Merge pull request #7 from eugenp/master

update master

algorithms-miscellaneous-3/pom.xml

@@ -18,6 +18,18 @@
             <version>${org.assertj.core.version}</version>
             <scope>test</scope>
         </dependency>
+        
+        <dependency>
+        	<groupId>org.apache.commons</groupId>
+        	<artifactId>commons-collections4</artifactId>
+        	<version>${commons-collections4.version}</version>
+        </dependency>
+        
+        <dependency>
+        	<groupId>com.google.guava</groupId>
+        	<artifactId>guava</artifactId>
+        	<version>${guava.version}</version>
+        </dependency>
     </dependencies>
 
     <build>
@@ -34,6 +46,7 @@
 
     <properties>
         <org.assertj.core.version>3.9.0</org.assertj.core.version>
+        <commons-collections4.version>4.3</commons-collections4.version>
+        <guava.version>28.0-jre</guava.version>
     </properties>
-
 </project>

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/checksortedlist/Employee.java

@@ -0,0 +1,34 @@
+package com.baeldung.algorithms.checksortedlist;
+
+public class Employee {
+
+    long id;
+
+    String name;
+
+    public Employee() {
+    }
+
+    public Employee(long id, String name) {
+        super();
+        this.id = id;
+        this.name = name;
+    }
+
+    public long getId() {
+        return id;
+    }
+
+    public void setId(long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/checksortedlist/SortedListChecker.java

@@ -0,0 +1,85 @@
+package com.baeldung.algorithms.checksortedlist;
+
+import static org.apache.commons.collections4.CollectionUtils.isEmpty;
+
+import java.util.Comparator;
+import java.util.Iterator;
+import java.util.List;
+
+import com.google.common.collect.Comparators;
+import com.google.common.collect.Ordering;;
+
+public class SortedListChecker {
+
+    private SortedListChecker() {
+        throw new AssertionError();
+    }
+
+    public static boolean checkIfSortedUsingIterativeApproach(List<String> listOfStrings) {
+        if (isEmpty(listOfStrings) || listOfStrings.size() == 1) {
+            return true;
+        }
+
+        Iterator<String> iter = listOfStrings.iterator();
+        String current, previous = iter.next();
+        while (iter.hasNext()) {
+            current = iter.next();
+            if (previous.compareTo(current) > 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    public static boolean checkIfSortedUsingIterativeApproach(List<Employee> employees, Comparator<Employee> employeeComparator) {
+        if (isEmpty(employees) || employees.size() == 1) {
+            return true;
+        }
+
+        Iterator<Employee> iter = employees.iterator();
+        Employee current, previous = iter.next();
+        while (iter.hasNext()) {
+            current = iter.next();
+            if (employeeComparator.compare(previous, current) > 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    public static boolean checkIfSortedUsingRecursion(List<String> listOfStrings) {
+        return isSortedRecursive(listOfStrings, listOfStrings.size());
+    }
+
+    public static boolean isSortedRecursive(List<String> listOfStrings, int index) {
+        if (index < 2) {
+            return true;
+        } else if (listOfStrings.get(index - 2)
+            .compareTo(listOfStrings.get(index - 1)) > 0) {
+            return false;
+        } else {
+            return isSortedRecursive(listOfStrings, index - 1);
+        }
+    }
+
+    public static boolean checkIfSortedUsingOrderingClass(List<String> listOfStrings) {
+        return Ordering.<String> natural()
+            .isOrdered(listOfStrings);
+    }
+
+    public static boolean checkIfSortedUsingOrderingClass(List<Employee> employees, Comparator<Employee> employeeComparator) {
+        return Ordering.from(employeeComparator)
+            .isOrdered(employees);
+    }
+
+    public static boolean checkIfSortedUsingOrderingClassHandlingNull(List<String> listOfStrings) {
+        return Ordering.<String> natural()
+            .nullsLast()
+            .isOrdered(listOfStrings);
+    }
+
+    public static boolean checkIfSortedUsingComparators(List<String> listOfStrings) {
+        return Comparators.isInOrder(listOfStrings, Comparator.<String> naturalOrder());
+    }
+
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/folding/FoldingHash.java

@@ -0,0 +1,78 @@
+package com.baeldung.folding;
+
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+/**
+ * Calculate a hash value for the strings using the folding technique.
+ * 
+ * The implementation serves only to the illustration purposes and is far
+ * from being the most efficient. 
+ * 
+ * @author A.Shcherbakov
+ *
+ */
+public class FoldingHash {
+
+    /**
+     * Calculate the hash value of a given string.
+     * 
+     * @param str Assume it is not null
+     * @param groupSize the group size in the folding technique
+     * @param maxValue defines a max value that the hash may acquire (exclusive)     
+     * @return integer value from 0 (inclusive) to maxValue (exclusive)
+     */
+    public int hash(String str, int groupSize, int maxValue) {
+        final int[] codes = this.toAsciiCodes(str);
+        return IntStream.range(0, str.length())
+            .filter(i -> i % groupSize == 0)
+            .mapToObj(i -> extract(codes, i, groupSize))
+            .map(block -> concatenate(block))
+            .reduce(0, (a, b) -> (a + b) % maxValue);
+    }
+
+    /**
+     * Returns a new array of given length whose elements are take from 
+     * the original one starting from the offset.
+     *  
+     * If the original array has not enough elements, the returning array will contain 
+     * element from the offset till the end of the original array.
+     *  
+     * @param numbers original array. Assume it is not null.
+     * @param offset index of the element to start from. Assume it is less than the size of the array 
+     * @param length max size of the resulting array
+     * @return
+     */
+    public int[] extract(int[] numbers, int offset, int length) {
+        final int defect = numbers.length - (offset + length);
+        final int s = defect < 0 ? length + defect : length;
+        int[] result = new int[s];
+        for (int index = 0; index < s; index++) {
+            result[index] = numbers[index + offset];
+        }
+        return result;
+    }
+
+    /**
+     * Concatenate the numbers into a single number as if they were strings.
+     * Assume that the procedure does not suffer from the overflow.
+     * @param numbers integers to concatenate
+     * @return
+     */
+    public int concatenate(int[] numbers) {
+        final String merged = IntStream.of(numbers)
+            .mapToObj(number -> "" + number)
+            .collect(Collectors.joining());
+        return Integer.parseInt(merged, 10);
+    }
+
+    /**
+     * Convert the string into its characters' ASCII codes.
+     * @param str input string
+     * @return
+     */
+    private int[] toAsciiCodes(String str) {
+        return str.chars()
+            .toArray();
+    }
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/folding/Main.java

@@ -0,0 +1,17 @@
+package com.baeldung.folding;
+
+/**
+ * Code snippet for article "A Guide to the Folding Technique".
+ *  
+ * @author A.Shcherbakov
+ *
+ */
+public class Main {
+
+    public static void main(String... arg) {
+        FoldingHash hasher = new FoldingHash();
+        final String str = "Java language";
+        System.out.println(hasher.hash(str, 2, 100_000));
+        System.out.println(hasher.hash(str, 3, 1_000));
+    }
+}

algorithms-miscellaneous-3/src/test/java/com/baeldung/algorithms/checksortedlist/SortedListCheckerUnitTest.java

@@ -0,0 +1,106 @@
+package com.baeldung.algorithms.checksortedlist;
+
+import static com.baeldung.algorithms.checksortedlist.SortedListChecker.checkIfSortedUsingComparators;
+import static com.baeldung.algorithms.checksortedlist.SortedListChecker.checkIfSortedUsingIterativeApproach;
+import static com.baeldung.algorithms.checksortedlist.SortedListChecker.checkIfSortedUsingOrderingClass;
+import static com.baeldung.algorithms.checksortedlist.SortedListChecker.checkIfSortedUsingRecursion;
+import static java.util.Arrays.asList;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+import org.junit.Before;
+import org.junit.Test;
+
+public class SortedListCheckerUnitTest {
+
+    private List<String> sortedListOfString;
+    private List<String> unsortedListOfString;
+    private List<String> singletonList;
+
+    private List<Employee> employeesSortedByName;
+    private List<Employee> employeesNotSortedByName;
+
+    @Before
+    public void setUp() {
+        sortedListOfString = asList("Canada", "HK", "LA", "NJ", "NY");
+        unsortedListOfString = asList("LA", "HK", "NJ", "NY", "Canada");
+        singletonList = Collections.singletonList("NY");
+
+        employeesSortedByName = asList(new Employee(1L, "John"), new Employee(2L, "Kevin"), new Employee(3L, "Mike"));
+        employeesNotSortedByName = asList(new Employee(1L, "Kevin"), new Employee(2L, "John"), new Employee(3L, "Mike"));
+    }
+
+    @Test
+    public void givenSortedList_whenUsingIterativeApproach_thenReturnTrue() {
+        assertThat(checkIfSortedUsingIterativeApproach(sortedListOfString)).isTrue();
+    }
+
+    @Test
+    public void givenSingleElementList_whenUsingIterativeApproach_thenReturnTrue() {
+        assertThat(checkIfSortedUsingIterativeApproach(singletonList)).isTrue();
+    }
+
+    @Test
+    public void givenUnsortedList_whenUsingIterativeApproach_thenReturnFalse() {
+        assertThat(checkIfSortedUsingIterativeApproach(unsortedListOfString)).isFalse();
+    }
+
+    @Test
+    public void givenSortedListOfEmployees_whenUsingIterativeApproach_thenReturnTrue() {
+        assertThat(checkIfSortedUsingIterativeApproach(employeesSortedByName, Comparator.comparing(Employee::getName))).isTrue();
+    }
+
+    @Test
+    public void givenUnsortedListOfEmployees_whenUsingIterativeApproach_thenReturnFalse() {
+        assertThat(checkIfSortedUsingIterativeApproach(employeesNotSortedByName, Comparator.comparing(Employee::getName))).isFalse();
+    }
+
+    @Test
+    public void givenSortedList_whenUsingRecursion_thenReturnTrue() {
+        assertThat(checkIfSortedUsingRecursion(sortedListOfString)).isTrue();
+    }
+
+    @Test
+    public void givenSingleElementList_whenUsingRecursion_thenReturnTrue() {
+        assertThat(checkIfSortedUsingRecursion(singletonList)).isTrue();
+    }
+
+    @Test
+    public void givenUnsortedList_whenUsingRecursion_thenReturnFalse() {
+        assertThat(checkIfSortedUsingRecursion(unsortedListOfString)).isFalse();
+    }
+
+    @Test
+    public void givenSortedList_whenUsingGuavaOrdering_thenReturnTrue() {
+        assertThat(checkIfSortedUsingOrderingClass(sortedListOfString)).isTrue();
+    }
+
+    @Test
+    public void givenUnsortedList_whenUsingGuavaOrdering_thenReturnFalse() {
+        assertThat(checkIfSortedUsingOrderingClass(unsortedListOfString)).isFalse();
+    }
+
+    @Test
+    public void givenSortedListOfEmployees_whenUsingGuavaOrdering_thenReturnTrue() {
+        assertThat(checkIfSortedUsingOrderingClass(employeesSortedByName, Comparator.comparing(Employee::getName))).isTrue();
+    }
+
+    @Test
+    public void givenUnsortedListOfEmployees_whenUsingGuavaOrdering_thenReturnFalse() {
+        assertThat(checkIfSortedUsingOrderingClass(employeesNotSortedByName, Comparator.comparing(Employee::getName))).isFalse();
+    }
+
+    @Test
+    public void givenSortedList_whenUsingGuavaComparators_thenReturnTrue() {
+        assertThat(checkIfSortedUsingComparators(sortedListOfString)).isTrue();
+    }
+
+    @Test
+    public void givenUnsortedList_whenUsingGuavaComparators_thenReturnFalse() {
+        assertThat(checkIfSortedUsingComparators(unsortedListOfString)).isFalse();
+    }
+
+}

algorithms-miscellaneous-3/src/test/java/com/baeldung/folding/FoldingHashUnitTest.java

@@ -0,0 +1,54 @@
+package com.baeldung.folding;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class FoldingHashUnitTest {
+
+    @Test
+    public void givenStringJavaLanguage_whenSize2Capacity100000_then48933() throws Exception {
+        final FoldingHash hasher = new FoldingHash();
+        final int value = hasher.hash("Java language", 2, 100_000);
+        assertEquals(value, 48933);
+    }
+
+    @Test
+    public void givenStringVaJaLanguage_whenSize2Capacity100000_thenSameAsJavaLanguage() throws Exception {
+        final FoldingHash hasher = new FoldingHash();
+        final int java = hasher.hash("Java language", 2, 100_000);
+        final int vaja = hasher.hash("vaJa language", 2, 100_000);
+        assertTrue(java == vaja);
+    }
+
+    @Test
+    public void givenSingleElementArray_whenOffset0Size2_thenSingleElement() throws Exception {
+        final FoldingHash hasher = new FoldingHash();
+        final int[] value = hasher.extract(new int[] { 5 }, 0, 2);
+        assertArrayEquals(new int[] { 5 }, value);
+    }
+
+    @Test
+    public void givenFiveElementArray_whenOffset0Size3_thenFirstThreeElements() throws Exception {
+        final FoldingHash hasher = new FoldingHash();
+        final int[] value = hasher.extract(new int[] { 1, 2, 3, 4, 5 }, 0, 3);
+        assertArrayEquals(new int[] { 1, 2, 3 }, value);
+    }
+
+    @Test
+    public void givenFiveElementArray_whenOffset1Size2_thenTwoElements() throws Exception {
+        final FoldingHash hasher = new FoldingHash();
+        final int[] value = hasher.extract(new int[] { 1, 2, 3, 4, 5 }, 1, 2);
+        assertArrayEquals(new int[] { 2, 3 }, value);
+    }
+
+    @Test
+    public void givenFiveElementArray_whenOffset2SizeTooBig_thenElementsToTheEnd() throws Exception {
+        final FoldingHash hasher = new FoldingHash();
+        final int[] value = hasher.extract(new int[] { 1, 2, 3, 4, 5 }, 2, 2000);
+        assertArrayEquals(new int[] { 3, 4, 5 }, value);
+    }
+
+}

autovalue/pom.xml

@@ -29,6 +29,12 @@
                 </exclusion>
             </exclusions>
         </dependency>
+        <dependency>
+            <groupId>com.google.auto.service</groupId>
+            <artifactId>auto-service</artifactId>
+            <version>${auto-service.version}</version>
+            <optional>true</optional>
+        </dependency>
 
         <dependency>
             <groupId>com.google.inject</groupId>
@@ -40,6 +46,7 @@
     <properties>
         <auto-value.version>1.3</auto-value.version>
         <auto-factory.version>1.0-beta5</auto-factory.version>
+        <auto-service.version>1.0-rc5</auto-service.version>
         <guice.version>4.2.0</guice.version>
     </properties>
 

autovalue/src/main/java/com/baeldung/autoservice/BingTranslationServiceProvider.java

@@ -0,0 +1,14 @@
+package com.baeldung.autoservice;
+
+import com.google.auto.service.AutoService;
+
+import java.util.Locale;
+
+@AutoService(TranslationService.class)
+public class BingTranslationServiceProvider implements TranslationService {
+    @Override
+    public String translate(String message, Locale from, Locale to) {
+        // implementation details
+        return message + " (translated by Bing)"; 
+    }
+}

autovalue/src/main/java/com/baeldung/autoservice/GoogleTranslationServiceProvider.java

@@ -0,0 +1,14 @@
+package com.baeldung.autoservice;
+
+import com.google.auto.service.AutoService;
+
+import java.util.Locale;
+
+@AutoService(TranslationService.class)
+public class GoogleTranslationServiceProvider implements TranslationService {
+    @Override
+    public String translate(String message, Locale from, Locale to) {
+        // implementation details
+        return message + " (translated by Google)"; 
+    }
+}

autovalue/src/main/java/com/baeldung/autoservice/TranslationService.java

@@ -0,0 +1,7 @@
+package com.baeldung.autoservice;
+
+import java.util.Locale;
+
+public interface TranslationService {
+    String translate(String message, Locale from, Locale to);
+}

autovalue/src/test/java/com/baeldung/autoservice/TranslationServiceUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.autoservice;
+
+import com.baeldung.autoservice.TranslationService;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ServiceLoader;
+import java.util.stream.StreamSupport;
+
+import static org.junit.Assert.assertEquals;
+
+public class TranslationServiceUnitTest {
+
+    private ServiceLoader<TranslationService> loader;
+
+    @Before
+    public void setUp() {
+        loader = ServiceLoader.load(TranslationService.class);
+    }
+
+    @Test
+    public void whenServiceLoaderLoads_thenLoadsAllProviders() {
+        long count = StreamSupport.stream(loader.spliterator(), false).count();
+        assertEquals(2, count);
+    }
+
+    @Test
+    public void whenServiceLoaderLoadsGoogleService_thenGoogleIsLoaded() {
+        TranslationService googleService = StreamSupport.stream(loader.spliterator(), false)
+          .filter(p -> p.getClass().getSimpleName().equals("GoogleTranslationServiceProvider"))
+          .findFirst()
+          .get();
+		
+        String message = "message";
+        assertEquals(message + " (translated by Google)", googleService.translate(message, null, null));
+    }
+}

core-java-modules/core-java-8-2/src/main/java/com/baeldung/stream/SkipLimitComparison.java

@@ -0,0 +1,46 @@
+package com.baeldung.stream;
+
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class SkipLimitComparison {
+
+    public static void main(String[] args) {
+        skipExample();
+        limitExample();
+        limitInfiniteStreamExample();
+        getEvenNumbers(10, 10).stream()
+            .forEach(System.out::println);
+    }
+
+    public static void skipExample() {
+        Stream.of(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
+            .filter(i -> i % 2 == 0)
+            .skip(2)
+            .forEach(i -> System.out.print(i + " "));
+    }
+
+    public static void limitExample() {
+        Stream.of(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
+            .filter(i -> i % 2 == 0)
+            .limit(2)
+            .forEach(i -> System.out.print(i + " "));
+    }
+
+    public static void limitInfiniteStreamExample() {
+        Stream.iterate(0, i -> i + 1)
+            .filter(i -> i % 2 == 0)
+            .limit(10)
+            .forEach(System.out::println);
+    }
+
+    private static List<Integer> getEvenNumbers(int offset, int limit) {
+        return Stream.iterate(0, i -> i + 1)
+            .filter(i -> i % 2 == 0)
+            .skip(offset)
+            .limit(limit)
+            .collect(Collectors.toList());
+    }
+
+}

core-java-modules/core-java-8/src/main/java/com/baeldung/forEach/ReverseList.java

@@ -0,0 +1,84 @@
+package com.baeldung.forEach;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+import java.util.function.Consumer;
+
+class ReverseList extends ArrayList<String> {
+
+    List<String> list = Arrays.asList("A", "B", "C", "D");
+
+    Consumer<String> removeElement = s -> {
+        System.out.println(s + " " + list.size());
+        if (s != null && s.equals("A")) {
+            list.remove("D");
+        }
+    };
+
+    @Override
+    public Iterator<String> iterator() {
+
+        final int startIndex = this.size() - 1;
+        final List<String> list = this;
+        return new Iterator<String>() {
+
+            int currentIndex = startIndex;
+
+            @Override
+            public boolean hasNext() {
+                return currentIndex >= 0;
+            }
+
+            @Override
+            public String next() {
+                String next = list.get(currentIndex);
+                currentIndex--;
+                return next;
+            }
+
+            @Override
+            public void remove() {
+                throw new UnsupportedOperationException();
+            }
+        };
+    }
+
+    public void forEach(Consumer<? super String> action) {
+        for (String s : this) {
+            action.accept(s);
+        }
+    }
+
+    public void iterateParallel() {
+        list.forEach(System.out::print);
+        System.out.print(" ");
+        list.parallelStream().forEach(System.out::print);
+    }
+
+    public void iterateReverse() {
+        List<String> myList = new ReverseList();
+        myList.addAll(list);
+        myList.forEach(System.out::print);
+        System.out.print(" ");
+        myList.stream().forEach(System.out::print);
+    }
+
+    public void removeInCollectionForEach() {
+        list.forEach(removeElement);
+    }
+
+    public void removeInStreamForEach() {
+        list.stream().forEach(removeElement);
+    }
+
+    public static void main(String[] argv) {
+
+        ReverseList collectionForEach = new ReverseList();
+        collectionForEach.iterateParallel();
+        collectionForEach.iterateReverse();
+        collectionForEach.removeInCollectionForEach();
+        collectionForEach.removeInStreamForEach();
+    }
+}

core-java-modules/core-java-exceptions/pom.xml

@@ -1,26 +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>
-    <groupId>com.baeldung.exception.numberformat</groupId>
-    <artifactId>core-java-exceptions</artifactId>
-    <version>0.0.1-SNAPSHOT</version>
-    <name>core-java-exceptions</name>
+	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.exception.numberformat</groupId>
+	<artifactId>core-java-exceptions</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<name>core-java-exceptions</name>
 
-    <parent>
-        <groupId>com.baeldung</groupId>
-        <artifactId>parent-java</artifactId>
-        <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
-    </parent>
+	<parent>
+		<groupId>com.baeldung</groupId>
+		<artifactId>parent-java</artifactId>
+		<version>0.0.1-SNAPSHOT</version>
+		<relativePath>../../parent-java</relativePath>
+	</parent>
 
-    <dependencies>
-        <dependency>
-            <groupId>junit</groupId>
-            <artifactId>junit</artifactId>
-            <version>4.12</version>
-            <scope>test</scope>
-        </dependency>
-    </dependencies>
+	<properties>
+		<commons-lang3.version>3.9</commons-lang3.version>
+	</properties>
+
+	<dependencies>
+		<dependency>
+			<groupId>junit</groupId>
+			<artifactId>junit</artifactId>
+			<version>4.12</version>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.commons</groupId>
+			<artifactId>commons-lang3</artifactId>
+			<version>${commons-lang3.version}</version>
+		</dependency>
+	</dependencies>
 
 </project>

core-java-modules/core-java-exceptions/src/test/java/com/baeldung/exception/error/ErrorGeneratorUnitTest.java

@@ -1,7 +1,6 @@
-package com.baeldung.error;
+package com.baeldung.exception.error;
 
 import org.junit.Assert;
-import org.junit.Before;
 import org.junit.Test;
 
 public class ErrorGeneratorUnitTest {

core-java-modules/core-java-lambdas/README.MD

@@ -1,3 +0,0 @@
-### Relevant Articles
-
-- [Why Do Local Variables Used in Lambdas Have to Be Final or Effectively Final?](https://www.baeldung.com/java-lambda-effectively-final-local-variables)

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

@@ -1,3 +0,0 @@
-## Relevant articles:
-
-- [Why Do Local Variables Used in Lambdas Have to Be Final or Effectively Final?](https://www.baeldung.com/java-lambda-effectively-final-local-variables)

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/rawtype/RawTypeDemo.java

@@ -0,0 +1,25 @@
+package com.baeldung.rawtype;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class RawTypeDemo {
+
+	public static void main(String[] args) {
+		RawTypeDemo rawTypeDemo = new RawTypeDemo();
+		rawTypeDemo.methodA();
+	}
+
+	public void methodA() {
+		// parameterized type
+		List<String> listStr = new ArrayList<>();
+		listStr.add("Hello Folks!");
+		methodB(listStr);
+		String s = listStr.get(1); // ClassCastException at run time
+	}
+
+	public void methodB(List rawList) { // Inexpressive raw type
+		rawList.add(1); // Unsafe operation
+	}
+
+}

java-collections-conversions/src/test/java/com/baeldung/convertiteratortolist/ConvertIteratorToListServiceUnitTest.java

@@ -0,0 +1,100 @@
+package com.baeldung.convertiteratortolist;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.collection.IsCollectionWithSize.hasSize;
+import static org.hamcrest.collection.IsIterableContainingInAnyOrder.containsInAnyOrder;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+import org.apache.commons.collections4.IteratorUtils;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Lists;
+
+public class ConvertIteratorToListServiceUnitTest {
+
+    Iterator<Integer> iterator;
+
+    @Before
+    public void setUp() throws Exception {
+        iterator = Arrays.asList(1, 2, 3)
+            .iterator();
+    }
+
+    @Test
+    public void givenAnIterator_whenConvertIteratorToListUsingWhileLoop_thenReturnAList() {
+
+        List<Integer> actualList = new ArrayList<Integer>();
+
+        // Convert Iterator to List using while loop dsf
+        while (iterator.hasNext()) {
+            actualList.add(iterator.next());
+        }
+
+        assertThat(actualList, hasSize(3));
+        assertThat(actualList, containsInAnyOrder(1, 2, 3));
+    }
+
+    @Test
+    public void givenAnIterator_whenConvertIteratorToListAfterJava8_thenReturnAList() {
+        List<Integer> actualList = new ArrayList<Integer>();
+
+        // Convert Iterator to List using Java 8
+        iterator.forEachRemaining(actualList::add);
+
+        assertThat(actualList, hasSize(3));
+        assertThat(actualList, containsInAnyOrder(1, 2, 3));
+    }
+
+    @Test
+    public void givenAnIterator_whenConvertIteratorToListJava8Stream_thenReturnAList() {
+
+        // Convert iterator to iterable
+        Iterable<Integer> iterable = () -> iterator;
+
+        // Extract List from stream
+        List<Integer> actualList = StreamSupport
+            .stream(iterable.spliterator(), false)
+            .collect(Collectors.toList());
+
+        assertThat(actualList, hasSize(3));
+        assertThat(actualList, containsInAnyOrder(1, 2, 3));
+    }
+
+    @Test
+    public void givenAnIterator_whenConvertIteratorToImmutableListWithGuava_thenReturnAList() {
+
+        // Convert Iterator to an Immutable list using Guava library in Java
+        List<Integer> actualList = ImmutableList.copyOf(iterator);
+
+        assertThat(actualList, hasSize(3));
+        assertThat(actualList, containsInAnyOrder(1, 2, 3));
+    }
+
+    @Test
+    public void givenAnIterator_whenConvertIteratorToMutableListWithGuava_thenReturnAList() {
+
+        // Convert Iterator to a mutable list using Guava library in Java
+        List<Integer> actualList = Lists.newArrayList(iterator);
+
+        assertThat(actualList, hasSize(3));
+        assertThat(actualList, containsInAnyOrder(1, 2, 3));
+    }
+
+    @Test
+    public void givenAnIterator_whenConvertIteratorToMutableListWithApacheCommons_thenReturnAList() {
+
+        // Convert Iterator to a mutable list using Apache Commons library in Java
+        List<Integer> actualList = IteratorUtils.toList(iterator);
+
+        assertThat(actualList, hasSize(3));
+        assertThat(actualList, containsInAnyOrder(1, 2, 3));
+    }
+}

java-collections-conversions/src/test/java/org/baeldung/java/collections/IterableToCollectionUnitTest.java

@@ -0,0 +1,122 @@
+package org.baeldung.java.collections;
+
+import static org.hamcrest.Matchers.contains;
+import static org.junit.Assert.assertThat;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+import org.apache.commons.collections4.IterableUtils;
+import org.apache.commons.collections4.IteratorUtils;
+import org.junit.Test;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Lists;
+
+public class IterableToCollectionUnitTest {
+
+    Iterable<String> iterable = Arrays.asList("john", "tom", "jane");
+    Iterator<String> iterator = iterable.iterator();
+
+    @Test
+    public void whenConvertIterableToListUsingJava_thenSuccess() {
+        List<String> result = new ArrayList<String>();
+        for (String str : iterable) {
+            result.add(str);
+        }
+
+        assertThat(result, contains("john", "tom", "jane"));
+    }
+
+    @Test
+    public void whenConvertIterableToListUsingJava8_thenSuccess() {
+        List<String> result = new ArrayList<String>();
+        iterable.forEach(result::add);
+
+        assertThat(result, contains("john", "tom", "jane"));
+    }
+
+    @Test
+    public void whenConvertIterableToListUsingJava8WithSpliterator_thenSuccess() {
+        List<String> result = StreamSupport.stream(iterable.spliterator(), false)
+            .collect(Collectors.toList());
+
+        assertThat(result, contains("john", "tom", "jane"));
+    }
+
+    @Test
+    public void whenConvertIterableToListUsingGuava_thenSuccess() {
+        List<String> result = Lists.newArrayList(iterable);
+
+        assertThat(result, contains("john", "tom", "jane"));
+    }
+
+    @Test
+    public void whenConvertIterableToImmutableListUsingGuava_thenSuccess() {
+        List<String> result = ImmutableList.copyOf(iterable);
+
+        assertThat(result, contains("john", "tom", "jane"));
+    }
+
+    @Test
+    public void whenConvertIterableToListUsingApacheCommons_thenSuccess() {
+        List<String> result = IterableUtils.toList(iterable);
+
+        assertThat(result, contains("john", "tom", "jane"));
+    }
+
+    // ======================== Iterator
+
+    @Test
+    public void whenConvertIteratorToListUsingJava_thenSuccess() {
+        List<String> result = new ArrayList<String>();
+        while (iterator.hasNext()) {
+            result.add(iterator.next());
+        }
+
+        assertThat(result, contains("john", "tom", "jane"));
+    }
+
+    @Test
+    public void whenConvertIteratorToListUsingJava8_thenSuccess() {
+        List<String> result = new ArrayList<String>();
+        iterator.forEachRemaining(result::add);
+
+        assertThat(result, contains("john", "tom", "jane"));
+    }
+
+    @Test
+    public void whenConvertIteratorToListUsingJava8WithSpliterator_thenSuccess() {
+        List<String> result = StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, Spliterator.ORDERED), false)
+            .collect(Collectors.toList());
+
+        assertThat(result, contains("john", "tom", "jane"));
+    }
+
+    @Test
+    public void whenConvertIteratorToListUsingGuava_thenSuccess() {
+        List<String> result = Lists.newArrayList(iterator);
+
+        assertThat(result, contains("john", "tom", "jane"));
+    }
+
+    @Test
+    public void whenConvertIteratorToImmutableListUsingGuava_thenSuccess() {
+        List<String> result = ImmutableList.copyOf(iterator);
+
+        assertThat(result, contains("john", "tom", "jane"));
+    }
+
+    @Test
+    public void whenConvertIteratorToListUsingApacheCommons_thenSuccess() {
+        List<String> result = IteratorUtils.toList(iterator);
+
+        assertThat(result, contains("john", "tom", "jane"));
+    }
+}

java-streams/src/test/java/com/baeldung/intstreams/conversion/IntStreamsConversionsUnitTest.java

@@ -0,0 +1,40 @@
+package com.baeldung.intstreams.conversion;
+
+import org.junit.Test;
+
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class IntStreamsConversionsUnitTest {
+
+    @Test
+    public void intStreamToArray() {
+        int[] first50EvenNumbers = IntStream.iterate(0, i -> i + 2)
+                .limit(50)
+                .toArray();
+
+        assertThat(first50EvenNumbers).hasSize(50);
+        assertThat(first50EvenNumbers[2]).isEqualTo(4);
+    }
+
+    @Test
+    public void intStreamToList() {
+        List<Integer> first50IntegerNumbers = IntStream.range(0, 50)
+                .boxed()
+                .collect(Collectors.toList());
+
+        assertThat(first50IntegerNumbers).hasSize(50);
+        assertThat(first50IntegerNumbers.get(2)).isEqualTo(2);
+    }
+
+    @Test
+    public void intStreamToString() {
+        String first3numbers = IntStream.of(0, 1, 2)
+                .mapToObj(String::valueOf)
+                .collect(Collectors.joining(", ", "[", "]"));
+
+        assertThat(first3numbers).isEqualTo("[0, 1, 2]");
+    }
+}

libraries-2/pom.xml

@@ -50,11 +50,42 @@
 			<artifactId>picocli</artifactId>
 			<version>${picocli.version}</version>
 		</dependency>
+        <dependency>
+            <groupId>org.ejml</groupId>
+            <artifactId>ejml-all</artifactId>
+            <version>${ejml.version}</version>
+        </dependency>
+		<dependency>
+			<groupId>org.nd4j</groupId>
+			<artifactId>nd4j-native</artifactId>
+			<version>${nd4j.version}</version>
+		</dependency>
+        <dependency>
+            <groupId>org.la4j</groupId>
+            <artifactId>la4j</artifactId>
+            <version>${la4j.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>colt</groupId>
+            <artifactId>colt</artifactId>
+            <version>${colt.version}</version>
+        </dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter</artifactId>
 			<version>${spring-boot-starter.version}</version>
 		</dependency>
+		<dependency>
+			<groupId>net.openhft</groupId>
+			<artifactId>chronicle-map</artifactId>
+			<version>${chronicle.map.version}</version>
+			<exclusions>
+				<exclusion>
+					<groupId>com.sun.java</groupId>
+					<artifactId>tools</artifactId>
+				</exclusion>
+			</exclusions>
+		</dependency>
 
 		<!-- Dependencies for response decoder with okhttp -->
 		<dependency>
@@ -82,10 +113,22 @@
 			<scope>test</scope>
 		</dependency>
 
-                <dependency>
-                    <groupId>edu.uci.ics</groupId>
-                    <artifactId>crawler4j</artifactId>
-                    <version>${crawler4j.version}</version>
+        <dependency>
+            <groupId>edu.uci.ics</groupId>
+            <artifactId>crawler4j</artifactId>
+            <version>${crawler4j.version}</version>
+		</dependency>
+
+		<!-- Benchmarking -->
+		<dependency>
+			<groupId>org.openjdk.jmh</groupId>
+			<artifactId>jmh-core</artifactId>
+			<version>${jmh.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.openjdk.jmh</groupId>
+			<artifactId>jmh-generator-annprocess</artifactId>
+			<version>${jmh.version}</version>
 		</dependency>
           
 	</dependencies>
@@ -95,7 +138,13 @@
 		<classgraph.version>4.8.28</classgraph.version>
 		<jbpm.version>6.0.0.Final</jbpm.version>
 		<picocli.version>3.9.6</picocli.version>
+		<chronicle.map.version>3.17.2</chronicle.map.version>
         <crawler4j.version>4.4.0</crawler4j.version>
 		<spring-boot-starter.version>2.1.4.RELEASE</spring-boot-starter.version>
+		<ejml.version>0.38</ejml.version>
+		<nd4j.version>1.0.0-beta4</nd4j.version>
+		<colt.version>1.2.0</colt.version>
+		<la4j.version>0.6.0</la4j.version>
+		<jmh.version>1.19</jmh.version>
 	</properties>
 </project>

libraries-2/src/test/java/com/baeldung/chroniclemap/ChronicleMapUnitTest.java

@@ -0,0 +1,132 @@
+package com.baeldung.chroniclemap;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+
+import java.io.File;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import net.openhft.chronicle.core.values.LongValue;
+import net.openhft.chronicle.map.ChronicleMap;
+import net.openhft.chronicle.map.ExternalMapQueryContext;
+import net.openhft.chronicle.map.MapEntry;
+import net.openhft.chronicle.values.Values;
+
+public class ChronicleMapUnitTest {
+
+    static ChronicleMap<LongValue, CharSequence> persistedCountryMap = null;
+
+    static ChronicleMap<LongValue, CharSequence> inMemoryCountryMap = null;
+
+    static ChronicleMap<Integer, Set<Integer>> multiMap = null;
+
+    @SuppressWarnings({ "unchecked", "rawtypes" })
+    @BeforeClass
+    public static void init() {
+        try {
+            inMemoryCountryMap = ChronicleMap.of(LongValue.class, CharSequence.class)
+                .name("country-map")
+                .entries(50)
+                .averageValue("America")
+                .create();
+
+            persistedCountryMap = ChronicleMap.of(LongValue.class, CharSequence.class)
+                .name("country-map")
+                .entries(50)
+                .averageValue("America")
+                .createPersistedTo(new File(System.getProperty("user.home") + "/country-details.dat"));
+
+            Set<Integer> averageValue = IntStream.of(1, 2)
+                .boxed()
+                .collect(Collectors.toSet());
+            multiMap = ChronicleMap.of(Integer.class, (Class<Set<Integer>>) (Class) Set.class)
+                .name("multi-map")
+                .entries(50)
+                .averageValue(averageValue)
+                .create();
+
+            LongValue qatarKey = Values.newHeapInstance(LongValue.class);
+            qatarKey.setValue(1);
+            inMemoryCountryMap.put(qatarKey, "Qatar");
+
+            LongValue key = Values.newHeapInstance(LongValue.class);
+            key.setValue(1);
+            persistedCountryMap.put(key, "Romania");
+            key.setValue(2);
+            persistedCountryMap.put(key, "India");
+
+            Set<Integer> set1 = new HashSet<>();
+            set1.add(1);
+            set1.add(2);
+            multiMap.put(1, set1);
+
+            Set<Integer> set2 = new HashSet<>();
+            set2.add(3);
+            multiMap.put(2, set2);
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    @Test
+    public void givenGetQuery_whenCalled_shouldReturnResult() {
+        LongValue key = Values.newHeapInstance(LongValue.class);
+        key.setValue(1);
+        CharSequence country = inMemoryCountryMap.get(key);
+        assertThat(country.toString(), is(equalTo("Qatar")));
+    }
+
+    @Test
+    public void givenGetUsingQuery_whenCalled_shouldReturnResult() {
+        LongValue key = Values.newHeapInstance(LongValue.class);
+        StringBuilder country = new StringBuilder();
+        key.setValue(1);
+        persistedCountryMap.getUsing(key, country);
+        assertThat(country.toString(), is(equalTo("Romania")));
+        key.setValue(2);
+        persistedCountryMap.getUsing(key, country);
+        assertThat(country.toString(), is(equalTo("India")));
+    }
+
+    @Test
+    public void  givenMultipleKeyQuery_whenProcessed_shouldChangeTheValue() {
+        try (ExternalMapQueryContext<Integer, Set<Integer>, ?> fistContext = multiMap.queryContext(1)) {
+            try (ExternalMapQueryContext<Integer, Set<Integer>, ?> secondContext = multiMap.queryContext(2)) {
+                fistContext.updateLock()
+                    .lock();
+                secondContext.updateLock()
+                    .lock();
+                MapEntry<Integer, Set<Integer>> firstEntry = fistContext.entry();
+                Set<Integer> firstSet = firstEntry.value()
+                    .get();
+                firstSet.remove(2);
+                MapEntry<Integer, Set<Integer>> secondEntry = secondContext.entry();
+                Set<Integer> secondSet = secondEntry.value()
+                    .get();
+                secondSet.add(4);
+                firstEntry.doReplaceValue(fistContext.wrapValueAsData(firstSet));
+                secondEntry.doReplaceValue(secondContext.wrapValueAsData(secondSet));
+            }
+        } finally {
+            assertThat(multiMap.get(1)
+                .size(), is(equalTo(1)));
+            assertThat(multiMap.get(2)
+                .size(), is(equalTo(2)));
+        }
+    }
+
+    @AfterClass
+    public static void finish() {
+        persistedCountryMap.close();
+        inMemoryCountryMap.close();
+        multiMap.close();
+    }
+}

libraries-2/src/test/java/com/baeldung/matrices/MatrixMultiplicationBenchmarking.java

@@ -0,0 +1,9 @@
+package com.baeldung.matrices;
+
+public class MatrixMultiplicationBenchmarking {
+
+    public static void main(String[] args) throws Exception {
+        org.openjdk.jmh.Main.main(args);
+    }
+
+}

libraries-2/src/test/java/com/baeldung/matrices/apache/RealMatrixUnitTest.java

@@ -0,0 +1,47 @@
+package com.baeldung.matrices.apache;
+
+import org.apache.commons.math3.linear.Array2DRowRealMatrix;
+import org.apache.commons.math3.linear.RealMatrix;
+import org.junit.jupiter.api.Test;
+import org.openjdk.jmh.annotations.*;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@BenchmarkMode(Mode.AverageTime)
+@Fork(value = 2)
+@Warmup(iterations = 5)
+@Measurement(iterations = 10)
+public class RealMatrixUnitTest {
+
+    @Test
+    @Benchmark
+    public void givenTwoMatrices_whenMultiply_thenMultiplicatedMatrix() {
+        RealMatrix firstMatrix = new Array2DRowRealMatrix(
+          new double[][] {
+            new double[] {1d, 5d},
+            new double[] {2d, 3d},
+            new double[] {1d ,7d}
+          }
+        );
+
+        RealMatrix secondMatrix = new Array2DRowRealMatrix(
+          new double[][] {
+            new double[] {1d, 2d, 3d, 7d},
+            new double[] {5d, 2d, 8d, 1d}
+          }
+        );
+
+        RealMatrix expected = new Array2DRowRealMatrix(
+          new double[][] {
+            new double[] {26d, 12d, 43d, 12d},
+            new double[] {17d, 10d, 30d, 17d},
+            new double[] {36d, 16d, 59d, 14d}
+          }
+        );
+
+        RealMatrix actual = firstMatrix.multiply(secondMatrix);
+
+        assertThat(actual).isEqualTo(expected);
+    }
+
+}

libraries-2/src/test/java/com/baeldung/matrices/colt/DoubleMatrix2DUnitTest.java

@@ -0,0 +1,51 @@
+package com.baeldung.matrices.colt;
+
+import cern.colt.matrix.DoubleFactory2D;
+import cern.colt.matrix.DoubleMatrix2D;
+import cern.colt.matrix.linalg.Algebra;
+import org.junit.jupiter.api.Test;
+import org.openjdk.jmh.annotations.*;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@BenchmarkMode(Mode.AverageTime)
+@Fork(value = 2)
+@Warmup(iterations = 5)
+@Measurement(iterations = 10)
+public class DoubleMatrix2DUnitTest {
+
+    @Test
+    @Benchmark
+    public void givenTwoMatrices_whenMultiply_thenMultiplicatedMatrix() {
+        DoubleFactory2D doubleFactory2D = DoubleFactory2D.dense;
+
+        DoubleMatrix2D firstMatrix = doubleFactory2D.make(
+          new double[][] {
+            new double[] {1d, 5d},
+            new double[] {2d, 3d},
+            new double[] {1d ,7d}
+          }
+        );
+
+        DoubleMatrix2D secondMatrix = doubleFactory2D.make(
+          new double[][] {
+            new double[] {1d, 2d, 3d, 7d},
+            new double[] {5d, 2d, 8d, 1d}
+          }
+        );
+
+        DoubleMatrix2D expected = doubleFactory2D.make(
+          new double[][] {
+            new double[] {26d, 12d, 43d, 12d},
+            new double[] {17d, 10d, 30d, 17d},
+            new double[] {36d, 16d, 59d, 14d}
+          }
+        );
+
+        Algebra algebra = new Algebra();
+        DoubleMatrix2D actual = algebra.mult(firstMatrix, secondMatrix);
+
+        assertThat(actual).isEqualTo(expected);
+    }
+
+}

libraries-2/src/test/java/com/baeldung/matrices/ejml/SimpleMatrixUnitTest.java

@@ -0,0 +1,46 @@
+package com.baeldung.matrices.ejml;
+
+import org.ejml.simple.SimpleMatrix;
+import org.junit.jupiter.api.Test;
+import org.openjdk.jmh.annotations.*;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@BenchmarkMode(Mode.AverageTime)
+@Fork(value = 2)
+@Warmup(iterations = 5)
+@Measurement(iterations = 10)
+public class SimpleMatrixUnitTest {
+
+    @Test
+    @Benchmark
+    public void givenTwoMatrices_whenMultiply_thenMultiplicatedMatrix() {
+        SimpleMatrix firstMatrix = new SimpleMatrix(
+          new double[][] {
+            new double[] {1d, 5d},
+            new double[] {2d, 3d},
+            new double[] {1d ,7d}
+          }
+        );
+
+        SimpleMatrix secondMatrix = new SimpleMatrix(
+          new double[][] {
+            new double[] {1d, 2d, 3d, 7d},
+            new double[] {5d, 2d, 8d, 1d}
+          }
+        );
+
+        SimpleMatrix expected = new SimpleMatrix(
+          new double[][] {
+            new double[] {26d, 12d, 43d, 12d},
+            new double[] {17d, 10d, 30d, 17d},
+            new double[] {36d, 16d, 59d, 14d}
+          }
+        );
+
+        SimpleMatrix actual = firstMatrix.mult(secondMatrix);
+
+        assertThat(actual).matches(m -> m.isIdentical(expected, 0d));
+    }
+
+}