#BAEL-16633 split Core Java 9 module - improved features

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

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

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

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+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-9</artifactId>
+    <version>0.2-SNAPSHOT</version>
+    <name>core-java-9</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.jayway.awaitility</groupId>
+            <artifactId>awaitility</artifactId>
+            <version>${awaitility.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-runner</artifactId>
+            <version>${junit.platform.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-9</finalName>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <pluginRepositories>
+        <pluginRepository>
+            <id>apache.snapshots</id>
+            <url>http://repository.apache.org/snapshots/</url>
+        </pluginRepository>
+    </pluginRepositories>
+
+    <properties>
+        <!-- testing -->
+        <assertj.version>3.10.0</assertj.version>
+        <junit.platform.version>1.2.0</junit.platform.version>
+        <awaitility.version>1.7.0</awaitility.version>
+        <maven.compiler.source>1.9</maven.compiler.source>
+        <maven.compiler.target>1.9</maven.compiler.target>
+        <guava.version>25.1-jre</guava.version>
+    </properties>
+
+</project>

core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/Java9OptionalTest.java

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+package com.baeldung.java9;
+
+public class Java9OptionalTest {
+    @Test
+    public void givenOptionalOfSome_whenToStream_thenShouldTreatItAsOneElementStream() {
+        //given
+        Optional<String> value = Optional.of("a");
+
+        //when
+        List<String> collect = value.stream().map(String::toUpperCase).collect(Collectors.toList());
+
+        //then
+        assertThat(collect).hasSameElementsAs(List.of("A"));
+    }
+
+    @Test
+    public void givenOptionalOfNone_whenToStream_thenShouldTreatItAsZeroElementStream() {
+        //given
+        Optional<String> value = Optional.empty();
+
+        //when
+        List<String> collect = value.stream().map(String::toUpperCase).collect(Collectors.toList());
+
+        //then
+        assertThat(collect).isEmpty();
+    }
+
+    @Test
+    public void givenOptional_whenPresent_thenShouldExecuteProperCallback() {
+        //given
+        Optional<String> value = Optional.of("properValue");
+        AtomicInteger successCounter = new AtomicInteger(0);
+        AtomicInteger onEmptyOptionalCounter = new AtomicInteger(0);
+
+        //when
+        value.ifPresentOrElse((v) -> successCounter.incrementAndGet(), onEmptyOptionalCounter::incrementAndGet);
+
+        //then
+        assertThat(successCounter.get()).isEqualTo(1);
+        assertThat(onEmptyOptionalCounter.get()).isEqualTo(0);
+    }
+
+    @Test
+    public void givenOptional_whenNotPresent_thenShouldExecuteProperCallback() {
+        //given
+        Optional<String> value = Optional.empty();
+        AtomicInteger successCounter = new AtomicInteger(0);
+        AtomicInteger onEmptyOptionalCounter = new AtomicInteger(0);
+
+        //when
+        value.ifPresentOrElse((v) -> successCounter.incrementAndGet(), onEmptyOptionalCounter::incrementAndGet);
+
+        //then
+        assertThat(successCounter.get()).isEqualTo(0);
+        assertThat(onEmptyOptionalCounter.get()).isEqualTo(1);
+    }
+
+    @Test
+    public void givenOptional_whenPresent_thenShouldTakeAValueFromIt() {
+        //given
+        String expected = "properValue";
+        Optional<String> value = Optional.of(expected);
+        Optional<String> defaultValue = Optional.of("default");
+
+        //when
+        Optional<String> result = value.or(() -> defaultValue);
+
+        //then
+        assertThat(result.get()).isEqualTo(expected);
+    }
+
+    @Test
+    public void givenOptional_whenEmpty_thenShouldTakeAValueFromOr() {
+        //given
+        String defaultString = "default";
+        Optional<String> value = Optional.empty();
+        Optional<String> defaultValue = Optional.of(defaultString);
+
+        //when
+        Optional<String> result = value.or(() -> defaultValue);
+
+        //then
+        assertThat(result.get()).isEqualTo(defaultString);
+    }
+}

core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/concurrent/future/CompletableFutureUnitTest.java

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+package com.baeldung.java9.concurrent.future;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+import org.junit.Test;
+
+public class CompletableFutureUnitTest {
+    @Test
+    public void testDelay () throws Exception {
+        Object input = new Object();
+        CompletableFuture<Object> future = new CompletableFuture<>();
+        future.completeAsync(() -> input, CompletableFuture.delayedExecutor(1, TimeUnit.SECONDS));
+        
+        Thread.sleep(100);
+        
+        assertFalse(future.isDone());
+        
+        Thread.sleep(1000);
+        assertTrue(future.isDone());
+        assertSame(input, future.get());
+    }
+
+    @Test
+    public void testTimeoutTriggered () throws Exception {
+        CompletableFuture<Object> future = new CompletableFuture<>();
+        future.orTimeout(1, TimeUnit.SECONDS);
+        
+        Thread.sleep(1100);
+        
+        assertTrue(future.isDone());
+        
+        try {
+            future.get();
+        } catch (ExecutionException e) {
+            assertTrue(e.getCause() instanceof TimeoutException);
+        }
+    }
+
+    @Test
+    public void testTimeoutNotTriggered () throws Exception {
+        Object input = new Object();
+        CompletableFuture<Object> future = new CompletableFuture<>();
+        
+        future.orTimeout(1, TimeUnit.SECONDS);
+        
+        Thread.sleep(100);
+        
+        future.complete(input);
+        
+        Thread.sleep(1000);
+        
+        assertTrue(future.isDone());
+        assertSame(input, future.get());
+    }
+    
+    
+
+    @Test
+    public void completeOnTimeout () throws Exception {
+        Object input = new Object();
+        CompletableFuture<Object> future = new CompletableFuture<>();
+        future.completeOnTimeout(input, 1, TimeUnit.SECONDS);
+        
+        Thread.sleep(1100);
+        
+        assertTrue(future.isDone());
+        assertSame(input, future.get());
+    }
+}

core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/language/Java9ObjectsAPIUnitTest.java

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+package com.baeldung.java9.language;
+
+import org.junit.Test;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+
+import static org.hamcrest.Matchers.*;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+public class Java9ObjectsAPIUnitTest {
+
+    private List<String> aMethodReturningNullList(){
+        return null;
+    }
+
+    @Test
+    public void givenNullObject_whenRequireNonNullElse_thenElse(){
+        List<String> aList = Objects.<List>requireNonNullElse(
+                aMethodReturningNullList(), Collections.EMPTY_LIST);
+        assertThat(aList, is(Collections.EMPTY_LIST));
+    }
+
+    private List<String> aMethodReturningNonNullList(){
+        return List.of("item1", "item2");
+    }
+
+    @Test
+    public void givenObject_whenRequireNonNullElse_thenObject(){
+        List<String> aList = Objects.<List>requireNonNullElse(
+                aMethodReturningNonNullList(), Collections.EMPTY_LIST);
+        assertThat(aList, is(List.of("item1", "item2")));
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenNull_whenRequireNonNullElse_thenException(){
+        Objects.<List>requireNonNullElse(null, null);
+    }
+
+    @Test
+    public void givenObject_whenRequireNonNullElseGet_thenObject(){
+        List<String> aList = Objects.<List>requireNonNullElseGet(null, List::of);
+        assertThat(aList, is(List.of()));
+    }
+
+    @Test
+    public void givenNumber_whenInvokeCheckIndex_thenNumber(){
+        int length = 5;
+        assertThat(Objects.checkIndex(4, length), is(4));
+    }
+
+    @Test(expected = IndexOutOfBoundsException.class)
+    public void givenOutOfRangeNumber_whenInvokeCheckIndex_thenException(){
+        int length = 5;
+        Objects.checkIndex(5, length);
+    }
+
+
+    @Test
+    public void givenSubRange_whenCheckFromToIndex_thenNumber(){
+        int length = 6;
+        assertThat(Objects.checkFromToIndex(2,length,length), is(2));
+    }
+
+    @Test(expected = IndexOutOfBoundsException.class)
+    public void givenInvalidSubRange_whenCheckFromToIndex_thenException(){
+        int length = 6;
+        Objects.checkFromToIndex(2,7,length);
+    }
+
+
+    @Test
+    public void givenSubRange_whenCheckFromIndexSize_thenNumber(){
+        int length = 6;
+        assertThat(Objects.checkFromIndexSize(2,3,length), is(2));
+    }
+
+    @Test(expected = IndexOutOfBoundsException.class)
+    public void givenInvalidSubRange_whenCheckFromIndexSize_thenException(){
+        int length = 6;
+        Objects.checkFromIndexSize(2, 6, length);
+    }
+
+
+}

core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/language/collections/ListFactoryMethodsUnitTest.java

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+package com.baeldung.java9.language.collections;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+public class ListFactoryMethodsUnitTest {
+
+    @Test
+    public void whenListCreated_thenSuccess() {
+        List<String> traditionlList = new ArrayList<String>();
+        traditionlList.add("foo");
+        traditionlList.add("bar");
+        traditionlList.add("baz");
+        List<String> factoryCreatedList = List.of("foo", "bar", "baz");
+        assertEquals(traditionlList, factoryCreatedList);
+    }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public void onElemAdd_ifUnSupportedOpExpnThrown_thenSuccess() {
+        List<String> list = List.of("foo", "bar");
+        list.add("baz");
+    }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public void onElemModify_ifUnSupportedOpExpnThrown_thenSuccess() {
+        List<String> list = List.of("foo", "bar");
+        list.set(0, "baz");
+    }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public void onElemRemove_ifUnSupportedOpExpnThrown_thenSuccess() {
+        List<String> list = List.of("foo", "bar");
+        list.remove("foo");
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void onNullElem_ifNullPtrExpnThrown_thenSuccess() {
+        List.of("foo", "bar", null);
+    }
+
+    @Test
+    public void ifNotArrayList_thenSuccess() {
+        List<String> list = List.of("foo", "bar");
+        assertFalse(list instanceof ArrayList);
+    }
+
+    @Test
+    public void ifListSizeIsOne_thenSuccess() {
+        int[] arr = { 1, 2, 3, 4 };
+        List<int[]> list = List.of(arr);
+        assertEquals(1, list.size());
+        assertArrayEquals(arr, list.get(0));
+    }
+
+}

core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/language/collections/MapFactoryMethodsUnitTest.java

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+package com.baeldung.java9.language.collections;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+public class MapFactoryMethodsUnitTest {
+
+    @Test
+    public void whenMapCreated_thenSuccess() {
+        Map<String, String> traditionlMap = new HashMap<String, String>();
+        traditionlMap.put("foo", "a");
+        traditionlMap.put("bar", "b");
+        traditionlMap.put("baz", "c");
+        Map<String, String> factoryCreatedMap = Map.of("foo", "a", "bar", "b", "baz", "c");
+        assertEquals(traditionlMap, factoryCreatedMap);
+    }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public void onElemAdd_ifUnSupportedOpExpnThrown_thenSuccess() {
+        Map<String, String> map = Map.of("foo", "a", "bar", "b");
+        map.put("baz", "c");
+    }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public void onElemModify_ifUnSupportedOpExpnThrown_thenSuccess() {
+        Map<String, String> map = Map.of("foo", "a", "bar", "b");
+        map.put("foo", "c");
+    }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public void onElemRemove_ifUnSupportedOpExpnThrown_thenSuccess() {
+        Map<String, String> map = Map.of("foo", "a", "bar", "b");
+        map.remove("foo");
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void givenDuplicateKeys_ifIllegalArgExp_thenSuccess() {
+        Map.of("foo", "a", "foo", "b");
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void onNullKey_ifNullPtrExp_thenSuccess() {
+        Map.of("foo", "a", null, "b");
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void onNullValue_ifNullPtrExp_thenSuccess() {
+        Map.of("foo", "a", "bar", null);
+    }
+
+    @Test
+    public void ifNotHashMap_thenSuccess() {
+        Map<String, String> map = Map.of("foo", "a", "bar", "b");
+        assertFalse(map instanceof HashMap);
+    }
+
+}

core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/language/collections/SetFactoryMethodsUnitTest.java

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+package com.baeldung.java9.language.collections;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+public class SetFactoryMethodsUnitTest {
+
+    @Test
+    public void whenSetCreated_thenSuccess() {
+        Set<String> traditionlSet = new HashSet<String>();
+        traditionlSet.add("foo");
+        traditionlSet.add("bar");
+        traditionlSet.add("baz");
+        Set<String> factoryCreatedSet = Set.of("foo", "bar", "baz");
+        assertEquals(traditionlSet, factoryCreatedSet);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void onDuplicateElem_IfIllegalArgExp_thenSuccess() {
+        Set.of("foo", "bar", "baz", "foo");
+    }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public void onElemAdd_ifUnSupportedOpExpnThrown_thenSuccess() {
+        Set<String> set = Set.of("foo", "bar");
+        set.add("baz");
+    }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public void onElemRemove_ifUnSupportedOpExpnThrown_thenSuccess() {
+        Set<String> set = Set.of("foo", "bar", "baz");
+        set.remove("foo");
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void onNullElem_ifNullPtrExpnThrown_thenSuccess() {
+        Set.of("foo", "bar", null);
+    }
+
+    @Test
+    public void ifNotHashSet_thenSuccess() {
+        Set<String> list = Set.of("foo", "bar");
+        assertFalse(list instanceof HashSet);
+    }
+
+    @Test
+    public void ifSetSizeIsOne_thenSuccess() {
+        int[] arr = { 1, 2, 3, 4 };
+        Set<int[]> set = Set.of(arr);
+        assertEquals(1, set.size());
+        assertArrayEquals(arr, set.iterator().next());
+    }
+
+}

core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/language/stream/CollectorImprovementUnitTest.java

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+package com.baeldung.java9.language.stream;
+
+import org.junit.Test;
+
+import java.util.*;
+import java.util.stream.Collectors;
+import java.util.function.Function;
+
+import static org.junit.Assert.assertEquals;
+
+public class CollectorImprovementUnitTest {
+    @Test
+    public void givenList_whenSatifyPredicate_thenMapValueWithOccurences() {
+        List<Integer> numbers = List.of(1, 2, 3, 5, 5);
+
+        Map<Integer, Long> result = numbers.stream().filter(val -> val > 3).collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
+
+        assertEquals(1, result.size());
+
+        result = numbers.stream().collect(Collectors.groupingBy(Function.identity(), Collectors.filtering(val -> val > 3, Collectors.counting())));
+
+        assertEquals(4, result.size());
+    }
+
+    @Test
+    public void givenListOfBlogs_whenAuthorName_thenMapAuthorWithComments() {
+        Blog blog1 = new Blog("1", "Nice", "Very Nice");
+        Blog blog2 = new Blog("2", "Disappointing", "Ok", "Could be better");
+        List<Blog> blogs = List.of(blog1, blog2);
+
+        Map<String, List<List<String>>> authorComments1 = blogs.stream().collect(Collectors.groupingBy(Blog::getAuthorName, Collectors.mapping(Blog::getComments, Collectors.toList())));
+
+        assertEquals(2, authorComments1.size());
+        assertEquals(2, authorComments1.get("1").get(0).size());
+        assertEquals(3, authorComments1.get("2").get(0).size());
+
+        Map<String, List<String>> authorComments2 = blogs.stream().collect(Collectors.groupingBy(Blog::getAuthorName, Collectors.flatMapping(blog -> blog.getComments().stream(), Collectors.toList())));
+
+        assertEquals(2, authorComments2.size());
+        assertEquals(2, authorComments2.get("1").size());
+        assertEquals(3, authorComments2.get("2").size());
+    }
+}
+
+class Blog {
+    private String authorName;
+    private List<String> comments;
+
+    public Blog(String authorName, String... comments) {
+        this.authorName = authorName;
+        this.comments = List.of(comments);
+    }
+
+    public String getAuthorName() {
+        return this.authorName;
+    }
+
+    public List<String> getComments() {
+        return this.comments;
+    }
+}

core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/language/stream/StreamFeaturesUnitTest.java

@@ -0,0 +1,111 @@
+package com.baeldung.java9.language.stream;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static java.lang.Integer.*;
+import static org.junit.Assert.assertEquals;
+
+public class StreamFeaturesUnitTest {
+
+    public static class TakeAndDropWhileTest {
+
+        public Stream<String> getStreamAfterTakeWhileOperation() {
+            return Stream.iterate("", s -> s + "s").takeWhile(s -> s.length() < 10);
+        }
+
+        public Stream<String> getStreamAfterDropWhileOperation() {
+            return Stream.iterate("", s -> s + "s").takeWhile(s -> s.length() < 10).dropWhile(s -> !s.contains("sssss"));
+        }
+
+        @Test
+        public void testTakeWhileOperation() {
+            List<String> list = getStreamAfterTakeWhileOperation().collect(Collectors.toList());
+
+            assertEquals(10, list.size());
+
+            assertEquals("", list.get(0));
+            assertEquals("ss", list.get(2));
+            assertEquals("sssssssss", list.get(list.size() - 1));
+        }
+
+        @Test
+        public void testDropWhileOperation() {
+            List<String> list = getStreamAfterDropWhileOperation().collect(Collectors.toList());
+
+            assertEquals(5, list.size());
+
+            assertEquals("sssss", list.get(0));
+            assertEquals("sssssss", list.get(2));
+            assertEquals("sssssssss", list.get(list.size() - 1));
+        }
+
+    }
+
+    public static class IterateTest {
+
+        private Stream<Integer> getStream() {
+            return Stream.iterate(0, i -> i < 10, i -> i + 1);
+        }
+
+        @Test
+        public void testIterateOperation() {
+            List<Integer> list = getStream().collect(Collectors.toList());
+
+            assertEquals(10, list.size());
+
+            assertEquals(valueOf(0), list.get(0));
+            assertEquals(valueOf(5), list.get(5));
+            assertEquals(valueOf(9), list.get(list.size() - 1));
+        }
+
+    }
+
+    public static class OfNullableTest {
+
+        private List<String> collection = Arrays.asList("A", "B", "C");
+        private Map<String, Integer> map = new HashMap<>() {
+            {
+                put("A", 10);
+                put("C", 30);
+            }
+        };
+
+        private Stream<Integer> getStreamWithOfNullable() {
+            return collection.stream().flatMap(s -> Stream.ofNullable(map.get(s)));
+        }
+
+        private Stream<Integer> getStream() {
+            return collection.stream().flatMap(s -> {
+                Integer temp = map.get(s);
+                return temp != null ? Stream.of(temp) : Stream.empty();
+            });
+        }
+
+        private List<Integer> testOfNullableFrom(Stream<Integer> stream) {
+            List<Integer> list = stream.collect(Collectors.toList());
+
+            assertEquals(2, list.size());
+
+            assertEquals(valueOf(10), list.get(0));
+            assertEquals(valueOf(30), list.get(list.size() - 1));
+
+            return list;
+        }
+
+        @Test
+        public void testOfNullable() {
+
+            assertEquals(testOfNullableFrom(getStream()), testOfNullableFrom(getStreamWithOfNullable()));
+
+        }
+
+    }
+
+}