map vs flatMap

java-8/java-map-flatmap/pom.xml

@@ -0,0 +1,75 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<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.javadevjournal</groupId>
+  <artifactId>java-map-flatmap</artifactId>
+  <version>1.0-SNAPSHOT</version>
+
+  <name>java-map-flatmap</name>
+  <!-- FIXME change it to the project's website -->
+  <url>http://www.example.com</url>
+
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <maven.compiler.source>1.8</maven.compiler.source>
+    <maven.compiler.target>1.8</maven.compiler.target>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>4.11</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
+      <plugins>
+        <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
+        <plugin>
+          <artifactId>maven-clean-plugin</artifactId>
+          <version>3.1.0</version>
+        </plugin>
+        <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
+        <plugin>
+          <artifactId>maven-resources-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-compiler-plugin</artifactId>
+          <version>3.8.0</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-surefire-plugin</artifactId>
+          <version>2.22.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-jar-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-install-plugin</artifactId>
+          <version>2.5.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-deploy-plugin</artifactId>
+          <version>2.8.2</version>
+        </plugin>
+        <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
+        <plugin>
+          <artifactId>maven-site-plugin</artifactId>
+          <version>3.7.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-project-info-reports-plugin</artifactId>
+          <version>3.0.0</version>
+        </plugin>
+      </plugins>
+    </pluginManagement>
+  </build>
+</project>

java-8/java-map-flatmap/src/main/java/com/javadevjournal/App.java

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+package com.javadevjournal;
+
+/**
+ * Hello world!
+ *
+ */
+public class App 
+{
+    public static void main( String[] args )
+    {
+        System.out.println( "Hello World!" );
+    }
+}

java-8/java-map-flatmap/src/main/java/com/javadevjournal/FlatMapExample.java

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+package com.javadevjournal;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class FlatMapExample {
+
+    public static void main(String[] args) {
+
+        List<String> words= Arrays.asList("JavaDevJournal","Java");
+        List<String> unique=  words.stream()
+               .map( s-> s.split(""))
+               .flatMap(Arrays::stream)
+               .distinct()
+               .collect(Collectors.toList());
+
+       unique.forEach(System.out::println);
+    }
+}

java-8/java-map-flatmap/src/main/java/com/javadevjournal/MapExample.java

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+package com.javadevjournal;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class MapExample {
+
+    public static void main(String[] args) {
+        List<String> words= Arrays.asList("Java Dev Journal","Java", "Spring Boot","Java 8");
+
+        List<Integer> wordCount = words.stream()
+                        .map(String::length)
+                        .collect(Collectors.toList());
+
+        wordCount.forEach(System.out::println);
+    }
+}

java-8/java-map-flatmap/src/test/java/com/javadevjournal/AppTest.java

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+package com.javadevjournal;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+/**
+ * Unit test for simple App.
+ */
+public class AppTest 
+{
+    /**
+     * Rigorous Test :-)
+     */
+    @Test
+    public void shouldAnswerWithTrue()
+    {
+        assertTrue( true );
+    }
+}