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

core-java-modules/core-java-9-new-features/compile-modules.sh

@@ -0,0 +1 @@
+javac -d mods --module-source-path src/modules $(find src/modules -name "*.java")

core-java-modules/core-java-9-new-features/logging.sh

@@ -0,0 +1,15 @@
+# compile logging  module
+# javac --module-path mods -d mods/com.baeldung.logging src/modules/com.baeldung.logging/module-info.java src/modules/com.baeldung.logging/com/baeldung/logging/*.java
+
+# compile logging slf4j module
+javac --module-path mods -d mods/com.baeldung.logging.slf4j src/modules/com.baeldung.logging.slf4j/module-info.java src/modules/com.baeldung.logging.slf4j/com/baeldung/logging/slf4j/*.java
+
+
+# compile logging main app module
+javac --module-path mods -d mods/com.baeldung.logging.app src/modules/com.baeldung.logging.app/module-info.java src/modules/com.baeldung.logging.app/com/baeldung/logging/app/*.java
+
+# run logging main app
+# java --module-path mods -m com.baeldung.logging.app/com.baeldung.logging.app.MainApp
+
+# run looging main app using logback
+java --module-path mods -Dlogback.configurationFile=mods/logback.xml -m com.baeldung.logging.app/com.baeldung.logging.app.MainApp

core-java-modules/core-java-9-new-features/mods/logback.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
+            <pattern>
+                %d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{36} -- %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root>
+        <appender-ref ref="STDOUT"/>
+    </root>
+
+</configuration>

core-java-modules/core-java-9-new-features/pom.xml

@@ -1,7 +1,7 @@
 <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>
+    <artifactId>core-java-9-new-features</artifactId>
     <version>0.2-SNAPSHOT</version>
     <name>core-java-9</name>
 
@@ -13,23 +13,12 @@
     </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>
@@ -39,7 +28,7 @@
     </dependencies>
 
     <build>
-        <finalName>core-java-9</finalName>
+        <finalName>core-java-9-new-features</finalName>
         <plugins>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
@@ -64,10 +53,8 @@
         <!-- 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-new-features/src/main/java/com/baeldung/java9/language/PrivateInterface.java

@@ -0,0 +1,23 @@
+package com.baeldung.java9.language;
+
+public interface PrivateInterface {
+
+    private static String staticPrivate() {
+        return "static private";
+    }
+
+    private String instancePrivate() {
+        return "instance private";
+    }
+
+    public default void check() {
+        String result = staticPrivate();
+        if (!result.equals("static private"))
+            throw new AssertionError("Incorrect result for static private interface method");
+        PrivateInterface pvt = new PrivateInterface() {
+        };
+        result = pvt.instancePrivate();
+        if (!result.equals("instance private"))
+            throw new AssertionError("Incorrect result for instance private interface method");
+    }
+}

core-java-modules/core-java-9-new-features/src/main/java/com/baeldung/java9/reactive/BaeldungBatchSubscriberImpl.java

@@ -0,0 +1,82 @@
+package com.baeldung.java9.reactive;
+
+import java.util.ArrayList;
+import java.util.concurrent.Flow.Subscriber;
+import java.util.concurrent.Flow.Subscription;
+
+public class BaeldungBatchSubscriberImpl<T> implements Subscriber<String> {
+    private Subscription subscription;
+    private boolean completed = false;
+    private int counter;
+    private ArrayList<String> buffer;
+    public static final int BUFFER_SIZE = 5;
+
+    public BaeldungBatchSubscriberImpl() {
+        buffer = new ArrayList<String>();
+    }
+
+    public boolean isCompleted() {
+        return completed;
+    }
+
+    public void setCompleted(boolean completed) {
+        this.completed = completed;
+    }
+
+    public int getCounter() {
+        return counter;
+    }
+
+    public void setCounter(int counter) {
+        this.counter = counter;
+    }
+
+    @Override
+    public void onSubscribe(Subscription subscription) {
+        this.subscription = subscription;
+        subscription.request(BUFFER_SIZE);
+    }
+
+    @Override
+    public void onNext(String item) {
+        buffer.add(item);
+        // if buffer is full, process the items.
+        if (buffer.size() >= BUFFER_SIZE) {
+            processBuffer();
+        }
+        //request more items.
+        subscription.request(1);
+    }
+
+    private void processBuffer() {
+        if (buffer.isEmpty())
+            return;
+        // Process all items in the buffer. Here, we just print it and sleep for 1 second.
+        System.out.print("Processed items: ");
+        buffer.stream()
+            .forEach(item -> {
+                System.out.print(" " + item);
+            });
+        System.out.println();
+        try {
+            Thread.sleep(1000);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+        counter = counter + buffer.size();
+        buffer.clear();
+    }
+
+    @Override
+    public void onError(Throwable t) {
+        t.printStackTrace();
+    }
+
+    @Override
+    public void onComplete() {
+        completed = true;
+        // process any remaining items in buffer before
+        processBuffer();
+        subscription.cancel();
+    }
+}

core-java-modules/core-java-9-new-features/src/main/java/com/baeldung/java9/reactive/BaeldungSubscriberImpl.java

@@ -0,0 +1,55 @@
+package com.baeldung.java9.reactive;
+
+import java.util.concurrent.Flow.Subscriber;
+import java.util.concurrent.Flow.Subscription;
+
+public class BaeldungSubscriberImpl<T> implements Subscriber<String> {
+    private Subscription subscription;
+    private boolean completed = false;
+    private int counter;
+
+    public boolean isCompleted() {
+        return completed;
+    }
+
+    public void setCompleted(boolean completed) {
+        this.completed = completed;
+    }
+
+    public int getCounter() {
+        return counter;
+    }
+
+    public void setCounter(int counter) {
+        this.counter = counter;
+    }
+
+    @Override
+    public void onSubscribe(Subscription subscription) {
+        this.subscription = subscription;
+        subscription.request(1);
+    }
+
+    @Override
+    public void onNext(String item) {
+        try {
+            Thread.sleep(1000);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+        counter++;
+        System.out.println("Processed item : " + item);
+        subscription.request(1);
+    }
+
+    @Override
+    public void onError(Throwable t) {
+        t.printStackTrace();
+    }
+
+    @Override
+    public void onComplete() {
+        completed = true;
+        subscription.cancel();
+    }
+}

core-java-modules/core-java-9-new-features/src/test/java/com/baeldung/java9/reactive/BaeldungBatchSubscriberImplIntegrationTest.java

@@ -0,0 +1,75 @@
+package com.baeldung.java9.reactive;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.util.concurrent.ForkJoinPool;
+import java.util.concurrent.SubmissionPublisher;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.Stopwatch;
+
+public class BaeldungBatchSubscriberImplIntegrationTest {
+
+    private static final int ITEM_SIZE = 10;
+    private SubmissionPublisher<String> publisher;
+    private BaeldungBatchSubscriberImpl<String> subscriber;
+
+    @Before
+    public void initialize() {
+        this.publisher = new SubmissionPublisher<String>(ForkJoinPool.commonPool(), 6);
+        this.subscriber = new BaeldungBatchSubscriberImpl<String>();
+        publisher.subscribe(subscriber);
+    }
+
+    @Rule
+    public Stopwatch stopwatch = new Stopwatch() {
+
+    };
+
+    @Test
+    public void testReactiveStreamCount() {
+        IntStream.range(0, ITEM_SIZE)
+            .forEach(item -> publisher.submit(item + ""));
+        publisher.close();
+
+        do {
+            // wait for subscribers to complete all processing.
+            try {
+                Thread.sleep(100);
+            } catch (InterruptedException e) {
+                // TODO Auto-generated catch block
+                e.printStackTrace();
+            }
+        } while (!subscriber.isCompleted());
+
+        int count = subscriber.getCounter();
+
+        assertEquals(ITEM_SIZE, count);
+    }
+
+    @Test
+    public void testReactiveStreamTime() {
+        IntStream.range(0, ITEM_SIZE)
+            .forEach(item -> publisher.submit(item + ""));
+        publisher.close();
+
+        do {
+            // wait for subscribers to complete all processing.
+            try {
+                Thread.sleep(100);
+            } catch (InterruptedException e) {
+                // TODO Auto-generated catch block
+                e.printStackTrace();
+            }
+        } while (!subscriber.isCompleted());
+
+        // The runtime in seconds should be equal to the number of items in each batch.
+        assertTrue(stopwatch.runtime(TimeUnit.SECONDS) >= (ITEM_SIZE / subscriber.BUFFER_SIZE));
+    }
+
+}

core-java-modules/core-java-9-new-features/src/test/java/com/baeldung/java9/reactive/BaeldungSubscriberImplIntegrationTest.java

@@ -0,0 +1,100 @@
+package com.baeldung.java9.reactive;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.util.concurrent.ForkJoinPool;
+import java.util.concurrent.SubmissionPublisher;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.Stopwatch;
+
+public class BaeldungSubscriberImplIntegrationTest {
+
+    private static final int ITEM_SIZE = 10;
+    private SubmissionPublisher<String> publisher;
+    private BaeldungSubscriberImpl<String> subscriber;
+
+    @Before
+    public void initialize() {
+        // create Publisher with max buffer capacity 3.
+        this.publisher = new SubmissionPublisher<String>(ForkJoinPool.commonPool(), 3);
+        this.subscriber = new BaeldungSubscriberImpl<String>();
+        publisher.subscribe(subscriber);
+    }
+
+    @Rule
+    public Stopwatch stopwatch = new Stopwatch() {
+
+    };
+
+    @Test
+    public void testReactiveStreamCount() {
+        IntStream.range(0, ITEM_SIZE)
+            .forEach(item -> publisher.submit(item + ""));
+        publisher.close();
+
+        do {
+            // wait for subscribers to complete all processing.
+            try {
+                Thread.sleep(100);
+            } catch (InterruptedException e) {
+                // TODO Auto-generated catch block
+                e.printStackTrace();
+            }
+        } while (!subscriber.isCompleted());
+
+        int count = subscriber.getCounter();
+
+        assertEquals(ITEM_SIZE, count);
+    }
+
+    @Test
+    public void testReactiveStreamTime() {
+        IntStream.range(0, ITEM_SIZE)
+            .forEach(item -> publisher.submit(item + ""));
+        publisher.close();
+
+        do {
+            // wait for subscribers to complete all processing.
+            try {
+                Thread.sleep(100);
+            } catch (InterruptedException e) {
+                // TODO Auto-generated catch block
+                e.printStackTrace();
+            }
+        } while (!subscriber.isCompleted());
+
+        // The runtime in seconds should be equal to the number of items.
+        assertTrue(stopwatch.runtime(TimeUnit.SECONDS) >= ITEM_SIZE);
+    }
+
+    @Test
+    public void testReactiveStreamOffer() {
+        IntStream.range(0, ITEM_SIZE)
+            .forEach(item -> publisher.offer(item + "", (subscriber, string) -> {
+                // Returning false means this item will be dropped (no retry), if blocked.
+                return false;
+            }));
+        publisher.close();
+
+        do {
+            // wait for subscribers to complete all processing.
+            try {
+                Thread.sleep(100);
+            } catch (InterruptedException e) {
+                // TODO Auto-generated catch block
+                e.printStackTrace();
+            }
+        } while (!subscriber.isCompleted());
+
+        int count = subscriber.getCounter();
+        // Because 10 items were offered and the buffer capacity was 3, few items will not be processed.
+        assertTrue(ITEM_SIZE > count);
+    }
+
+}

core-java-modules/core-java-9-new-features/src/test/java/com/baeldung/java9/stackwalker/StackWalkerDemoUnitTest.java

@@ -0,0 +1,16 @@
+package com.baeldung.java9.stackwalker;
+
+import org.junit.Test;
+
+public class StackWalkerDemoUnitTest {
+
+    @Test
+    public void giveStalkWalker_whenWalkingTheStack_thenShowStackFrames() {
+        new StackWalkerDemo().methodOne();
+    }
+    
+    @Test
+    public void giveStalkWalker_whenInvokingFindCaller_thenFindCallingClass() {
+        new StackWalkerDemo().findCaller();
+    }
+}

core-java-modules/core-java-9-new-features/src/test/java/com/baeldung/java9/streams.reactive/ReactiveStreamsTest.java

@@ -0,0 +1,73 @@
+package com.baeldung.java9.streams.reactive;
+
+
+import org.junit.Test;
+
+import java.util.List;
+import java.util.concurrent.SubmissionPublisher;
+
+import static org.assertj.core.api.Java6Assertions.assertThat;
+
+public class ReactiveStreamsTest {
+
+    @Test
+    public void givenPublisher_whenSubscribeToIt_thenShouldConsumeAllElements() throws InterruptedException {
+        //given
+        SubmissionPublisher<String> publisher = new SubmissionPublisher<>();
+        EndSubscriber<String> subscriber = new EndSubscriber<>(6);
+        publisher.subscribe(subscriber);
+        List<String> items = List.of("1", "x", "2", "x", "3", "x");
+
+        //when
+        assertThat(publisher.getNumberOfSubscribers()).isEqualTo(1);
+        items.forEach(publisher::submit);
+        publisher.close();
+
+        //then
+
+        await().atMost(1000, TimeUnit.MILLISECONDS).until(
+                () -> assertThat(subscriber.consumedElements).containsExactlyElementsOf(items)
+        );
+    }
+
+    @Test
+    public void givenPublisher_whenSubscribeAndTransformElements_thenShouldConsumeAllElements() throws InterruptedException {
+        //given
+        SubmissionPublisher<String> publisher = new SubmissionPublisher<>();
+        TransformProcessor<String, Integer> transformProcessor = new TransformProcessor<>(Integer::parseInt);
+        EndSubscriber<Integer> subscriber = new EndSubscriber<>(3);
+        List<String> items = List.of("1", "2", "3");
+        List<Integer> expectedResult = List.of(1, 2, 3);
+
+        //when
+        publisher.subscribe(transformProcessor);
+        transformProcessor.subscribe(subscriber);
+        items.forEach(publisher::submit);
+        publisher.close();
+
+        //then
+        await().atMost(1000, TimeUnit.MILLISECONDS).until(
+                () -> assertThat(subscriber.consumedElements).containsExactlyElementsOf(expectedResult)
+        );
+    }
+
+    @Test
+    public void givenPublisher_whenRequestForOnlyOneElement_thenShouldConsumeOnlyThatOne() throws InterruptedException {
+        //given
+        SubmissionPublisher<String> publisher = new SubmissionPublisher<>();
+        EndSubscriber<String> subscriber = new EndSubscriber<>(1);
+        publisher.subscribe(subscriber);
+        List<String> items = List.of("1", "x", "2", "x", "3", "x");
+        List<String> expected = List.of("1");
+
+        //when
+        assertThat(publisher.getNumberOfSubscribers()).isEqualTo(1);
+        items.forEach(publisher::submit);
+        publisher.close();
+
+        //then
+        await().atMost(1000, TimeUnit.MILLISECONDS).until(
+                () -> assertThat(subscriber.consumedElements).containsExactlyElementsOf(expected)
+        );
+    }
+}