring Security. 
-In additional to Spring, the following technologies are in focus: `core Java`, `Jackson`, `HttpClient`, `Guava`. 
+In additional to Spring, the modules here are covering a number of aspects in Java. 
 
 
 Building the project
@@ -32,8 +36,15 @@ Running a Spring Boot module
 ====================
 To run a Spring Boot module run the command: `mvn spring-boot:run` in the module directory
 
-###Running Tests
 
+Working with the IDE
+====================
+This repo contains a large number of modules. 
+When you're working with an individual module, there's no need to import all of them (or build all of them) - you can simply import that particular module in either Eclipse or IntelliJ. 
+
+
+Running Tests
+=============
 The command `mvn clean install` will run the unit tests in a module.
 To run the integration tests, use the command `mvn clean install -Pintegration-lite-first`
 

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/stringsortingbynumber/NaturalOrderComparators.java

@@ -0,0 +1,30 @@
+package com.baeldung.algorithms.stringsortingbynumber;
+
+import java.util.Comparator;
+
+public final class NaturalOrderComparators {
+
+    private static final String DIGIT_AND_DECIMAL_REGEX = "[^\\d.]";
+
+    private NaturalOrderComparators() {
+        throw new AssertionError("Let's keep this static");
+    }
+
+    public static Comparator<String> createNaturalOrderRegexComparator() {
+        return Comparator.comparingDouble(NaturalOrderComparators::parseStringToNumber);
+    }
+
+    private static double parseStringToNumber(String input){
+
+        final String digitsOnly = input.replaceAll(DIGIT_AND_DECIMAL_REGEX, "");
+
+        if("".equals(digitsOnly)) return 0;
+
+        try{
+            return Double.parseDouble(digitsOnly);
+        }catch (NumberFormatException nfe){
+            return 0;
+        }
+    }
+
+}

algorithms-miscellaneous-3/src/test/java/com/baeldung/algorithms/stringsortingbynumber/NaturalOrderComparatorsUnitTest.java

@@ -0,0 +1,79 @@
+package com.baeldung.algorithms.stringsortingbynumber;
+
+import com.baeldung.algorithms.stringsortingbynumber.NaturalOrderComparators;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.Assert.*;
+
+public class NaturalOrderComparatorsUnitTest {
+
+    @Test
+    public void givenSimpleStringsContainingIntsAndDoubles_whenSortedByRegex_checkSortingCorrect() {
+
+        List<String> testStrings = Arrays.asList("a1", "b3", "c4", "d2.2", "d2.4", "d2.3d");
+
+        testStrings.sort(NaturalOrderComparators.createNaturalOrderRegexComparator());
+
+        List<String> expected = Arrays.asList("a1", "d2.2", "d2.3d", "d2.4", "b3", "c4");
+
+        assertEquals(expected, testStrings);
+
+
+    }
+
+    @Test
+    public void givenSimpleStringsContainingIntsAndDoublesWithAnInvalidNumber_whenSortedByRegex_checkSortingCorrect() {
+
+        List<String> testStrings = Arrays.asList("a1", "b3", "c4", "d2.2", "d2.4", "d2.3.3d");
+
+        testStrings.sort(NaturalOrderComparators.createNaturalOrderRegexComparator());
+
+        List<String> expected = Arrays.asList("d2.3.3d", "a1", "d2.2", "d2.4", "b3", "c4");
+
+        assertEquals(expected, testStrings);
+
+
+    }
+
+    @Test
+    public void givenAllForseenProblems_whenSortedByRegex_checkSortingCorrect() {
+
+        List<String> testStrings = Arrays.asList("a1", "b3", "c4", "d2.2", "d2.f4", "d2.3.3d");
+
+        testStrings.sort(NaturalOrderComparators.createNaturalOrderRegexComparator());
+
+        List<String> expected = Arrays.asList("d2.3.3d", "a1", "d2.2", "d2.f4", "b3", "c4");
+
+        assertEquals(expected, testStrings);
+
+
+    }
+
+    @Test
+    public void givenComplexStringsContainingSeparatedNumbers_whenSortedByRegex_checkNumbersCondensedAndSorted() {
+
+        List<String> testStrings = Arrays.asList("a1b2c5", "b3ght3.2", "something65.thensomething5"); //125, 33.2, 65.5
+
+        List<String> expected = Arrays.asList("b3ght3.2", "something65.thensomething5", "a1b2c5" );
+
+        testStrings.sort(NaturalOrderComparators.createNaturalOrderRegexComparator());
+
+        assertEquals(expected, testStrings);
+
+    }
+
+    @Test
+    public void givenStringsNotContainingNumbers_whenSortedByRegex_checkOrderNotChanged() {
+
+        List<String> testStrings = Arrays.asList("a", "c", "d", "e");
+        List<String> expected = new ArrayList<>(testStrings);
+
+        testStrings.sort(NaturalOrderComparators.createNaturalOrderRegexComparator());
+
+        assertEquals(expected, testStrings);
+    }
+}

algorithms-sorting/src/main/java/com/baeldung/algorithms/shellsort/ShellSort.java

@@ -0,0 +1,20 @@
+package com.baeldung.algorithms.shellsort;
+
+public class ShellSort {
+
+    public static void sort(int arrayToSort[]) {
+        int n = arrayToSort.length;
+
+        for (int gap = n / 2; gap > 0; gap /= 2) {
+            for (int i = gap; i < n; i++) {
+                int key = arrayToSort[i];
+                int j = i;
+                while (j >= gap && arrayToSort[j - gap] > key) {
+                    arrayToSort[j] = arrayToSort[j - gap];
+                    j -= gap;
+                }
+                arrayToSort[j] = key;
+            }
+        }
+    }
+}

algorithms-sorting/src/test/java/com/baeldung/algorithms/shellsort/ShellSortUnitTest.java

@@ -0,0 +1,17 @@
+package com.baeldung.algorithms.shellsort;
+
+import static org.junit.Assert.*;
+import static org.junit.Assert.assertArrayEquals;
+
+import org.junit.Test;
+
+public class ShellSortUnitTest {
+
+    @Test
+    public void givenUnsortedArray_whenShellSort_thenSortedAsc() {
+        int[] input = {41, 15, 82, 5, 65, 19, 32, 43, 8};
+        ShellSort.sort(input);
+        int[] expected = {5, 8, 15, 19, 32, 41, 43, 65, 82};
+        assertArrayEquals("the two arrays are not equal", expected, input);
+    }
+}

axon/pom.xml

@@ -18,12 +18,6 @@
             <groupId>org.axonframework</groupId>
             <artifactId>axon-spring-boot-starter</artifactId>
             <version>${axon.version}</version>
-            <exclusions>
-                <exclusion>
-                    <groupId>org.axonframework</groupId>
-                    <artifactId>axon-server-connector</artifactId>
-                </exclusion>
-            </exclusions>
         </dependency>
 
         <dependency>
@@ -58,7 +52,7 @@
     </dependencies>
 
     <properties>
-        <axon.version>4.0.3</axon.version>
+        <axon.version>4.1.2</axon.version>
     </properties>
 
 </project>

axon/src/main/java/com/baeldung/axon/commandmodel/OrderAggregate.java

@@ -13,6 +13,7 @@ import com.baeldung.axon.coreapi.commands.ShipOrderCommand;
 import com.baeldung.axon.coreapi.events.OrderConfirmedEvent;
 import com.baeldung.axon.coreapi.events.OrderPlacedEvent;
 import com.baeldung.axon.coreapi.events.OrderShippedEvent;
+import com.baeldung.axon.coreapi.exceptions.UnconfirmedOrderException;
 
 @Aggregate
 public class OrderAggregate {
@@ -34,7 +35,7 @@ public class OrderAggregate {
     @CommandHandler
     public void handle(ShipOrderCommand command) {
         if (!orderConfirmed) {
-            throw new IllegalStateException("Cannot ship an order which has not been confirmed yet.");
+            throw new UnconfirmedOrderException();
         }
 
         apply(new OrderShippedEvent(orderId));
@@ -43,12 +44,12 @@ public class OrderAggregate {
     @EventSourcingHandler
     public void on(OrderPlacedEvent event) {
         this.orderId = event.getOrderId();
-        orderConfirmed = false;
+        this.orderConfirmed = false;
     }
 
     @EventSourcingHandler
     public void on(OrderConfirmedEvent event) {
-        orderConfirmed = true;
+        this.orderConfirmed = true;
     }
 
     protected OrderAggregate() {

axon/src/main/java/com/baeldung/axon/coreapi/exceptions/UnconfirmedOrderException.java

@@ -0,0 +1,8 @@
+package com.baeldung.axon.coreapi.exceptions;
+
+public class UnconfirmedOrderException extends IllegalStateException {
+
+    public UnconfirmedOrderException() {
+        super("Cannot ship an order which has not been confirmed yet.");
+    }
+}

axon/src/main/java/com/baeldung/axon/querymodel/OrderedProductsEventHandler.java

@@ -5,6 +5,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+import org.axonframework.config.ProcessingGroup;
 import org.axonframework.eventhandling.EventHandler;
 import org.axonframework.queryhandling.QueryHandler;
 import org.springframework.stereotype.Service;
@@ -16,6 +17,7 @@ import com.baeldung.axon.coreapi.queries.FindAllOrderedProductsQuery;
 import com.baeldung.axon.coreapi.queries.OrderedProduct;
 
 @Service
+@ProcessingGroup("ordered-products")
 public class OrderedProductsEventHandler {
 
     private final Map<String, OrderedProduct> orderedProducts = new HashMap<>();

axon/src/main/resources/application.properties

@@ -0,0 +1 @@
+spring.application.name=Order Management Service

axon/src/test/java/com/baeldung/axon/commandmodel/OrderAggregateUnitTest.java

@@ -2,6 +2,7 @@ package com.baeldung.axon.commandmodel;
 
 import java.util.UUID;
 
+import com.baeldung.axon.coreapi.exceptions.UnconfirmedOrderException;
 import org.axonframework.test.aggregate.AggregateTestFixture;
 import org.axonframework.test.aggregate.FixtureConfiguration;
 import org.junit.*;
@@ -41,12 +42,12 @@ public class OrderAggregateUnitTest {
     }
 
     @Test
-    public void givenOrderPlacedEvent_whenShipOrderCommand_thenShouldThrowIllegalStateException() {
+    public void givenOrderPlacedEvent_whenShipOrderCommand_thenShouldThrowUnconfirmedOrderException() {
         String orderId = UUID.randomUUID().toString();
         String product = "Deluxe Chair";
         fixture.given(new OrderPlacedEvent(orderId, product))
                .when(new ShipOrderCommand(orderId))
-               .expectException(IllegalStateException.class);
+               .expectException(UnconfirmedOrderException.class);
     }
 
     @Test

core-java-modules/core-java-12/README.md

@@ -1,3 +1,4 @@
-## Relevant articles:
+## Relevant Articles:
+
 
 - [String API Updates in Java 12](https://www.baeldung.com/java12-string-api)

core-java-modules/core-java-arrays-2/.gitignore

@@ -0,0 +1,25 @@
+*.class
+
+0.*
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+.resourceCache
+
+# Packaged files #
+*.jar
+*.war
+*.ear
+
+# Files generated by integration tests
+backup-pom.xml
+/bin/
+/temp
+
+#IntelliJ specific
+.idea/
+*.iml

core-java-modules/core-java-arrays-2/pom.xml

@@ -0,0 +1,50 @@
+<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>
+    <groupId>com.baeldung</groupId>
+    <artifactId>core-java-arrays-2</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-arrays-2</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+        <!-- test scoped -->
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-arrays-2</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+
+        <!-- util -->
+        <commons-lang3.version>3.9</commons-lang3.version>
+        <!-- testing -->
+        <assertj-core.version>3.10.0</assertj-core.version>
+    </properties>
+
+</project>

core-java-modules/core-java-arrays-2/src/main/java/com/baeldung/array/looping/LoopDiagonally.java

@@ -0,0 +1,45 @@
+package com.baeldung.array.looping;
+
+public class LoopDiagonally {
+
+
+    public String loopDiagonally(String[][] twoDArray) {
+
+        int length = twoDArray.length;
+        int diagonalLines = (length + length) - 1;
+        int itemsInDiagonal = 0;
+        int midPoint = (diagonalLines / 2) + 1;
+        StringBuilder output = new StringBuilder();
+
+        for (int i = 1; i <= diagonalLines; i++) {
+
+            StringBuilder items = new StringBuilder();
+            int rowIndex;
+            int columnIndex;
+
+            if (i <= midPoint) {
+                itemsInDiagonal++;
+                for (int j = 0; j < itemsInDiagonal; j++) {
+                    rowIndex = (i - j) - 1;
+                    columnIndex = j;
+                    items.append(twoDArray[rowIndex][columnIndex]);
+                }
+            } else {
+                itemsInDiagonal--;
+                for (int j = 0; j < itemsInDiagonal; j++) {
+                    rowIndex = (length - 1) - j;
+                    columnIndex = (i - length) + j;
+                    items.append(twoDArray[rowIndex][columnIndex]);
+                }
+            }
+
+            if (i != diagonalLines) {
+                output.append(items).append(" ");
+            } else {
+                output.append(items);
+            }
+        }
+
+        return output.toString();
+    }
+}

core-java-modules/core-java-arrays-2/src/test/java/com/baeldung/array/looping/LoopDiagonallyUnitTest.java

@@ -0,0 +1,20 @@
+package com.baeldung.array.looping;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class LoopDiagonallyUnitTest {
+
+    @Test
+    public void twoArrayIsLoopedDiagonallyAsExpected() {
+
+        LoopDiagonally loopDiagonally = new LoopDiagonally();
+        String[][] twoDArray = {{"a", "b", "c"},
+                                {"d", "e", "f"},
+                                {"g", "h", "i"}};
+
+        String output = loopDiagonally.loopDiagonally(twoDArray);
+        assertEquals("a db gec hf i", output);
+    }
+}

core-java-modules/core-java-arrays/src/main/java/com/baeldung/array/SortedArrayChecker.java

@@ -2,7 +2,10 @@ package com.baeldung.array;
 
 import com.baeldung.arraycopy.model.Employee;
 
+import java.util.Comparator;
+
 public class SortedArrayChecker {
+
     boolean isSorted(int[] array, int length) {
         if (array == null || length < 2)
             return true;
@@ -22,7 +25,7 @@ public class SortedArrayChecker {
         return true;
     }
 
-    boolean isSorted(String[] array, int length) {
+    boolean isSorted(Comparable[] array, int length) {
         if (array == null || length < 2)
             return true;
 
@@ -32,40 +35,31 @@ public class SortedArrayChecker {
         return isSorted(array, length - 1);
     }
 
-boolean isSorted(String[] array) {
-    for (int i = 0; i < array.length - 1; ++i) {
-        if (array[i].compareTo(array[i + 1]) > 0)
-            return false;
-    }
-
-    return true;
-}
-
-    boolean isSortedByName(Employee[] array) {
+    boolean isSorted(Comparable[] array) {
         for (int i = 0; i < array.length - 1; ++i) {
-            if (array[i].getName().compareTo(array[i + 1].getName()) > 0)
+            if (array[i].compareTo(array[i + 1]) > 0)
                 return false;
         }
 
         return true;
     }
 
-boolean isSortedByAge(Employee[] array) {
-    for (int i = 0; i < array.length - 1; ++i) {
-        if (array[i].getAge() > (array[i + 1].getAge()))
-            return false;
+    boolean isSorted(Object[] array, Comparator comparator) {
+        for (int i = 0; i < array.length - 1; ++i) {
+            if (comparator.compare(array[i], (array[i + 1])) > 0)
+                return false;
+        }
+
+        return true;
     }
 
-    return true;
-}
-
-    boolean isSortedByAge(Employee[] array, int length) {
+    boolean isSorted(Object[] array, Comparator comparator, int length) {
         if (array == null || length < 2)
             return true;
 
-        if (array[length - 2].getAge() > array[length - 1].getAge())
+        if (comparator.compare(array[length - 2], array[length - 1]) > 0)
             return false;
 
-        return isSortedByAge(array, length - 1);
+        return isSorted(array, comparator, length - 1);
     }
 }

core-java-modules/core-java-arrays/src/test/java/com/baeldung/array/SortedArrayCheckerUnitTest.java

@@ -4,32 +4,33 @@ import com.baeldung.arraycopy.model.Employee;
 import org.junit.Before;
 import org.junit.Test;
 
+import java.util.Comparator;
+
 import static org.assertj.core.api.Assertions.assertThat;
 
-class SortedArrayCheckerUnitTest {
-
+public class SortedArrayCheckerUnitTest {
     private static final int[] INTEGER_SORTED = {1, 3, 5, 7, 9};
     private static final int[] INTEGER_NOT_SORTED = {1, 3, 11, 7};
 
     private static final String[] STRING_SORTED = {"abc", "cde", "fgh"};
     private static final String[] STRING_NOT_SORTED = {"abc", "fgh", "cde", "ijk"};
 
-    private final Employee[] EMPLOYEES_SORTED_BY_NAME = {
+    private static final Employee[] EMPLOYEES_SORTED_BY_NAME = {
             new Employee(1, "Carlos", 26),
             new Employee(2, "Daniel", 31),
             new Employee(3, "Marta", 27)};
 
-    private final Employee[] EMPLOYEES_NOT_SORTED_BY_NAME = {
+    private static final Employee[] EMPLOYEES_NOT_SORTED_BY_NAME = {
             new Employee(1, "Daniel", 31),
             new Employee(2, "Carlos", 26),
             new Employee(3, "Marta", 27)};
 
-    private final Employee[] EMPLOYEES_SORTED_BY_AGE = {
+    private static final Employee[] EMPLOYEES_SORTED_BY_AGE = {
             new Employee(1, "Carlos", 26),
             new Employee(2, "Marta", 27),
             new Employee(3, "Daniel", 31)};
 
-    private final Employee[] EMPLOYEES_NOT_SORTED_BY_AGE = {
+    private static final Employee[] EMPLOYEES_NOT_SORTED_BY_AGE = {
             new Employee(1, "Marta", 27),
             new Employee(2, "Carlos", 26),
             new Employee(3, "Daniel", 31)};
@@ -61,13 +62,18 @@ class SortedArrayCheckerUnitTest {
 
     @Test
     public void givenEmployeeArray_thenReturnIfItIsSortedOrNot() {
-        assertThat(sortedArrayChecker.isSortedByName(EMPLOYEES_SORTED_BY_NAME)).isEqualTo(true);
-        assertThat(sortedArrayChecker.isSortedByName(EMPLOYEES_NOT_SORTED_BY_NAME)).isEqualTo(false);
+        assertThat(sortedArrayChecker.isSorted(EMPLOYEES_SORTED_BY_NAME, Comparator.comparing(Employee::getName))).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSorted(EMPLOYEES_NOT_SORTED_BY_NAME, Comparator.comparing(Employee::getName))).isEqualTo(false);
 
-        assertThat(sortedArrayChecker.isSortedByAge(EMPLOYEES_SORTED_BY_AGE)).isEqualTo(true);
-        assertThat(sortedArrayChecker.isSortedByAge(EMPLOYEES_NOT_SORTED_BY_AGE)).isEqualTo(false);
+        assertThat(sortedArrayChecker.isSorted(EMPLOYEES_SORTED_BY_AGE, Comparator.comparingInt(Employee::getAge))).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSorted(EMPLOYEES_NOT_SORTED_BY_AGE, Comparator.comparingInt(Employee::getAge))).isEqualTo(false);
 
-        assertThat(sortedArrayChecker.isSortedByAge(EMPLOYEES_SORTED_BY_AGE, EMPLOYEES_SORTED_BY_AGE.length)).isEqualTo(true);
-        assertThat(sortedArrayChecker.isSortedByAge(EMPLOYEES_NOT_SORTED_BY_AGE, EMPLOYEES_NOT_SORTED_BY_AGE.length)).isEqualTo(false);
+        assertThat(sortedArrayChecker
+                .isSorted(EMPLOYEES_SORTED_BY_AGE, Comparator.comparingInt(Employee::getAge), EMPLOYEES_SORTED_BY_AGE.length))
+                .isEqualTo(true);
+        assertThat(sortedArrayChecker
+                .isSorted(EMPLOYEES_NOT_SORTED_BY_AGE, Comparator.comparingInt(Employee::getAge), EMPLOYEES_NOT_SORTED_BY_AGE.length))
+                .isEqualTo(false);
     }
+
 }

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

@@ -1,3 +1,3 @@
-## Relevant articles:
+## Relevant Articles:
 
 - [Will an Error Be Caught by Catch Block in Java?](https://www.baeldung.com/java-error-catch)

core-java-modules/core-java-io/src/main/java/com/baeldung/files/Main.java

@@ -0,0 +1,24 @@
+package com.baeldung.files;
+
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingApacheCommonsIO;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingBufferedReader;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingGoogleGuava;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingLineNumberReader;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingNIOFileChannel;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingNIOFiles;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingScanner;
+
+public class Main {
+
+    private static final String INPUT_FILE_NAME = "src/main/resources/input.txt";
+
+    public static void main(String... args) throws Exception {
+        System.out.printf("Total Number of Lines Using BufferedReader: %s%n", getTotalNumberOfLinesUsingBufferedReader(INPUT_FILE_NAME));
+        System.out.printf("Total Number of Lines Using LineNumberReader: %s%n", getTotalNumberOfLinesUsingLineNumberReader(INPUT_FILE_NAME));
+        System.out.printf("Total Number of Lines Using Scanner: %s%n", getTotalNumberOfLinesUsingScanner(INPUT_FILE_NAME));
+        System.out.printf("Total Number of Lines Using NIO Files: %s%n", getTotalNumberOfLinesUsingNIOFiles(INPUT_FILE_NAME));
+        System.out.printf("Total Number of Lines Using NIO FileChannel: %s%n", getTotalNumberOfLinesUsingNIOFileChannel(INPUT_FILE_NAME));
+        System.out.printf("Total Number of Lines Using Apache Commons IO: %s%n", getTotalNumberOfLinesUsingApacheCommonsIO(INPUT_FILE_NAME));
+        System.out.printf("Total Number of Lines Using NIO Google Guava: %s%n", getTotalNumberOfLinesUsingGoogleGuava(INPUT_FILE_NAME));
+    }
+}

core-java-modules/core-java-io/src/main/java/com/baeldung/files/NumberOfLineFinder.java

@@ -0,0 +1,112 @@
+package com.baeldung.files;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileReader;
+import java.io.IOException;
+import java.io.LineNumberReader;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.channels.FileChannel.MapMode;
+import java.nio.charset.Charset;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.nio.file.StandardOpenOption;
+import java.util.List;
+import java.util.Scanner;
+import java.util.stream.Stream;
+
+import org.apache.commons.io.FileUtils;
+import org.apache.commons.io.LineIterator;
+
+public class NumberOfLineFinder {
+
+    public static int getTotalNumberOfLinesUsingBufferedReader(String fileName) {
+        int lines = 0;
+        try (BufferedReader reader = new BufferedReader(new FileReader(fileName))) {
+            while (reader.readLine() != null) {
+                lines++;
+            }
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+    public static int getTotalNumberOfLinesUsingLineNumberReader(String fileName) {
+        int lines = 0;
+        try (LineNumberReader reader = new LineNumberReader(new FileReader(fileName))) {
+            reader.skip(Integer.MAX_VALUE);
+            lines = reader.getLineNumber() + 1;
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+    public static int getTotalNumberOfLinesUsingScanner(String fileName) {
+        int lines = 0;
+        try (Scanner scanner = new Scanner(new FileReader(fileName))) {
+            while (scanner.hasNextLine()) {
+                scanner.nextLine();
+                lines++;
+            }
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+    public static int getTotalNumberOfLinesUsingNIOFiles(String fileName) {
+        int lines = 0;
+        try (Stream<String> fileStream = Files.lines(Paths.get(fileName))) {
+            lines = (int) fileStream.count();
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+    public static int getTotalNumberOfLinesUsingNIOFileChannel(String fileName) {
+        int lines = 1;
+        try (FileChannel channel = FileChannel.open(Paths.get(fileName), StandardOpenOption.READ)) {
+            ByteBuffer byteBuffer = channel.map(MapMode.READ_ONLY, 0, channel.size());
+            while (byteBuffer.hasRemaining()) {
+                byte currentChar = byteBuffer.get();
+                if (currentChar == '\n') {
+                    lines++;
+                }
+            }
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+    public static int getTotalNumberOfLinesUsingApacheCommonsIO(String fileName) {
+        int lines = 0;
+        try {
+            LineIterator lineIterator = FileUtils.lineIterator(new File(fileName));
+            while (lineIterator.hasNext()) {
+                lineIterator.nextLine();
+                lines++;
+            }
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+    public static int getTotalNumberOfLinesUsingGoogleGuava(String fileName) {
+        int lines = 0;
+        try {
+            List<String> lineItems = com.google.common.io.Files.readLines(Paths.get(fileName)
+                .toFile(), Charset.defaultCharset());
+            lines = lineItems.size();
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+}

core-java-modules/core-java-io/src/test/java/com/baeldung/file/NumberOfLineFinderUnitTest.java

@@ -0,0 +1,60 @@
+package com.baeldung.file;
+
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingApacheCommonsIO;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingBufferedReader;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingGoogleGuava;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingLineNumberReader;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingNIOFileChannel;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingNIOFiles;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingScanner;
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class NumberOfLineFinderUnitTest {
+    private static final String INPUT_FILE_NAME = "src/main/resources/input.txt";
+    private static final int ACTUAL_LINE_COUNT = 45;
+
+    @Test
+    public void whenUsingBufferedReader_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingBufferedReader(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+    @Test
+    public void whenUsingLineNumberReader_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingLineNumberReader(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+    @Test
+    public void whenUsingScanner_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingScanner(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+    @Test
+    public void whenUsingNIOFiles_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingNIOFiles(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+    @Test
+    public void whenUsingNIOFileChannel_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingNIOFileChannel(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+    @Test
+    public void whenUsingApacheCommonsIO_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingApacheCommonsIO(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+    @Test
+    public void whenUsingGoogleGuava_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingGoogleGuava(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/aggregation/Car.java

@@ -0,0 +1,9 @@
+package com.baeldung.relationships.aggregation;
+
+import java.util.List;
+
+public class Car {
+
+    private List<Wheel> wheels;
+    
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/aggregation/CarWithStaticInnerWheel.java

@@ -0,0 +1,13 @@
+package com.baeldung.relationships.aggregation;
+
+import java.util.List;
+
+public class CarWithStaticInnerWheel {
+
+    private List<Wheel> wheels;
+
+    public static class Wheel {
+
+    }
+
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/aggregation/Wheel.java

@@ -0,0 +1,7 @@
+package com.baeldung.relationships.aggregation;
+
+public class Wheel {
+
+    private Car car;
+    
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/association/Child.java

@@ -0,0 +1,7 @@
+package com.baeldung.relationships.association;
+
+public class Child {
+
+    private Mother mother;
+
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/association/Mother.java

@@ -0,0 +1,9 @@
+package com.baeldung.relationships.association;
+
+import java.util.List;
+
+public class Mother {
+
+    private List<Child> children;
+
+}