[] - Moved artices / codes from from the core-java related modules

2018-09-02 01:37:11 +05:30
parent 3b9ce7537f
commit 4f18b712f9
15 changed files with 15 additions and 12 deletions
--- a/core-java-collections/src/test/java/com/baeldung/findanelement/FindACustomerInGivenListUnitTest.java
+++ b/core-java-collections/src/test/java/com/baeldung/findanelement/FindACustomerInGivenListUnitTest.java
@@ -0,0 +1,158 @@
+package com.baeldung.findanelement;
+
+import static org.junit.Assert.*;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.Test;
+
+public class FindACustomerInGivenListUnitTest {
+
+    private static List<Customer> customers = new ArrayList<>();
+
+    static {
+        customers.add(new Customer(1, "Jack"));
+        customers.add(new Customer(2, "James"));
+        customers.add(new Customer(3, "Sam"));
+    }
+
+    private static FindACustomerInGivenList findACustomerInGivenList = new FindACustomerInGivenList();
+
+    @Test
+    public void givenAnIndex_whenFoundUsingGivenIndex_thenReturnCustomer() {
+        Customer customer = findACustomerInGivenList.findUsingGivenIndex(0, customers);
+
+        assertEquals(1, customer.getId());
+    }
+
+    @Test
+    public void givenAnIndex_whenNotFoundUsingGivenIndex_thenReturnNull() {
+        Customer customer = findACustomerInGivenList.findUsingGivenIndex(5, customers);
+
+        assertNull(customer);
+    }
+
+    @Test
+    public void givenACustomer_whenFoundUsingContains_thenReturnTrue() {
+        Customer james = new Customer(2, "James");
+        boolean isJamesPresent = findACustomerInGivenList.findUsingContains(james, customers);
+
+        assertEquals(true, isJamesPresent);
+    }
+
+    @Test
+    public void givenACustomer_whenNotFoundUsingContains_thenReturnFalse() {
+        Customer john = new Customer(5, "John");
+        boolean isJohnPresent = findACustomerInGivenList.findUsingContains(john, customers);
+
+        assertEquals(false, isJohnPresent);
+    }
+
+    @Test
+    public void givenACustomer_whenFoundUsingIndexOf_thenReturnItsIndex() {
+        Customer james = new Customer(2, "James");
+        int indexOfJames = findACustomerInGivenList.findUsingIndexOf(james, customers);
+
+        assertEquals(1, indexOfJames);
+    }
+
+    @Test
+    public void givenACustomer_whenNotFoundUsingIndexOf_thenReturnMinus1() {
+        Customer john = new Customer(5, "John");
+        int indexOfJohn = findACustomerInGivenList.findUsingIndexOf(john, customers);
+
+        assertEquals(-1, indexOfJohn);
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameFoundUsingIterator_thenReturnCustomer() {
+        Customer james = findACustomerInGivenList.findUsingIterator("James", customers);
+
+        assertEquals("James", james.getName());
+        assertEquals(2, james.getId());
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameNotFoundUsingIterator_thenReturnNull() {
+        Customer john = findACustomerInGivenList.findUsingIterator("John", customers);
+
+        assertNull(john);
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameFoundUsingEnhancedFor_thenReturnCustomer() {
+        Customer james = findACustomerInGivenList.findUsingEnhancedForLoop("James", customers);
+
+        assertEquals("James", james.getName());
+        assertEquals(2, james.getId());
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameNotFoundUsingEnhancedFor_thenReturnNull() {
+        Customer john = findACustomerInGivenList.findUsingEnhancedForLoop("John", customers);
+
+        assertNull(john);
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameFoundUsingStream_thenReturnCustomer() {
+        Customer james = findACustomerInGivenList.findUsingStream("James", customers);
+
+        assertEquals("James", james.getName());
+        assertEquals(2, james.getId());
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameNotFoundUsingStream_thenReturnNull() {
+        Customer john = findACustomerInGivenList.findUsingStream("John", customers);
+
+        assertNull(john);
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameFoundUsingParallelStream_thenReturnCustomer() {
+        Customer james = findACustomerInGivenList.findUsingParallelStream("James", customers);
+
+        assertEquals("James", james.getName());
+        assertEquals(2, james.getId());
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameNotFoundUsingParallelStream_thenReturnNull() {
+        Customer john = findACustomerInGivenList.findUsingParallelStream("John", customers);
+
+        assertNull(john);
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameFoundUsingApacheCommon_thenReturnCustomer() {
+        Customer james = findACustomerInGivenList.findUsingApacheCommon("James", customers);
+
+        assertEquals("James", james.getName());
+        assertEquals(2, james.getId());
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameNotFoundUsingApacheCommon_thenReturnNull() {
+        Customer john = findACustomerInGivenList.findUsingApacheCommon("John", customers);
+
+        assertNull(john);
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameFoundUsingGuava_thenReturnCustomer() {
+        Customer james = findACustomerInGivenList.findUsingGuava("James", customers);
+
+        assertEquals("James", james.getName());
+        assertEquals(2, james.getId());
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameNotFoundUsingGuava_thenReturnNull() {
+        Customer john = findACustomerInGivenList.findUsingGuava("John", customers);
+
+        assertNull(john);
+    }
+
+}
--- a/core-java-collections/src/test/java/com/baeldung/hashtable/HashtableUnitTest.java
+++ b/core-java-collections/src/test/java/com/baeldung/hashtable/HashtableUnitTest.java
@@ -0,0 +1,274 @@
+package com.baeldung.hashtable;
+
+import java.util.ConcurrentModificationException;
+import java.util.Enumeration;
+import java.util.Hashtable;
+import java.util.Iterator;
+import java.util.Map;
+
+import static org.junit.Assert.*;
+import static org.hamcrest.Matchers.*;
+import org.junit.Test;
+
+public class HashtableUnitTest {
+
+    @Test
+    public void whenPutAndGet_thenReturnsValue() {
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+
+        Word word = new Word("cat");
+        table.put(word, "an animal");
+
+        String definition = table.get(word);
+
+        assertEquals("an animal", definition);
+
+        definition = table.remove(word);
+
+        assertEquals("an animal", definition);
+    }
+
+    @Test
+    public void whenThesameInstanceOfKey_thenReturnsValue() {
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        Word word = new Word("cat");
+        table.put(word, "an animal");
+        String extracted = table.get(word);
+        assertEquals("an animal", extracted);
+    }
+
+    @Test
+    public void whenEqualsOverridden_thenReturnsValue() {
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        Word word = new Word("cat");
+        table.put(word, "an animal");
+        String extracted = table.get(new Word("cat"));
+        assertEquals("an animal", extracted);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void whenNullKey_thenException() {
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        table.put(null, "an animal");
+    }
+
+    @Test(expected = ConcurrentModificationException.class)
+    public void whenIterate_thenFailFast() {
+
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        table.put(new Word("cat"), "an animal");
+        table.put(new Word("dog"), "another animal");
+
+        Iterator<Word> it = table.keySet().iterator();
+        System.out.println("iterator created");
+
+        table.remove(new Word("dog"));
+        System.out.println("element removed");
+
+        while (it.hasNext()) {
+            Word key = it.next();
+            System.out.println(table.get(key));
+        }
+    }
+
+    @Test
+    public void whenEnumerate_thenNotFailFast() {
+
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        table.put(new Word("1"), "one");
+        table.put(new Word("2"), "two");
+        table.put(new Word("3"), "three");
+        table.put(new Word("4"), "four");
+        table.put(new Word("5"), "five");
+        table.put(new Word("6"), "six");
+        table.put(new Word("7"), "seven");
+        table.put(new Word("8"), "eight");
+
+        Enumeration<Word> enumKey = table.keys();
+        System.out.println("Enumeration created");
+        table.remove(new Word("1"));
+        System.out.println("element removed");
+        while (enumKey.hasMoreElements()) {
+            Word key = enumKey.nextElement();
+            System.out.println(table.get(key));
+        }
+    }
+
+    @Test
+    public void whenAddElements_thenIterationOrderUnpredicable() {
+
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        table.put(new Word("1"), "one");
+        table.put(new Word("2"), "two");
+        table.put(new Word("3"), "three");
+        table.put(new Word("4"), "four");
+        table.put(new Word("5"), "five");
+        table.put(new Word("6"), "six");
+        table.put(new Word("7"), "seven");
+        table.put(new Word("8"), "eight");
+
+        Iterator<Map.Entry<Word, String>> it = table.entrySet().iterator();
+        while (it.hasNext()) {
+            Map.Entry<Word, String> entry = it.next();
+            System.out.println(entry.getValue());
+        }
+    }
+
+    @Test
+    public void whenGetOrDefault_thenDefaultGot() {
+
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        table.put(new Word("cat"), "a small domesticated carnivorous mammal");
+        Word key = new Word("dog");
+        String definition;
+
+        // old way
+        /* if (table.containsKey(key)) {
+            definition = table.get(key);
+        } else {
+            definition = "not found";
+        }*/
+
+        // new way
+        definition = table.getOrDefault(key, "not found");
+
+        assertThat(definition, is("not found"));
+    }
+
+    @Test
+    public void whenPutifAbsent_thenNotRewritten() {
+
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        table.put(new Word("cat"), "a small domesticated carnivorous mammal");
+
+        String definition = "an animal";
+        // old way
+        /* if (!table.containsKey(new Word("cat"))) {
+            table.put(new Word("cat"), definition);
+        }*/
+        // new way
+        table.putIfAbsent(new Word("cat"), definition);
+
+        assertThat(table.get(new Word("cat")), is("a small domesticated carnivorous mammal"));
+    }
+
+    @Test
+    public void whenRemovePair_thenCheckKeyAndValue() {
+
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        table.put(new Word("cat"), "a small domesticated carnivorous mammal");
+
+        // old way
+        /* if (table.get(new Word("cat")).equals("an animal")) {
+            table.remove(new Word("cat"));
+        }*/
+
+        // new way
+        boolean result = table.remove(new Word("cat"), "an animal");
+
+        assertThat(result, is(false));
+    }
+
+    @Test
+    public void whenReplacePair_thenValueChecked() {
+
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        table.put(new Word("cat"), "a small domesticated carnivorous mammal");
+
+        String definition = "an animal";
+
+        // old way
+        /* if (table.containsKey(new Word("cat")) && table.get(new Word("cat")).equals("a small domesticated carnivorous mammal")) {
+            table.put(new Word("cat"), definition);
+        }*/
+        // new way
+        table.replace(new Word("cat"), "a small domesticated carnivorous mammal", definition);
+
+        assertThat(table.get(new Word("cat")), is("an animal"));
+
+    }
+
+    @Test
+    public void whenKeyIsAbsent_thenNotRewritten() {
+
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        table.put(new Word("cat"), "a small domesticated carnivorous mammal");
+
+        // old way
+        /* if (!table.containsKey(cat)) {
+            String definition = "an animal";// calculate
+            table.put(new Word("cat"), definition);
+        }
+        */
+        // new way
+
+        table.computeIfAbsent(new Word("cat"), key -> "an animal");
+        assertThat(table.get(new Word("cat")), is("a small domesticated carnivorous mammal"));
+
+    }
+
+    @Test
+    public void whenKeyIsPresent_thenComputeIfPresent() {
+
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        table.put(new Word("cat"), "a small domesticated carnivorous mammal");
+
+        Word cat = new Word("cat");
+        // old way
+        /* if (table.containsKey(cat)) {
+            String concatination = cat.getName() + " - " + table.get(cat);
+            table.put(cat, concatination);
+        }*/
+
+        // new way
+        table.computeIfPresent(cat, (key, value) -> key.getName() + " - " + value);
+
+        assertThat(table.get(cat), is("cat - a small domesticated carnivorous mammal"));
+
+    }
+
+    @Test
+    public void whenCompute_thenForAllKeys() {
+
+        Hashtable<String, Integer> table = new Hashtable<String, Integer>();
+        String[] animals = { "cat", "dog", "dog", "cat", "bird", "mouse", "mouse" };
+        for (String animal : animals) {
+            table.compute(animal, (key, value) -> (value == null ? 1 : value + 1));
+        }
+        assertThat(table.values(), hasItems(2, 2, 2, 1));
+
+    }
+
+    @Test
+    public void whenInsteadOfCompute_thenMerge() {
+
+        Hashtable<String, Integer> table = new Hashtable<String, Integer>();
+        String[] animals = { "cat", "dog", "dog", "cat", "bird", "mouse", "mouse" };
+        for (String animal : animals) {
+            table.merge(animal, 1, (oldValue, value) -> (oldValue + value));
+        }
+        assertThat(table.values(), hasItems(2, 2, 2, 1));
+    }
+
+    @Test
+    public void whenForeach_thenIterate() {
+
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        table.put(new Word("cat"), "a small domesticated carnivorous mammal");
+        table.put(new Word("dog"), "another animal");
+        table.forEach((k, v) -> System.out.println(k.getName() + " - " + v)
+
+        );
+    }
+
+    @Test
+    public void whenReplaceall_thenNoIterationNeeded() {
+
+        Hashtable<Word, String> table = new Hashtable<Word, String>();
+        table.put(new Word("cat"), "a small domesticated carnivorous mammal");
+        table.put(new Word("dog"), "another animal");
+        table.replaceAll((k, v) -> k.getName() + " - " + v);
+
+        assertThat(table.values(), hasItems("cat - a small domesticated carnivorous mammal", "dog - another animal"));
+    }
+}
--- a/core-java-collections/src/test/java/com/baeldung/iterators/IteratorsUnitTest.java
+++ b/core-java-collections/src/test/java/com/baeldung/iterators/IteratorsUnitTest.java
@@ -0,0 +1,40 @@
+package com.baeldung.iterators;
+
+import static com.baeldung.iterators.Iterators.failFast1;
+import static com.baeldung.iterators.Iterators.failFast2;
+import static com.baeldung.iterators.Iterators.failSafe1;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import java.util.ConcurrentModificationException;
+
+import org.junit.Test;
+
+/**
+ * Source code https://github.com/eugenp/tutorials
+ *
+ * @author Santosh Thakur
+ */
+
+public class IteratorsUnitTest {
+
+    @Test
+    public void whenFailFast_ThenThrowsException() {
+        assertThatThrownBy(() -> {
+            failFast1();
+        }).isInstanceOf(ConcurrentModificationException.class);
+    }
+
+    @Test
+    public void whenFailFast_ThenThrowsExceptionInSecondIteration() {
+        assertThatThrownBy(() -> {
+            failFast2();
+        }).isInstanceOf(ConcurrentModificationException.class);
+    }
+
+    @Test
+    public void whenFailSafe_ThenDoesNotThrowException() {
+        assertThat(failSafe1()).isGreaterThanOrEqualTo(0);
+    }
+
+}
--- a/core-java-collections/src/test/java/com/baeldung/java/list/CopyListServiceUnitTest.java
+++ b/core-java-collections/src/test/java/com/baeldung/java/list/CopyListServiceUnitTest.java
@@ -0,0 +1,133 @@
+package com.baeldung.java.list;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.Before;
+import org.junit.Test;
+
+public class CopyListServiceUnitTest {
+
+    List<Flower> flowers;
+
+    private CopyListService copyListService;
+
+    @Before
+    public void init() {
+        this.copyListService = new CopyListService();
+        this.flowers = new ArrayList<>();
+
+        Flower poppy = new Flower("Poppy", 12);
+        flowers.add(poppy);
+        Flower anemone = new Flower("Anemone", 8);
+        flowers.add(anemone);
+        Flower catmint = new Flower("Catmint", 12);
+        flowers.add(catmint);
+        Flower diascia = new Flower("Diascia", 5);
+        flowers.add(diascia);
+        Flower iris = new Flower("Iris", 3);
+        flowers.add(iris);
+        Flower pansy = new Flower("Pansy", 5);
+        flowers.add(pansy);
+    }
+
+    @Test
+    public void givenAList_whenListDoesNotHaveNullElements_thenReturnAnotherListWithTheSameElementsByConstructor() {
+        List<Flower> copy = copyListService.copyListByConstructor(flowers);
+        assertEquals(copy.size(), flowers.size());
+        assertTrue(copy.containsAll(flowers));
+    }
+
+    @Test
+    public void givenAList_whenListDoesNotHaveNullElements_thenReturnAnotherListWithOneModifiedElementByConstructor() {
+        List<Flower> copy = copyListService.copyListByConstructorAndEditOneFlowerInTheNewList(flowers);
+        assertEquals(copy.size(), flowers.size());
+        assertTrue(copy.containsAll(flowers));
+    }
+
+    @Test
+    public void givenAList_whenListDoesNotHaveNullElements_thenReturnAnotherListWithTheSameElementsByAddAllmethod() {
+        List<Flower> copy = copyListService.copyListByAddAllMethod(flowers);
+        assertEquals(copy.size(), flowers.size());
+        assertTrue(copy.containsAll(flowers));
+    }
+
+    @Test
+    public void givenAList_whenListDoesNotHaveNullElements_thenReturnAnotherListWithOneModifiedElementByAddAllmethod() {
+        List<Flower> copy = copyListService.copyListByAddAllMethodAndEditOneFlowerInTheNewList(flowers);
+        assertEquals(copy.size(), flowers.size());
+        assertTrue(copy.containsAll(flowers));
+    }
+
+    @Test
+    public void givenAList_whenListsHaveSameSize_thenReturnAnotherListWithTheSameElementsByCopyMethod() {
+        List<Integer> source = Arrays.asList(1,2,3);
+        List<Integer> dest = Arrays.asList(4,5,6);
+
+        dest = copyListService.copyListByCopyMethod(source, dest);
+        assertEquals(dest.size(), source.size());
+        assertTrue(dest.containsAll(source));
+    }
+
+    @Test
+    public void givenAList_whenListsHaveDifferentSize_thenReturnAnotherListWithTheSameElementsByCopyMethod() {
+        List<Integer> source = Arrays.asList(1,2,3);
+        List<Integer> dest = Arrays.asList(5,6,7,8,9,10);
+
+        dest = copyListService.copyListByCopyMethod(source, dest);
+        assertNotEquals(dest.size(), source.size());
+        assertTrue(dest.containsAll(source));
+    }
+
+    @Test
+    public void givenAList_whenListDoesNotHaveNullElements_thenReturnAnotherListWithTheSameElementsByStreamProcess() {
+        List<Flower> copy = copyListService.copyListByStream(flowers);
+        assertEquals(copy.size(), flowers.size());
+        assertTrue(copy.containsAll(flowers));
+    }
+
+    @Test
+    public void givenAList_whenListDoesNotHaveNullElements_thenReturnAnotherListWithOneElementLessByStreamProcess() {
+        List<Flower> copy = copyListService.copyListByStreamAndSkipFirstElement(flowers);
+        assertNotEquals(copy.size(), flowers.size());
+        assertEquals(copy.size() + 1, flowers.size());
+        assertFalse(copy.containsAll(flowers));
+    }
+
+    @Test
+    public void givenAList_whenListDoesNotHaveNullElements_thenReturnAnotherListWithFilterElementsByStreamProcess() {
+        List<Flower> copy = copyListService.copyListByStreamWithFilter(flowers, 5);
+        assertNotEquals(copy.size(), flowers.size());
+        assertEquals(copy.size() + 3, flowers.size());
+        assertFalse(copy.containsAll(flowers));
+    }
+
+    @Test
+    public void givenAList_whenListIsNull_thenReturnEmptyListByStreamProcess() {
+        List<Flower> copy = copyListService.copyListByStreamWithOptional(null);
+        assertNotNull(copy);
+        assertEquals(copy.size(), 0);
+    }
+
+    @Test
+    public void givenAList_whenListIsNotNull_thenReturnAnotherListWithTheElementsByStreamProcess() {
+        List<Flower> copy = copyListService.copyListByStreamWithOptional(flowers);
+        assertEquals(copy.size(), flowers.size());
+        assertTrue(copy.containsAll(flowers));
+    }
+
+    @Test
+    public void givenAList_whenListIsNotNull_thenReturnAnotherListWithOneElementLessByStreamProcess() {
+        List<Flower> copy = copyListService.copyListByStreamWithOptionalAndSkip(flowers);
+        assertNotEquals(copy.size(), flowers.size());
+        assertEquals(copy.size() + 1, flowers.size());
+        assertFalse(copy.containsAll(flowers));
+    }
+}
--- a/core-java-collections/src/test/java/com/baeldung/java8/Java8MaxMinUnitTest.java
+++ b/core-java-collections/src/test/java/com/baeldung/java8/Java8MaxMinUnitTest.java
@@ -0,0 +1,74 @@
+package com.baeldung.java8;
+
+import com.baeldung.java_8_features.Car;
+import com.baeldung.java_8_features.Person;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+import java.util.NoSuchElementException;
+
+import static org.junit.Assert.assertEquals;
+
+public class Java8MaxMinUnitTest {
+
+    @Test
+    public void whenListIsOfIntegerThenMaxCanBeDoneUsingIntegerComparator() {
+        //given
+        final List<Integer> listOfIntegers = Arrays.asList(1, 2, 3, 4, 56, 7, 89, 10);
+        final Integer expectedResult = 89;
+
+        //then
+        final Integer max = listOfIntegers
+          .stream()
+          .mapToInt(v -> v)
+          .max().orElseThrow(NoSuchElementException::new);
+
+        assertEquals("Should be 89", expectedResult, max);
+    }
+
+    @Test
+    public void whenListIsOfPersonObjectThenMinCanBeDoneUsingCustomComparatorThroughLambda() {
+        //given
+        final Person alex = new Person("Alex", 23);
+        final Person john = new Person("John", 40);
+        final Person peter = new Person("Peter", 32);
+        final List<Person> people = Arrays.asList(alex, john, peter);
+
+        //then
+        final Person minByAge = people
+          .stream()
+          .min(Comparator.comparing(Person::getAge))
+          .orElseThrow(NoSuchElementException::new);
+
+        assertEquals("Should be Alex", alex, minByAge);
+    }
+
+    @Test
+    public void whenArrayIsOfIntegerThenMinUsesIntegerComparator() {
+        int[] integers = new int[] { 20, 98, 12, 7, 35 };
+
+        int min = Arrays.stream(integers)
+            .min()
+            .getAsInt();
+
+        assertEquals(7, min);
+    }
+
+    @Test
+    public void whenArrayIsOfCustomTypeThenMaxUsesCustomComparator() {
+        final Car porsche = new Car("Porsche 959", 319);
+        final Car ferrari = new Car("Ferrari 288 GTO", 303);
+        final Car bugatti = new Car("Bugatti Veyron 16.4 Super Sport", 415);
+        final Car mcLaren = new Car("McLaren F1", 355);
+        final Car[] fastCars = { porsche, ferrari, bugatti, mcLaren };
+
+        final Car maxBySpeed = Arrays.stream(fastCars)
+            .max(Comparator.comparing(Car::getTopSpeed))
+            .orElseThrow(NoSuchElementException::new);
+
+        assertEquals(bugatti, maxBySpeed);
+    }
+}
--- a/core-java-collections/src/test/java/com/baeldung/shufflingcollections/ShufflingCollectionsUnitTest.java
+++ b/core-java-collections/src/test/java/com/baeldung/shufflingcollections/ShufflingCollectionsUnitTest.java
@@ -0,0 +1,70 @@
+package com.baeldung.shufflingcollections;
+
+import org.junit.Test;
+
+import java.util.*;
+import java.util.stream.Collectors;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ShufflingCollectionsUnitTest {
+
+    @Test
+    public void whenShufflingList_thenListIsShuffled() {
+        List<String> students = Arrays.asList("Foo", "Bar", "Baz", "Qux");
+
+        System.out.println("List before shuffling:");
+        System.out.println(students);
+
+        Collections.shuffle(students);
+        System.out.println("List after shuffling:");
+        System.out.println(students);
+    }
+
+    @Test
+    public void whenShufflingMapEntries_thenValuesAreShuffled() {
+        Map<Integer, String> studentsById = new HashMap<>();
+        studentsById.put(1, "Foo");
+        studentsById.put(2, "Bar");
+        studentsById.put(3, "Baz");
+        studentsById.put(4, "Qux");
+
+        System.out.println("Students before shuffling:");
+        System.out.println(studentsById.values());
+
+        List<Map.Entry<Integer, String>> shuffledStudentEntries = new ArrayList<>(studentsById.entrySet());
+        Collections.shuffle(shuffledStudentEntries);
+
+        List<String> shuffledStudents = shuffledStudentEntries.stream()
+                .map(Map.Entry::getValue)
+                .collect(Collectors.toList());
+
+        System.out.println("Students after shuffling");
+        System.out.println(shuffledStudents);
+    }
+
+    @Test
+    public void whenShufflingSet_thenElementsAreShuffled() {
+        Set<String> students = new HashSet<>(Arrays.asList("Foo", "Bar", "Baz", "Qux"));
+
+        System.out.println("Set before shuffling:");
+        System.out.println(students);
+
+        List<String> studentList = new ArrayList<>(students);
+
+        Collections.shuffle(studentList);
+        System.out.println("Shuffled set elements:");
+        System.out.println(studentList);
+    }
+
+    @Test
+    public void whenShufflingWithSameRandomness_thenElementsAreShuffledDeterministically() {
+        List<String> students_1 = Arrays.asList("Foo", "Bar", "Baz", "Qux");
+        List<String> students_2 = Arrays.asList("Foo", "Bar", "Baz", "Qux");
+
+        Collections.shuffle(students_1, new Random(5));
+        Collections.shuffle(students_2, new Random(5));
+
+        assertThat(students_1).isEqualTo(students_2);
+    }
+}