Merge branch 'master' of https://github.com/eugenp/tutorials

.gitignore

@@ -85,3 +85,9 @@ spring-soap/src/main/java/com/baeldung/springsoap/gen/
 /report-*.json
 transaction.log
 *-shell.log
+
+apache-cxf/cxf-aegis/baeldung.xml
+apache-fop/src/test/resources/input.xml
+apache-fop/src/test/resources/output_herold.pdf
+apache-fop/src/test/resources/output_html2fo.pdf
+apache-fop/src/test/resources/output_jtidy.pdf

algorithms-miscellaneous-3/README.md

@@ -16,4 +16,6 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Efficient Word Frequency Calculator in Java](https://www.baeldung.com/java-word-frequency)
 - [Interpolation Search in Java](https://www.baeldung.com/java-interpolation-search)
 - [The K-Means Clustering Algorithm in Java](https://www.baeldung.com/java-k-means-clustering-algorithm)
+- [Creating a Custom Annotation in Java](https://www.baeldung.com/java-custom-annotation)
+- [Breadth-First Search Algorithm in Java](https://www.baeldung.com/java-breadth-first-search)
 - More articles: [[<-- prev]](/algorithms-miscellaneous-2) [[next -->]](/algorithms-miscellaneous-4)

algorithms-miscellaneous-4/README.md

@@ -1,7 +1,6 @@
 ## Algorithms - Miscellaneous
 
-This module contains articles about algorithms. Some classes of algorithms, e.g., [sorting](/../algorithms-sorting) and
-[genetic algorithms](/../algorithms-genetic), have their own dedicated modules. 
+This module contains articles about algorithms. Some classes of algorithms, e.g., [sorting](https://github.com/eugenp/tutorials/blob/algorithms-sorting) and [genetic algorithms](https://github.com/eugenp/tutorials/blob/algorithms-genetic), have their own dedicated modules.
 
 ### Relevant articles:
 
@@ -12,4 +11,4 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Find Substrings That Are Palindromes in Java](https://www.baeldung.com/java-palindrome-substrings)
 - [Find the Longest Substring without Repeating Characters](https://www.baeldung.com/java-longest-substring-without-repeated-characters)
 - [Permutations of an Array in Java](https://www.baeldung.com/java-array-permutations)
-- More articles: [[<-- prev]](/../algorithms-miscellaneous-3) [[next -->]](/../algorithms-miscellaneous-5)
+- More articles: [[<-- prev]](/algorithms-miscellaneous-3) [[next -->]](/algorithms-miscellaneous-5)

algorithms-miscellaneous-5/README.md

@@ -8,4 +8,5 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Converting Between Byte Arrays and Hexadecimal Strings in Java](https://www.baeldung.com/java-byte-arrays-hex-strings)
 - [Reversing a Binary Tree in Java](https://www.baeldung.com/java-reversing-a-binary-tree)
 - [Find If Two Numbers Are Relatively Prime in Java](https://www.baeldung.com/java-two-relatively-prime-numbers)
+- [Knapsack Problem Implementation in Java](https://www.baeldung.com/java-knapsack)
 - More articles: [[<-- prev]](/../algorithms-miscellaneous-4)

algorithms-sorting/README.md

@@ -17,3 +17,4 @@ This module contains articles about sorting algorithms.
 - [Sorting Strings by Contained Numbers in Java](https://www.baeldung.com/java-sort-strings-contained-numbers)
 - [Radix Sort in Java](https://www.baeldung.com/java-radix-sort)
 - [Sorting a String Alphabetically in Java](https://www.baeldung.com/java-sort-string-alphabetically)
+- [Bucket Sort in Java](https://www.baeldung.com/java-bucket-sort)

code-generation/pom.xml

@@ -12,10 +12,16 @@
     </parent>
 
     <dependencies>
+        <dependency>
+            <groupId>com.google.auto.value</groupId>
+            <artifactId>auto-value-annotations</artifactId>
+            <version>${auto-value.version}</version>
+        </dependency>
         <dependency>
             <groupId>com.google.auto.value</groupId>
             <artifactId>auto-value</artifactId>
             <version>${auto-value.version}</version>
+            <scope>provided</scope>
         </dependency>
         <dependency>
             <groupId>com.google.auto.factory</groupId>
@@ -43,9 +49,9 @@
     </dependencies>
 
     <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>
+        <auto-value.version>1.6.6</auto-value.version>
+        <auto-factory.version>1.0-beta6</auto-factory.version>
+        <auto-service.version>1.0-rc6</auto-service.version>
         <guice.version>4.2.0</guice.version>
     </properties>
 

code-generation/src/main/java/com/baeldung/autovalue/Person.java

@@ -0,0 +1,38 @@
+package com.baeldung.autovalue;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import com.google.auto.value.AutoValue;
+
+@AutoValue
+public abstract class Person {
+
+    public abstract String name();
+
+    public abstract List<String> favoriteMovies();
+
+    public static Builder builder() {
+        return new AutoValue_Person.Builder();
+    }
+
+    @AutoValue.Builder
+    public static abstract class Builder {
+
+        public abstract Builder name(String value);
+
+        public abstract Builder favoriteMovies(List<String> value);
+
+        abstract List<String> favoriteMovies();
+
+        abstract Person autoBuild();
+
+        public Person build() {
+            List<String> favoriteMovies = favoriteMovies();
+            List<String> copy = Collections.unmodifiableList(new ArrayList<>(favoriteMovies));
+            favoriteMovies(copy);
+            return autoBuild();
+        }
+    }
+}

code-generation/src/test/java/com/baeldung/autovalue/PersonUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.autovalue;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.Test;
+
+/**
+ * Unit Test which verifies that the {@link Person} value object creates defensive copies of its favoriteMovies list.
+ */
+public class PersonUnitTest {
+
+    @Test
+    public void givenNewPerson_whenModifyOriginalList_thenValueObjectIsNotAlsoModified() {
+        // GIVEN new Person
+        List<String> originalFavoriteMoviesList = new ArrayList<String>();
+        originalFavoriteMoviesList.add("Training Day");
+        originalFavoriteMoviesList.add("Fast and the Furious");
+        Person person = Person.builder()
+            .name("Dan")
+            .favoriteMovies(originalFavoriteMoviesList)
+            .build();
+
+        // WHEN modify original list
+        originalFavoriteMoviesList.add("Friday");
+
+        // THEN Person remains unaffected
+        assertFalse(person.favoriteMovies()
+            .contains("Friday"));
+        assertEquals(2, person.favoriteMovies()
+            .size());
+    }
+
+}

core-groovy-2/README.md

@@ -12,4 +12,5 @@ This module contains articles about core Groovy concepts
 - [Concatenate Strings with Groovy](https://www.baeldung.com/groovy-concatenate-strings)
 - [Metaprogramming in Groovy](https://www.baeldung.com/groovy-metaprogramming)
 - [A Quick Guide to Working with Web Services in Groovy](https://www.baeldung.com/groovy-web-services)
+- [Categories in Groovy](https://www.baeldung.com/groovy-categories)
 - [[<-- Prev]](/core-groovy)

core-groovy-collections/README.md

@@ -5,4 +5,6 @@ This module contains articles about Groovy core collections
 ## Relevant articles:
 
 - [Maps in Groovy](https://www.baeldung.com/groovy-maps)
-
+- [Finding Elements in Collections in Groovy](https://www.baeldung.com/groovy-collections-find-elements)
+- [Lists in Groovy](https://www.baeldung.com/groovy-lists)
+- [A Quick Guide to Iterating a Map in Groovy](https://www.baeldung.com/groovy-map-iterating)

core-groovy-collections/src/test/groovy/com/baeldung/find/ListFindUnitTest.groovy

@@ -1,11 +1,11 @@
-package com.baeldung.lists
+package com.baeldung.find
 
-import com.baeldung.Person
+import com.baeldung.find.Person
 import org.junit.Test
 
 import static org.junit.Assert.*
 
-class ListUnitTest {
+class ListFindUnitTest {
 
     private final personList = [
       new Person("Regina", "Fitzpatrick", 25),

core-groovy-collections/src/test/groovy/com/baeldung/find/MapFindUnitTest.groovy

@@ -1,11 +1,11 @@
-package com.baeldung.map
+package com.baeldung.find
 
-import com.baeldung.Person
+import com.baeldung.find.Person
 import org.junit.Test
 
 import static org.junit.Assert.*
 
-class MapUnitTest {
+class MapFindUnitTest {
 
     private final personMap = [
       Regina : new Person("Regina", "Fitzpatrick", 25),
@@ -13,84 +13,6 @@ class MapUnitTest {
       Lucian : new Person("Lucian", "Walter", 30)
     ]
 
-    @Test
-    void whenUsingEach_thenMapIsIterated() {
-        def map = [
-            'FF0000' : 'Red',
-            '00FF00' : 'Lime',
-            '0000FF' : 'Blue',
-            'FFFF00' : 'Yellow'
-        ]
-
-        map.each { println "Hex Code: $it.key = Color Name: $it.value" }
-    }
-
-    @Test
-    void whenUsingEachWithEntry_thenMapIsIterated() {
-        def map = [
-            'E6E6FA' : 'Lavender',
-            'D8BFD8' : 'Thistle',
-            'DDA0DD' : 'Plum',
-        ]
-
-        map.each { entry -> println "Hex Code: $entry.key = Color Name: $entry.value" }
-    }
-
-    @Test
-    void whenUsingEachWithKeyAndValue_thenMapIsIterated() {
-        def map = [
-            '000000' : 'Black',
-            'FFFFFF' : 'White',
-            '808080' : 'Gray'
-        ]
-
-        map.each { key, val ->
-            println "Hex Code: $key = Color Name $val"
-        }
-    }
-
-    @Test
-    void whenUsingEachWithIndexAndEntry_thenMapIsIterated() {
-        def map = [
-            '800080' : 'Purple',
-            '4B0082' : 'Indigo',
-            '6A5ACD' : 'Slate Blue'
-        ]
-
-        map.eachWithIndex { entry, index ->
-            def indent = ((index == 0 || index % 2 == 0) ? "   " : "")
-            println "$indent Hex Code: $entry.key = Color Name: $entry.value"
-        }
-    }
-
-    @Test
-    void whenUsingEachWithIndexAndKeyAndValue_thenMapIsIterated() {
-        def map = [
-            'FFA07A' : 'Light Salmon',
-            'FF7F50' : 'Coral',
-            'FF6347' : 'Tomato',
-            'FF4500' : 'Orange Red'
-        ]
-
-        map.eachWithIndex { key, val, index ->
-            def indent = ((index == 0 || index % 2 == 0) ? "   " : "")
-            println "$indent Hex Code: $key = Color Name: $val"
-        }
-    }
-
-    @Test
-    void whenUsingForLoop_thenMapIsIterated() {
-        def map = [
-            '2E8B57' : 'Seagreen',
-            '228B22' : 'Forest Green',
-            '008000' : 'Green'
-        ]
-
-        for (entry in map) {
-            println "Hex Code: $entry.key = Color Name: $entry.value"
-        }
-    }
-
     @Test
     void whenMapContainsKeyElement_thenCheckReturnsTrue() {
         def map = [a: 'd', b: 'e', c: 'f']

core-groovy-collections/src/test/groovy/com/baeldung/find/Person.groovy

@@ -1,4 +1,4 @@
-package com.baeldung
+package com.baeldung.find
 
 class Person {
     private String firstname

core-groovy-collections/src/test/groovy/com/baeldung/find/SetFindUnitTest.groovy

@@ -1,10 +1,10 @@
-package com.baeldung.set
+package com.baeldung.find
 
 import org.junit.Test
 
 import static org.junit.Assert.assertTrue
 
-class SetUnitTest {
+class SetFindUnitTest {
 
     @Test
     void whenSetContainsElement_thenCheckReturnsTrue() {

core-groovy-collections/src/test/groovy/com/baeldung/iteratemap/IterateMapUnitTest.groovy

@@ -0,0 +1,87 @@
+package com.baeldung.iteratemap
+
+import com.baeldung.find.Person
+import org.junit.Test
+
+import static org.junit.Assert.*
+
+class IterateMapUnitTest {
+
+    @Test
+    void whenUsingEach_thenMapIsIterated() {
+        def map = [
+                'FF0000' : 'Red',
+                '00FF00' : 'Lime',
+                '0000FF' : 'Blue',
+                'FFFF00' : 'Yellow'
+        ]
+
+        map.each { println "Hex Code: $it.key = Color Name: $it.value" }
+    }
+
+    @Test
+    void whenUsingEachWithEntry_thenMapIsIterated() {
+        def map = [
+                'E6E6FA' : 'Lavender',
+                'D8BFD8' : 'Thistle',
+                'DDA0DD' : 'Plum',
+        ]
+
+        map.each { entry -> println "Hex Code: $entry.key = Color Name: $entry.value" }
+    }
+
+    @Test
+    void whenUsingEachWithKeyAndValue_thenMapIsIterated() {
+        def map = [
+                '000000' : 'Black',
+                'FFFFFF' : 'White',
+                '808080' : 'Gray'
+        ]
+
+        map.each { key, val ->
+            println "Hex Code: $key = Color Name $val"
+        }
+    }
+
+    @Test
+    void whenUsingEachWithIndexAndEntry_thenMapIsIterated() {
+        def map = [
+                '800080' : 'Purple',
+                '4B0082' : 'Indigo',
+                '6A5ACD' : 'Slate Blue'
+        ]
+
+        map.eachWithIndex { entry, index ->
+            def indent = ((index == 0 || index % 2 == 0) ? "   " : "")
+            println "$indent Hex Code: $entry.key = Color Name: $entry.value"
+        }
+    }
+
+    @Test
+    void whenUsingEachWithIndexAndKeyAndValue_thenMapIsIterated() {
+        def map = [
+                'FFA07A' : 'Light Salmon',
+                'FF7F50' : 'Coral',
+                'FF6347' : 'Tomato',
+                'FF4500' : 'Orange Red'
+        ]
+
+        map.eachWithIndex { key, val, index ->
+            def indent = ((index == 0 || index % 2 == 0) ? "   " : "")
+            println "$indent Hex Code: $key = Color Name: $val"
+        }
+    }
+
+    @Test
+    void whenUsingForLoop_thenMapIsIterated() {
+        def map = [
+                '2E8B57' : 'Seagreen',
+                '228B22' : 'Forest Green',
+                '008000' : 'Green'
+        ]
+
+        for (entry in map) {
+            println "Hex Code: $entry.key = Color Name: $entry.value"
+        }
+    }
+}

core-groovy-collections/src/test/groovy/com/baeldung/lists/ListUnitTest.groovy

@@ -1,9 +1,9 @@
-package com.baeldung.groovy.lists
+package com.baeldung.lists
 
 import static groovy.test.GroovyAssert.*
 import org.junit.Test
 
-class ListTest{
+class ListUnitTest {
 
     @Test
     void testCreateList() {

core-groovy-collections/src/test/groovy/com/baeldung/maps/MapTest.groovy

@@ -1,4 +1,4 @@
-package com.baeldung.map;
+package com.baeldung.maps;
 
 import static groovy.test.GroovyAssert.*
 import org.junit.Test

core-groovy/README.md

@@ -8,11 +8,8 @@ This module contains articles about core Groovy concepts
 - [Working with JSON in Groovy](https://www.baeldung.com/groovy-json)
 - [Reading a File in Groovy](https://www.baeldung.com/groovy-file-read)
 - [Types of Strings in Groovy](https://www.baeldung.com/groovy-strings)
-- [A Quick Guide to Iterating a Map in Groovy](https://www.baeldung.com/groovy-map-iterating)
 - [An Introduction to Traits in Groovy](https://www.baeldung.com/groovy-traits)
 - [Closures in Groovy](https://www.baeldung.com/groovy-closures)
-- [Finding Elements in Collections in Groovy](https://www.baeldung.com/groovy-collections-find-elements)
-- [Lists in Groovy](https://www.baeldung.com/groovy-lists)
 - [Converting a String to a Date in Groovy](https://www.baeldung.com/groovy-string-to-date)
 - [Guide to I/O in Groovy](https://www.baeldung.com/groovy-io)
 - [[More -->]](/core-groovy-2)

core-groovy/src/test/groovy/com/baeldung/map/MapTest.groovy

@@ -1,148 +0,0 @@
-package com.baeldung.groovy.map;
-
-import static groovy.test.GroovyAssert.*
-import org.junit.Test
-
-class MapTest{
-
-    @Test
-    void createMap() {
-
-        def emptyMap = [:]
-        assertNotNull(emptyMap)
-
-        assertTrue(emptyMap instanceof java.util.LinkedHashMap)
-
-        def map = [name:"Jerry", age: 42, city: "New York"]
-        assertTrue(map.size() == 3)
-    }
-
-    @Test
-    void addItemsToMap() {
-
-        def map = [name:"Jerry"]
-
-        map["age"] = 42
-
-        map.city = "New York"
-
-        def hobbyLiteral = "hobby"
-        def hobbyMap = [(hobbyLiteral): "Singing"]
-        map.putAll(hobbyMap)
-
-        assertTrue(map == [name:"Jerry", age: 42, city: "New York", hobby:"Singing"])
-        assertTrue(hobbyMap.hobby == "Singing")
-        assertTrue(hobbyMap[hobbyLiteral] == "Singing")
-        
-        map.plus([1:20]) // returns new map
-
-        map << [2:30]
-
-    }
-
-    @Test
-    void getItemsFromMap() {
-
-        def map = [name:"Jerry", age: 42, city: "New York", hobby:"Singing"]
-
-        assertTrue(map["name"] == "Jerry")
-
-        assertTrue(map.name == "Jerry")
-
-        def propertyAge = "age"
-        assertTrue(map[propertyAge] == 42)
-    }
-
-    @Test
-    void removeItemsFromMap() {
-
-        def map = [1:20, a:30, 2:42, 4:34, ba:67, 6:39, 7:49]
-
-        def minusMap = map.minus([2:42, 4:34]);
-        assertTrue(minusMap == [1:20, a:30, ba:67, 6:39, 7:49])
-
-        minusMap.removeAll{it -> it.key instanceof String}
-        assertTrue( minusMap == [ 1:20, 6:39, 7:49])
-
-        minusMap.retainAll{it -> it.value %2 == 0}
-        assertTrue( minusMap == [1:20])
-    }
-
-    @Test
-    void iteratingOnMaps(){
-        def map = [name:"Jerry", age: 42, city: "New York", hobby:"Singing"]
-
-        map.each{ entry -> println "$entry.key: $entry.value" }
-
-        map.eachWithIndex{ entry, i -> println "$i $entry.key: $entry.value" }
-
-        map.eachWithIndex{ key, value, i -> println "$i $key: $value" }
-    }
-
-    @Test
-    void filteringAndSearchingMaps(){
-        def map = [name:"Jerry", age: 42, city: "New York", hobby:"Singing"]
-
-        assertTrue(map.find{ it.value == "New York"}.key == "city")
-
-        assertTrue(map.findAll{ it.value == "New York"} == [city : "New York"])
-
-        map.grep{it.value == "New York"}.each{ it -> assertTrue(it.key == "city" && it.value == "New York")}
-
-        assertTrue(map.every{it -> it.value instanceof String} == false)
-
-        assertTrue(map.any{it -> it.value instanceof String} == true)
-    }
-
-    @Test
-    void collect(){
-
-        def map = [1: [name:"Jerry", age: 42, city: "New York"],
-            2: [name:"Long", age: 25, city: "New York"],
-            3: [name:"Dustin", age: 29, city: "New York"],
-            4: [name:"Dustin", age: 34, city: "New York"]]
-
-        def names = map.collect{entry -> entry.value.name} // returns only list
-        assertTrue(names == ["Jerry", "Long", "Dustin", "Dustin"])
-
-        def uniqueNames = map.collect([] as HashSet){entry -> entry.value.name}
-        assertTrue(uniqueNames == ["Jerry", "Long", "Dustin"] as Set)
-
-        def idNames = map.collectEntries{key, value -> [key, value.name]}
-        assertTrue(idNames == [1:"Jerry", 2: "Long", 3:"Dustin", 4: "Dustin"])
-
-        def below30Names = map.findAll{it.value.age < 30}.collect{key, value -> value.name}
-        assertTrue(below30Names == ["Long", "Dustin"])
-
-
-    }
-
-    @Test
-    void group(){
-        def map = [1:20, 2: 40, 3: 11, 4: 93]
-
-        def subMap = map.groupBy{it.value % 2}
-        println subMap
-        assertTrue(subMap == [0:[1:20, 2:40 ], 1:[3:11, 4:93]])
-
-        def keySubMap = map.subMap([1, 2])
-        assertTrue(keySubMap == [1:20, 2:40])
-
-    }
-
-    @Test
-    void sorting(){
-        def map = [ab:20, a: 40, cb: 11, ba: 93]
-
-        def naturallyOrderedMap = map.sort()
-        assertTrue([a:40, ab:20, ba:93, cb:11] == naturallyOrderedMap)
-
-        def compSortedMap = map.sort({ k1, k2 -> k1 <=> k2 } as Comparator)
-        assertTrue([a:40, ab:20, ba:93, cb:11] == compSortedMap)
-
-        def cloSortedMap = map.sort({ it1, it2 -> it1.value <=> it1.value })
-        assertTrue([cb:11, ab:20, a:40, ba:93] == cloSortedMap)
-
-    }
-
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/java_8_features/groupingby/Tuple.java

@@ -1,12 +1,12 @@
 package com.baeldung.java_8_features.groupingby;
 
-public class Tuple {
+import java.util.Objects;
 
-    private BlogPostType type;
-    private String author;
+public class Tuple {
+    private final BlogPostType type;
+    private final String author;
 
     public Tuple(BlogPostType type, String author) {
-        super();
         this.type = type;
         this.author = author;
     }
@@ -15,20 +15,27 @@ public class Tuple {
         return type;
     }
 
-    public void setType(BlogPostType type) {
-        this.type = type;
-    }
-
     public String getAuthor() {
         return author;
     }
 
-    public void setAuthor(String author) {
-        this.author = author;
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
+        Tuple tuple = (Tuple) o;
+        return type == tuple.type && author.equals(tuple.author);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(type, author);
     }
 
     @Override
     public String toString() {
-        return "Tuple [type=" + type + ", author=" + author + ", getType()=" + getType() + ", getAuthor()=" + getAuthor() + ", getClass()=" + getClass() + ", hashCode()=" + hashCode() + ", toString()=" + super.toString() + "]";
+        return "Tuple{" + "type=" + type + ", author='" + author + '\'' + '}';
     }
 }

core-java-modules/core-java-8/src/test/java/com/baeldung/java_8_features/groupingby/Java8GroupingByCollectorUnitTest.java

@@ -1,15 +1,32 @@
 package com.baeldung.java_8_features.groupingby;
 
-import com.baeldung.java_8_features.groupingby.BlogPost;
-import com.baeldung.java_8_features.groupingby.BlogPostType;
-import org.junit.Test;
+import static java.util.Comparator.comparingInt;
+import static java.util.stream.Collectors.averagingInt;
+import static java.util.stream.Collectors.counting;
+import static java.util.stream.Collectors.groupingBy;
+import static java.util.stream.Collectors.groupingByConcurrent;
+import static java.util.stream.Collectors.joining;
+import static java.util.stream.Collectors.mapping;
+import static java.util.stream.Collectors.maxBy;
+import static java.util.stream.Collectors.summarizingInt;
+import static java.util.stream.Collectors.summingInt;
+import static java.util.stream.Collectors.toList;
+import static java.util.stream.Collectors.toSet;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
 
-import java.util.*;
+import java.util.Arrays;
+import java.util.EnumMap;
+import java.util.IntSummaryStatistics;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
 import java.util.concurrent.ConcurrentMap;
 
-import static java.util.Comparator.comparingInt;
-import static java.util.stream.Collectors.*;
-import static org.junit.Assert.*;
+import org.junit.Test;
 
 public class Java8GroupingByCollectorUnitTest {
 
@@ -180,4 +197,19 @@ public class Java8GroupingByCollectorUnitTest {
         assertEquals(15, newsLikeStatistics.getMin());
     }
 
+    @Test
+    public void givenAListOfPosts_whenGroupedByComplexMapKeyType_thenGetAMapBetweenTupleAndList() {
+        Map<Tuple, List<BlogPost>> postsPerTypeAndAuthor = posts.stream()
+            .collect(groupingBy(post -> new Tuple(post.getType(), post.getAuthor())));
+
+        List<BlogPost> result = postsPerTypeAndAuthor.get(new Tuple(BlogPostType.GUIDE, "Author 1"));
+
+        assertThat(result.size()).isEqualTo(1);
+
+        BlogPost blogPost = result.get(0);
+
+        assertThat(blogPost.getTitle()).isEqualTo("Programming guide");
+        assertThat(blogPost.getType()).isEqualTo(BlogPostType.GUIDE);
+        assertThat(blogPost.getAuthor()).isEqualTo("Author 1");
+    }
 }

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

@@ -0,0 +1,6 @@
+## Core Java 9 streams
+
+This module contains articles about Java 9 streams
+
+### Relevant Articles: 
+- [How to Break from Java Stream forEach](https://www.baeldung.com/java-break-stream-foreach)

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

@@ -0,0 +1,31 @@
+<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-streams</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-9-streams</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>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-9-streams</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+    </properties>
+</project>

core-java-modules/core-java-9-streams/src/main/java/com/baeldung/streams/breakforeach/CustomForEach.java

@@ -1,4 +1,4 @@
-package com.baeldung.breakforeach;
+package com.baeldung.streams.breakforeach;
 
 import java.util.Spliterator;
 import java.util.function.BiConsumer;

core-java-modules/core-java-9-streams/src/main/java/com/baeldung/streams/breakforeach/CustomSpliterator.java

@@ -1,4 +1,4 @@
-package com.baeldung.breakforeach;
+package com.baeldung.streams.breakforeach;
 
 import java.util.Spliterator;
 import java.util.Spliterators;

core-java-modules/core-java-9-streams/src/main/java/com/baeldung/streams/breakforeach/CustomTakeWhile.java

@@ -1,4 +1,4 @@
-package com.baeldung.breakforeach;
+package com.baeldung.streams.breakforeach;
 
 import java.util.function.Predicate;
 import java.util.stream.Stream;

core-java-modules/core-java-9-streams/src/main/java/com/baeldung/streams/breakforeach/TakeWhileExample.java

@@ -1,4 +1,4 @@
-package com.baeldung.breakforeach;
+package com.baeldung.streams.breakforeach;
 
 import java.util.List;
 import java.util.stream.Stream;

core-java-modules/core-java-9-streams/src/test/java/com/baeldung/streams/breakforeach/BreakFromStreamForEachUnitTest.java

@@ -1,4 +1,4 @@
-package com.baeldung.breakforeach;
+package com.baeldung.streams.breakforeach;
 
 import org.junit.Test;
 

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

@@ -9,3 +9,4 @@
 - [Java @Deprecated Annotation](https://www.baeldung.com/java-deprecated)
 - [Overview of Java Built-in Annotations](https://www.baeldung.com/java-default-annotations)
 - [Creating a Custom Annotation in Java](https://www.baeldung.com/java-custom-annotation)
+- [Efficient Word Frequency Calculator in Java](https://www.baeldung.com/java-word-frequency)

core-java-modules/core-java-arrays-2/README.md

@@ -12,4 +12,5 @@ This module contains articles about Java arrays
 - [Intersection Between two Integer Arrays](https://www.baeldung.com/java-array-intersection)
 - [Removing an Element from an Array in Java](https://www.baeldung.com/java-array-remove-element)
 - [Removing the First Element of an Array](https://www.baeldung.com/java-array-remove-first-element)
+- [Adding an Element to a Java Array vs an ArrayList](https://www.baeldung.com/java-add-element-to-array-vs-list)
 - [[<-- Prev]](/core-java-modules/core-java-arrays)

core-java-modules/core-java-collections-2/README.md

@@ -12,4 +12,4 @@
 - [Sorting in Java](https://www.baeldung.com/java-sorting)
 - [Getting the Size of an Iterable in Java](https://www.baeldung.com/java-iterable-size)
 - [Java Null-Safe Streams from Collections](https://www.baeldung.com/java-null-safe-streams-from-collections)
-
+- [Operating on and Removing an Item from Stream](https://www.baeldung.com/java-use-remove-item-stream)

core-java-modules/core-java-collections-list-2/README.md

@@ -11,4 +11,5 @@ This module contains articles about the Java List collection
 - [Ways to Iterate Over a List in Java](https://www.baeldung.com/java-iterate-list)
 - [Flattening Nested Collections in Java](http://www.baeldung.com/java-flatten-nested-collections)
 - [Intersection of Two Lists in Java](https://www.baeldung.com/java-lists-intersection)
+- [Searching for a String in an ArrayList](https://www.baeldung.com/java-search-string-arraylist)
 - [[<-- Prev]](/core-java-modules/core-java-collections-list)[[Next -->]](/core-java-modules/core-java-collections-list-3)

core-java-modules/core-java-collections-list-3/src/main/java/com/baeldung/list/DuplicatesCounter.java

@@ -0,0 +1,42 @@
+package com.baeldung.list;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+/**
+ * Demo different approaches to get count of duplicated elements in an
+ * arrayList
+ */
+public class DuplicatesCounter {
+
+    public static <T> Map<T, Long> countByClassicalLoop(List<T> inputList) {
+        Map<T, Long> resultMap = new HashMap<>();
+        for (T element : inputList) {
+            if (resultMap.containsKey(element)) {
+                resultMap.put(element, resultMap.get(element) + 1L);
+            } else {
+                resultMap.put(element, 1L);
+            }
+        }
+        return resultMap;
+    }
+
+    public static <T> Map<T, Long> countByClassicalLoopWithMapCompute(List<T> inputList) {
+        Map<T, Long> resultMap = new HashMap<>();
+        for (T element : inputList) {
+            resultMap.compute(element, (k, v) -> v == null ? 1 : v + 1);
+        }
+        return resultMap;
+    }
+
+    public static <T> Map<T, Long> countByStreamToMap(List<T> inputList) {
+        return inputList.stream().collect(Collectors.toMap(Function.identity(), v -> 1L, Long::sum));
+    }
+
+    public static <T> Map<T, Long> countByStreamGroupBy(List<T> inputList) {
+        return inputList.stream().collect(Collectors.groupingBy(k -> k, Collectors.counting()));
+    }
+}

core-java-modules/core-java-collections-list-3/src/test/java/com/baeldung/list/DuplicatesCounterUnitTest.java

@@ -0,0 +1,55 @@
+package com.baeldung.list;
+
+import org.assertj.core.util.Lists;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.data.MapEntry.entry;
+
+class DuplicatesCounterUnitTest {
+
+
+    private static List<String> INPUT_LIST = Lists.list(
+        "expect1",
+        "expect2", "expect2",
+        "expect3", "expect3", "expect3",
+        "expect4", "expect4", "expect4", "expect4");
+
+    @Test
+    void givenInput_whenCountByClassicalLoop_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByClassicalLoop(INPUT_LIST);
+        verifyResult(result);
+    }
+
+
+    @Test
+    void givenInput_whenCountByClassicalLoopWithMapCompute_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByClassicalLoopWithMapCompute(INPUT_LIST);
+        verifyResult(result);
+    }
+
+    @Test
+    void givenInput_whenCountByStreamToMap_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByStreamToMap(INPUT_LIST);
+        verifyResult(result);
+    }
+
+    @Test
+    void givenInput_whenCountByStreamGroupBy_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByStreamGroupBy(INPUT_LIST);
+        verifyResult(result);
+    }
+
+    private void verifyResult(Map<String, Long> resultMap) {
+        assertThat(resultMap)
+            .isNotEmpty().hasSize(4)
+            .containsExactly(
+                entry("expect1", 1L),
+                entry("expect2", 2L),
+                entry("expect3", 3L),
+                entry("expect4", 4L));
+    }
+}

core-java-modules/core-java-datetime-computations/README.md

@@ -0,0 +1,15 @@
+## Java Date/time computations Cookbooks and Examples
+
+This module contains articles about date and time computations in Java.
+
+### Relevant Articles: 
+- [Difference Between Two Dates in Java](http://www.baeldung.com/java-date-difference)
+- [Get Date Without Time in Java](http://www.baeldung.com/java-date-without-time)
+- [How to Get All Dates Between Two Dates?](http://www.baeldung.com/java-between-dates)
+- [Extracting Year, Month and Day from Date in Java](http://www.baeldung.com/java-year-month-day)
+- [Guide to java.util.GregorianCalendar](http://www.baeldung.com/java-gregorian-calendar)
+- [Handling Daylight Savings Time in Java](http://www.baeldung.com/java-daylight-savings)
+- [Calculate Age in Java](http://www.baeldung.com/java-get-age)
+- [Increment Date in Java](http://www.baeldung.com/java-increment-date)
+- [Add Hours To a Date In Java](http://www.baeldung.com/java-add-hours-date)
+- [Introduction to Joda-Time](http://www.baeldung.com/joda-time)

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

@@ -0,0 +1,71 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-datetime-computations</artifactId>
+    <version>${project.parent.version}</version>
+    <name>core-java-datetime-computations</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>joda-time</groupId>
+            <artifactId>joda-time</artifactId>
+            <version>${joda-time.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.darwinsys</groupId>
+            <artifactId>hirondelle-date4j</artifactId>
+            <version>RELEASE</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-datetime-computations</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <joda-time.version>2.10</joda-time.version>
+        <!-- testing -->
+        <assertj.version>3.6.1</assertj.version>
+        <maven.compiler.source>1.9</maven.compiler.source>
+        <maven.compiler.target>1.9</maven.compiler.target>
+    </properties>
+</project>

core-java-modules/core-java-datetime-computations/src/test/java/com/baeldung/date/DateDiffUnitTest.java

@@ -1,6 +1,6 @@
 package com.baeldung.date;
 
-import org.junit.Test;
+import static org.junit.Assert.assertEquals;
 
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
@@ -16,7 +16,7 @@ import java.util.Locale;
 import java.util.TimeZone;
 import java.util.concurrent.TimeUnit;
 
-import static org.junit.Assert.assertEquals;
+import org.junit.Test;
 
 public class DateDiffUnitTest {
 
@@ -38,7 +38,7 @@ public class DateDiffUnitTest {
         LocalDate sixDaysBehind = now.minusDays(6);
 
         Period period = Period.between(now, sixDaysBehind);
-        int diff = period.getDays();
+        int diff = Math.abs(period.getDays());
 
         assertEquals(diff, 6);
     }
@@ -68,7 +68,8 @@ public class DateDiffUnitTest {
     public void givenTwoZonedDateTimesInJava8_whenDifferentiating_thenWeGetSix() {
         LocalDateTime ldt = LocalDateTime.now();
         ZonedDateTime now = ldt.atZone(ZoneId.of("America/Montreal"));
-        ZonedDateTime sixDaysBehind = now.withZoneSameInstant(ZoneId.of("Asia/Singapore")).minusDays(6);
+        ZonedDateTime sixDaysBehind = now.withZoneSameInstant(ZoneId.of("Asia/Singapore"))
+            .minusDays(6);
         long diff = ChronoUnit.DAYS.between(sixDaysBehind, now);
         assertEquals(diff, 6);
     }

core-java-modules/core-java-datetime-java8/README.md

@@ -0,0 +1,15 @@
+## Java 8+ Date and Time API 
+
+This module contains articles about the Date and Time API introduced with Java 8.
+
+### Relevant Articles: 
+- [Introduction to the Java 8 Date/Time API](http://www.baeldung.com/java-8-date-time-intro)
+- [Migrating to the New Java 8 Date Time API](http://www.baeldung.com/migrating-to-java-8-date-time-api)
+- [Get the Current Date, Time and Timestamp in Java 8](http://www.baeldung.com/current-date-time-and-timestamp-in-java-8)
+- [TemporalAdjuster in Java](http://www.baeldung.com/java-temporal-adjuster)
+- [ZoneOffset in Java](https://www.baeldung.com/java-zone-offset)
+- [Differences Between ZonedDateTime and OffsetDateTime](https://www.baeldung.com/java-zoneddatetime-offsetdatetime)
+- [Period and Duration in Java](http://www.baeldung.com/java-period-duration)
+- [How to Get the Start and the End of a Day using Java](http://www.baeldung.com/java-day-start-end)
+- [Set the Time Zone of a Date in Java](https://www.baeldung.com/java-set-date-time-zone)
+- [Comparing Dates in Java](https://www.baeldung.com/java-comparing-dates)

core-java-modules/core-java-datetime-java8/pom.xml

@@ -1,17 +1,16 @@
 <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>java-dates</artifactId>
-    <version>0.1.0-SNAPSHOT</version>
-    <name>java-dates</name>
+    <artifactId>core-java-datetime-java8</artifactId>
+    <version>${project.parent.version}</version>
+    <name>core-java-datetime-java8</name>
     <packaging>jar</packaging>
 
     <parent>
         <groupId>com.baeldung</groupId>
         <artifactId>parent-java</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../parent-java</relativePath>
+        <relativePath>../../parent-java</relativePath>
     </parent>
 
     <dependencies>
@@ -21,11 +20,10 @@
             <version>${commons-lang3.version}</version>
         </dependency>
         <dependency>
-            <groupId>log4j</groupId>
-            <artifactId>log4j</artifactId>
-            <version>${log4j.version}</version>
+            <groupId>joda-time</groupId>
+            <artifactId>joda-time</artifactId>
+            <version>${joda-time.version}</version>
         </dependency>
-        <!-- test scoped -->
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
@@ -33,20 +31,15 @@
             <scope>test</scope>
         </dependency>
         <dependency>
-            <groupId>joda-time</groupId>
-            <artifactId>joda-time</artifactId>
-            <version>${joda-time.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.darwinsys</groupId>
-            <artifactId>hirondelle-date4j</artifactId>
-            <version>RELEASE</version>
+            <groupId>log4j</groupId>
+            <artifactId>log4j</artifactId>
+            <version>${log4j.version}</version>
             <scope>test</scope>
         </dependency>
     </dependencies>
 
     <build>
-        <finalName>java-dates</finalName>
+        <finalName>core-java-datetime-java8</finalName>
         <resources>
             <resource>
                 <directory>src/main/resources</directory>
@@ -68,10 +61,10 @@
     </build>
 
     <properties>
+		<maven.compiler.source>1.9</maven.compiler.source>
+        <maven.compiler.target>1.9</maven.compiler.target>
         <joda-time.version>2.10</joda-time.version>
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
-		<maven.compiler.source>1.9</maven.compiler.source>
-        <maven.compiler.target>1.9</maven.compiler.target>
     </properties>
 </project>

core-java-modules/core-java-datetime-java8/src/main/java/com/baeldung/datetime/UseLocalDate.java

@@ -36,10 +36,15 @@ class UseLocalDate {
     }
 
     LocalDate getFirstDayOfMonth() {
-        LocalDate firstDayOfMonth = LocalDate.now().with(TemporalAdjusters.firstDayOfMonth());
+        LocalDate firstDayOfMonth = LocalDate.now()
+            .with(TemporalAdjusters.firstDayOfMonth());
         return firstDayOfMonth;
     }
 
+    boolean isLeapYear(LocalDate localDate) {
+        return localDate.isLeapYear();
+    }
+
     LocalDateTime getStartOfDay(LocalDate localDate) {
         LocalDateTime startofDay = localDate.atStartOfDay();
         return startofDay;

core-java-modules/core-java-datetime-java8/src/main/java/com/baeldung/datetime/UseLocalDateTime.java

@@ -2,6 +2,7 @@ package com.baeldung.datetime;
 
 import java.time.LocalDateTime;
 import java.time.LocalTime;
+import java.time.ZoneOffset;
 import java.time.temporal.ChronoField;
 
 public class UseLocalDateTime {
@@ -21,4 +22,7 @@ public class UseLocalDateTime {
         return endOfDate;
     }
 
+    LocalDateTime ofEpochSecond(int epochSecond, ZoneOffset zoneOffset) {
+        return LocalDateTime.ofEpochSecond(epochSecond, 0, zoneOffset);
+    }
 }

core-java-modules/core-java-datetime-java8/src/main/java/com/baeldung/datetime/UseLocalTime.java

@@ -9,6 +9,10 @@ public class UseLocalTime {
         return LocalTime.of(hour, min, seconds);
     }
 
+    LocalTime getLocalTimeUsingFactoryOfMethod(int hour, int min) {
+        return LocalTime.of(hour, min);
+    }
+
     LocalTime getLocalTimeUsingParseMethod(String timeRepresentation) {
         return LocalTime.parse(timeRepresentation);
     }

core-java-modules/core-java-datetime-java8/src/main/java/com/baeldung/datetime/UseZonedDateTime.java

@@ -12,31 +12,35 @@ class UseZonedDateTime {
         return ZonedDateTime.of(localDateTime, zoneId);
     }
 
+    ZonedDateTime getZonedDateTimeUsingParseMethod(String parsableString) {
+        return ZonedDateTime.parse(parsableString);
+    }
+
     ZonedDateTime getStartOfDay(LocalDate localDate, ZoneId zone) {
-        ZonedDateTime startofDay = localDate.atStartOfDay()
+        ZonedDateTime startOfDay = localDate.atStartOfDay()
             .atZone(zone);
-        return startofDay;
+        return startOfDay;
     }
 
     ZonedDateTime getStartOfDayShorthand(LocalDate localDate, ZoneId zone) {
-        ZonedDateTime startofDay = localDate.atStartOfDay(zone);
-        return startofDay;
+        ZonedDateTime startOfDay = localDate.atStartOfDay(zone);
+        return startOfDay;
     }
 
     ZonedDateTime getStartOfDayFromZonedDateTime(ZonedDateTime zonedDateTime) {
-        ZonedDateTime startofDay = zonedDateTime.toLocalDateTime()
+        ZonedDateTime startOfDay = zonedDateTime.toLocalDateTime()
             .toLocalDate()
             .atStartOfDay(zonedDateTime.getZone());
-        return startofDay;
+        return startOfDay;
     }
 
     ZonedDateTime getStartOfDayAtMinTime(ZonedDateTime zonedDateTime) {
-        ZonedDateTime startofDay = zonedDateTime.with(ChronoField.HOUR_OF_DAY, 0);
-        return startofDay;
+        ZonedDateTime startOfDay = zonedDateTime.with(ChronoField.HOUR_OF_DAY, 0);
+        return startOfDay;
     }
 
     ZonedDateTime getStartOfDayAtMidnightTime(ZonedDateTime zonedDateTime) {
-        ZonedDateTime startofDay = zonedDateTime.with(ChronoField.NANO_OF_DAY, 0);
-        return startofDay;
+        ZonedDateTime startOfDay = zonedDateTime.with(ChronoField.NANO_OF_DAY, 0);
+        return startOfDay;
     }
 }

core-java-modules/core-java-datetime-java8/src/main/java/com/baeldung/random/LegacyRandomDateTimes.java

@@ -0,0 +1,19 @@
+package com.baeldung.random;
+
+import java.util.Date;
+import java.util.concurrent.ThreadLocalRandom;
+
+public class LegacyRandomDateTimes {
+
+    public static Date between(Date startInclusive, Date endExclusive) {
+        long startMillis = startInclusive.getTime();
+        long endMillis = endExclusive.getTime();
+        long randomMillisSinceEpoch = ThreadLocalRandom.current().nextLong(startMillis, endMillis);
+
+        return new Date(randomMillisSinceEpoch);
+    }
+
+    public static Date timestamp() {
+        return new Date(ThreadLocalRandom.current().nextInt() * 1000L);
+    }
+}

core-java-modules/core-java-datetime-java8/src/main/java/com/baeldung/random/RandomDateTimes.java

@@ -0,0 +1,27 @@
+package com.baeldung.random;
+
+import java.time.Instant;
+import java.util.concurrent.ThreadLocalRandom;
+
+public class RandomDateTimes {
+
+    public static Instant timestamp() {
+        return Instant.ofEpochSecond(ThreadLocalRandom.current().nextInt());
+    }
+
+    public static Instant between(Instant startInclusive, Instant endExclusive) {
+        long startSeconds = startInclusive.getEpochSecond();
+        long endSeconds = endExclusive.getEpochSecond();
+        long random = ThreadLocalRandom.current().nextLong(startSeconds, endSeconds);
+
+        return Instant.ofEpochSecond(random);
+    }
+
+    public static Instant after(Instant startInclusive) {
+        return between(startInclusive, Instant.MAX);
+    }
+
+    public static Instant before(Instant upperExclusive) {
+        return between(Instant.MIN, upperExclusive);
+    }
+}

core-java-modules/core-java-datetime-java8/src/main/java/com/baeldung/random/RandomDates.java

@@ -0,0 +1,20 @@
+package com.baeldung.random;
+
+import java.time.LocalDate;
+import java.util.concurrent.ThreadLocalRandom;
+
+public class RandomDates {
+
+    public static LocalDate between(LocalDate startInclusive, LocalDate endExclusive) {
+        long startEpochDay = startInclusive.toEpochDay();
+        long endEpochDay = endExclusive.toEpochDay();
+        long randomDay = ThreadLocalRandom.current().nextLong(startEpochDay, endEpochDay);
+
+        return LocalDate.ofEpochDay(randomDay);
+    }
+
+    public static LocalDate date() {
+        int hundredYears = 100 * 365;
+        return LocalDate.ofEpochDay(ThreadLocalRandom.current().nextInt(-hundredYears, hundredYears));
+    }
+}

core-java-modules/core-java-datetime-java8/src/main/java/com/baeldung/random/RandomTimes.java

@@ -0,0 +1,19 @@
+package com.baeldung.random;
+
+import java.time.LocalTime;
+import java.util.concurrent.ThreadLocalRandom;
+
+public class RandomTimes {
+
+    public static LocalTime between(LocalTime startTime, LocalTime endTime) {
+        int startSeconds = startTime.toSecondOfDay();
+        int endSeconds = endTime.toSecondOfDay();
+        int randomTime = ThreadLocalRandom.current().nextInt(startSeconds, endSeconds);
+
+        return LocalTime.ofSecondOfDay(randomTime);
+    }
+
+    public static LocalTime time() {
+        return between(LocalTime.MIN, LocalTime.MAX);
+    }
+}

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/date/comparison/Java8DateTimeApiGeneralComparisonsUnitTest.java

@@ -1,12 +1,16 @@
 package com.baeldung.date.comparison;
 
-import org.junit.Test;
-
-import java.time.*;
-
 import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertThat;
 
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.LocalTime;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+
+import org.junit.Test;
+
 public class Java8DateTimeApiGeneralComparisonsUnitTest {
 
     @Test
@@ -54,10 +58,8 @@ public class Java8DateTimeApiGeneralComparisonsUnitTest {
 
     @Test
     public void givenZonedDateTimes_whenComparing_thenAssertsPass() {
-        ZonedDateTime timeInNewYork = ZonedDateTime.of(2019, 8, 10, 8, 0, 0, 0,
-          ZoneId.of("America/New_York"));
-        ZonedDateTime timeInBerlin = ZonedDateTime.of(2019, 8, 10, 14, 0, 0, 0,
-          ZoneId.of("Europe/Berlin"));
+        ZonedDateTime timeInNewYork = ZonedDateTime.of(2019, 8, 10, 8, 0, 0, 0, ZoneId.of("America/New_York"));
+        ZonedDateTime timeInBerlin = ZonedDateTime.of(2019, 8, 10, 14, 0, 0, 0, ZoneId.of("Europe/Berlin"));
 
         assertThat(timeInNewYork.isAfter(timeInBerlin), is(false));
         assertThat(timeInNewYork.isBefore(timeInBerlin), is(false));
@@ -80,4 +82,14 @@ public class Java8DateTimeApiGeneralComparisonsUnitTest {
 
         assertThat(firstTime.compareTo(secondTime), is(-1));
     }
+
+    @Test
+    public void givenMinMaxLocalTimes_whenComparing_thenAssertsPass() {
+        LocalTime minTime = LocalTime.MIN;
+        LocalTime time = LocalTime.of(8, 30);
+        LocalTime maxTime = LocalTime.MAX;
+
+        assertThat(minTime.isBefore(time), is(true));
+        assertThat(time.isBefore(maxTime), is(true));
+    }
 }

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/dateapi/JavaDurationUnitTest.java

@@ -0,0 +1,69 @@
+package com.baeldung.dateapi;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+import java.time.Duration;
+import java.time.Instant;
+import java.time.LocalTime;
+import java.time.temporal.ChronoUnit;
+
+import org.junit.Test;
+
+public class JavaDurationUnitTest {
+
+    @Test
+    public void givenATimePlus30Seconds_whenRequestingDuration_thenExpect30() {
+        LocalTime initialTime = LocalTime.of(6, 30, 0);
+        LocalTime finalTime = initialTime.plus(Duration.ofSeconds(30));
+
+        long seconds = Duration.between(initialTime, finalTime)
+            .getSeconds();
+
+        assertThat(seconds).isEqualTo(30);
+    }
+
+    @Test
+    public void givenATimePlus30Seconds_whenRequestingSecondsBetween_thenExpect30() {
+        LocalTime initialTime = LocalTime.of(6, 30, 0);
+        LocalTime finalTime = initialTime.plus(Duration.ofSeconds(30));
+
+        long seconds = ChronoUnit.SECONDS.between(initialTime, finalTime);
+
+        assertThat(seconds).isEqualTo(30);
+    }
+
+    @Test
+    public void test2() {
+        Instant start = Instant.parse("2017-10-03T10:15:30.00Z");
+        Instant end = Instant.parse("2017-10-03T10:16:30.00Z");
+
+        Duration duration = Duration.between(start, end);
+
+        assertFalse(duration.isNegative());
+
+        assertEquals(60, duration.getSeconds());
+        assertEquals(1, duration.toMinutes());
+
+        Duration fromDays = Duration.ofDays(1);
+        assertEquals(86400, fromDays.getSeconds());
+
+        Duration fromMinutes = Duration.ofMinutes(60);
+        assertEquals(1, fromMinutes.toHours());
+
+        assertEquals(120, duration.plusSeconds(60)
+            .getSeconds());
+        assertEquals(30, duration.minusSeconds(30)
+            .getSeconds());
+
+        assertEquals(120, duration.plus(60, ChronoUnit.SECONDS)
+            .getSeconds());
+        assertEquals(30, duration.minus(30, ChronoUnit.SECONDS)
+            .getSeconds());
+
+        Duration fromChar1 = Duration.parse("P1DT1H10M10.5S");
+        Duration fromChar2 = Duration.parse("PT10M");
+    }
+
+}

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/dateapi/JavaPeriodUnitTest.java

@@ -1,18 +1,41 @@
 package com.baeldung.dateapi;
 
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+import java.time.LocalDate;
+import java.time.Period;
+import java.time.temporal.ChronoUnit;
+
 import org.apache.log4j.Logger;
 import org.junit.Test;
 
-import java.time.LocalDate;
-import java.time.Period;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-
 public class JavaPeriodUnitTest {
 
     private static final Logger LOG = Logger.getLogger(JavaPeriodUnitTest.class);
 
+    @Test
+    public void givenADatePlus5Days_whenRequestingPeriod_thenExpectFive() {
+        LocalDate initialDate = LocalDate.parse("2007-05-10");
+        LocalDate finalDate = initialDate.plus(Period.ofDays(5));
+
+        int days = Period.between(initialDate, finalDate)
+            .getDays();
+
+        assertThat(days).isEqualTo(5);
+    }
+
+    @Test
+    public void givenADatePlus5Days_whenRequestingDaysBetween_thenExpectFive() {
+        LocalDate initialDate = LocalDate.parse("2007-05-10");
+        LocalDate finalDate = initialDate.plus(Period.ofDays(5));
+
+        long days = ChronoUnit.DAYS.between(initialDate, finalDate);
+
+        assertThat(days).isEqualTo(5);
+    }
+
     @Test
     public void whenTestPeriod_thenOk() {
 
@@ -24,8 +47,10 @@ public class JavaPeriodUnitTest {
         LOG.info(String.format("Years:%d months:%d days:%d", period.getYears(), period.getMonths(), period.getDays()));
 
         assertFalse(period.isNegative());
-        assertEquals(56, period.plusDays(50).getDays());
-        assertEquals(9, period.minusMonths(2).getMonths());
+        assertEquals(56, period.plusDays(50)
+            .getDays());
+        assertEquals(9, period.minusMonths(2)
+            .getMonths());
 
         Period fromUnits = Period.of(3, 10, 10);
         Period fromDays = Period.ofDays(50);

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/datetime/UseLocalDateTimeUnitTest.java

@@ -7,12 +7,13 @@ import java.time.LocalDate;
 import java.time.LocalDateTime;
 import java.time.LocalTime;
 import java.time.Month;
+import java.time.ZoneOffset;
 
 import org.junit.Test;
 
 public class UseLocalDateTimeUnitTest {
 
-    UseLocalDateTime useLocalDateTime = new UseLocalDateTime();
+    private UseLocalDateTime useLocalDateTime = new UseLocalDateTime();
 
     @Test
     public void givenString_whenUsingParse_thenLocalDateTime() {
@@ -33,4 +34,28 @@ public class UseLocalDateTimeUnitTest {
         assertThat(endOfDayFromGivenDirectly.toLocalTime()).isEqualTo(LocalTime.MAX);
         assertThat(endOfDayFromGivenDirectly.toString()).isEqualTo("2018-06-23T23:59:59.999999999");
     }
+
+    @Test
+    public void givenLocalDateTimeInFebruary_whenRequestingMonth_thenMonthIsFebruary() {
+        LocalDateTime givenLocalDateTime = LocalDateTime.of(2015, Month.FEBRUARY, 20, 6, 30);
+
+        assertThat(givenLocalDateTime.getMonth()).isEqualTo(Month.FEBRUARY);
+    }
+
+    @Test
+    public void givenLocalDateTime_whenManipulating_thenResultIsAsExpected() {
+        LocalDateTime givenLocalDateTime = LocalDateTime.parse("2015-02-20T06:30:00");
+
+        LocalDateTime manipulatedLocalDateTime = givenLocalDateTime.plusDays(1);
+        manipulatedLocalDateTime = manipulatedLocalDateTime.minusHours(2);
+
+        assertThat(manipulatedLocalDateTime).isEqualTo(LocalDateTime.of(2015, Month.FEBRUARY, 21, 4, 30));
+    }
+
+    @Test
+    public void whenRequestTimeFromEpoch_thenResultIsAsExpected() {
+        LocalDateTime result = useLocalDateTime.ofEpochSecond(1465817690, ZoneOffset.UTC);
+
+        assertThat(result.toString()).isEqualTo("2016-06-13T11:34:50");
+    }
 }

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/datetime/UseLocalDateUnitTest.java

@@ -12,7 +12,7 @@ import org.junit.Test;
 
 public class UseLocalDateUnitTest {
 
-    UseLocalDate useLocalDate = new UseLocalDate();
+    private UseLocalDate useLocalDate = new UseLocalDate();
 
     @Test
     public void givenValues_whenUsingFactoryOf_thenLocalDate() {
@@ -88,4 +88,31 @@ public class UseLocalDateUnitTest {
         assertThat(endOfDayWithMax.toString()).isEqualTo("2018-06-23T23:59:59.999999999");
     }
 
+    @Test
+    public void givenTheYear2000_whenCheckingForLeapYear_thenReturnTrue() {
+        LocalDate given = LocalDate.parse("2000-06-23");
+
+        boolean leapYear = useLocalDate.isLeapYear(given);
+
+        assertThat(leapYear).isEqualTo(true);
+    }
+
+    @Test
+    public void givenTheYear2004_whenCheckingForLeapYear_thenReturnTrue() {
+        LocalDate given = LocalDate.parse("2004-06-23");
+
+        boolean leapYear = useLocalDate.isLeapYear(given);
+
+        assertThat(leapYear).isEqualTo(true);
+    }
+
+    @Test
+    public void givenTheYear2019_whenCheckingForLeapYear_thenReturnFalse() {
+        LocalDate given = LocalDate.parse("2019-06-23");
+
+        boolean leapYear = useLocalDate.isLeapYear(given);
+
+        assertThat(leapYear).isEqualTo(false);
+    }
+
 }

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/datetime/UseLocalTimeUnitTest.java

@@ -7,21 +7,30 @@ import org.junit.Test;
 
 public class UseLocalTimeUnitTest {
 
-    UseLocalTime useLocalTime = new UseLocalTime();
+    private UseLocalTime useLocalTime = new UseLocalTime();
 
     @Test
     public void givenValues_whenUsingFactoryOf_thenLocalTime() {
-        Assert.assertEquals("07:07:07", useLocalTime.getLocalTimeUsingFactoryOfMethod(7, 7, 7).toString());
+        Assert.assertEquals("07:07:07", useLocalTime.getLocalTimeUsingFactoryOfMethod(7, 7, 7)
+            .toString());
+    }
+
+    @Test
+    public void givenValues_whenUsingFactoryOfWithoutSeconds_thenLocalTime() {
+        Assert.assertEquals("07:07", useLocalTime.getLocalTimeUsingFactoryOfMethod(7, 7)
+            .toString());
     }
 
     @Test
     public void givenString_whenUsingParse_thenLocalTime() {
-        Assert.assertEquals("06:30", useLocalTime.getLocalTimeUsingParseMethod("06:30").toString());
+        Assert.assertEquals("06:30", useLocalTime.getLocalTimeUsingParseMethod("06:30")
+            .toString());
     }
 
     @Test
     public void givenTime_whenAddHour_thenLocalTime() {
-        Assert.assertEquals("07:30", useLocalTime.addAnHour(LocalTime.of(6, 30)).toString());
+        Assert.assertEquals("07:30", useLocalTime.addAnHour(LocalTime.of(6, 30))
+            .toString());
     }
 
     @Test

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/datetime/UseZonedDateTimeUnitTest.java

@@ -7,13 +7,14 @@ import java.time.LocalDateTime;
 import java.time.LocalTime;
 import java.time.ZoneId;
 import java.time.ZonedDateTime;
+import java.util.Set;
 
 import org.junit.Assert;
 import org.junit.Test;
 
 public class UseZonedDateTimeUnitTest {
 
-    UseZonedDateTime zonedDateTime = new UseZonedDateTime();
+    private UseZonedDateTime zonedDateTime = new UseZonedDateTime();
 
     @Test
     public void givenZoneId_thenZonedDateTime() {
@@ -22,6 +23,13 @@ public class UseZonedDateTimeUnitTest {
         Assert.assertEquals(zoneId, ZoneId.from(zonedDatetime));
     }
 
+    @Test
+    public void whenRequestingZones_thenAtLeastOneIsReturned() {
+        Set<String> allZoneIds = ZoneId.getAvailableZoneIds();
+
+        assertThat(allZoneIds.size()).isGreaterThan(1);
+    }
+
     @Test
     public void givenLocalDateOrZoned_whenSettingStartOfDay_thenReturnMidnightInAllCases() {
         LocalDate given = LocalDate.parse("2018-06-23");
@@ -42,4 +50,15 @@ public class UseZonedDateTimeUnitTest {
         assertThat(startOfOfDayWithMethod.toLocalTime()
             .toString()).isEqualTo("00:00");
     }
+
+    @Test
+    public void givenAStringWithTimeZone_whenParsing_thenEqualsExpected() {
+        ZonedDateTime resultFromString = zonedDateTime.getZonedDateTimeUsingParseMethod("2015-05-03T10:15:30+01:00[Europe/Paris]");
+        ZonedDateTime resultFromLocalDateTime = ZonedDateTime.of(2015, 5, 3, 11, 15, 30, 0, ZoneId.of("Europe/Paris"));
+
+        assertThat(resultFromString.getZone()).isEqualTo(ZoneId.of("Europe/Paris"));
+        assertThat(resultFromLocalDateTime.getZone()).isEqualTo(ZoneId.of("Europe/Paris"));
+
+        assertThat(resultFromString).isEqualTo(resultFromLocalDateTime);
+    }
 }

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/random/LegacyRandomDateTimesUnitTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.random;
+
+import org.junit.jupiter.api.RepeatedTest;
+
+import java.util.Date;
+import java.util.concurrent.TimeUnit;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class LegacyRandomDateTimesUnitTest {
+
+    private static final Date MIN_DATE = new Date(Long.MIN_VALUE);
+    private static final Date MAX_DATE = new Date(Long.MAX_VALUE);
+
+    @RepeatedTest(100)
+    void givenARange_WhenGenTimestamp_ShouldBeInRange() {
+        long aDay = TimeUnit.DAYS.toMillis(1);
+        long now = new Date().getTime();
+
+        Date hundredYearsAgo = new Date(now - aDay * 365 * 100);
+        Date tenDaysAgo = new Date(now - aDay * 10);
+
+        Date random = LegacyRandomDateTimes.between(hundredYearsAgo, tenDaysAgo);
+        assertThat(random).isBetween(hundredYearsAgo, tenDaysAgo);
+    }
+
+    @RepeatedTest(100)
+    void givenNoRange_WhenGenTimestamp_ShouldGenerateRandomTimestamps() {
+        Date random = LegacyRandomDateTimes.timestamp();
+
+        assertThat(random)
+                .isNotNull()
+                .isBetween(MIN_DATE, MAX_DATE);
+    }
+
+}

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/random/RandomDateTimesUnitTest.java

@@ -0,0 +1,27 @@
+package com.baeldung.random;
+
+import org.junit.jupiter.api.RepeatedTest;
+
+import java.time.Duration;
+import java.time.Instant;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class RandomDateTimesUnitTest {
+
+    @RepeatedTest(100)
+    void givenNoRange_WhenGenTimestamp_ShouldGenerateRandomTimestamps() {
+        Instant random = RandomDateTimes.timestamp();
+
+        assertThat(random).isBetween(Instant.MIN, Instant.MAX);
+    }
+
+    @RepeatedTest(100)
+    void givenARange_WhenGenTimestamp_ShouldBeInRange() {
+        Instant hundredYearsAgo = Instant.now().minus(Duration.ofDays(100 * 365));
+        Instant tenDaysAgo = Instant.now().minus(Duration.ofDays(10));
+
+        Instant random = RandomDateTimes.between(hundredYearsAgo, tenDaysAgo);
+        assertThat(random).isBetween(hundredYearsAgo, tenDaysAgo);
+    }
+}

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/random/RandomDatesUnitTest.java

@@ -0,0 +1,27 @@
+package com.baeldung.random;
+
+import org.junit.jupiter.api.RepeatedTest;
+
+import java.time.LocalDate;
+import java.time.Month;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class RandomDatesUnitTest {
+
+    @RepeatedTest(100)
+    void givenNoRange_WhenGenDate_ShouldGenerateRandomDates() {
+        LocalDate randomDay = RandomDates.date();
+
+        assertThat(randomDay).isAfter(LocalDate.MIN).isBefore(LocalDate.MAX);
+    }
+
+    @RepeatedTest(100)
+    void givenARange_WhenGenDate_ShouldBeInRange() {
+        LocalDate start = LocalDate.of(1989, Month.OCTOBER, 14);
+        LocalDate end = LocalDate.now();
+
+        LocalDate random = RandomDates.between(start, end);
+        assertThat(random).isAfter(start).isBefore(end);
+    }
+}

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/random/RandomTimesUnitTest.java

@@ -0,0 +1,20 @@
+package com.baeldung.random;
+
+import org.junit.jupiter.api.RepeatedTest;
+
+import java.time.LocalTime;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class RandomTimesUnitTest {
+
+    @RepeatedTest(100)
+    void givenARange_WhenGenTime_ShouldBeInRange() {
+        LocalTime morning = LocalTime.of(8, 30);
+        LocalTime randomTime = RandomTimes.between(LocalTime.MIDNIGHT, morning);
+
+        assertThat(randomTime)
+                .isAfter(LocalTime.MIDNIGHT).isBefore(morning)
+                .isAfter(LocalTime.MIN).isBefore(LocalTime.MAX);
+    }
+}