stream.homework module

kodilla-stream/src/main/java/com/kodilla/optional/homework/Application.java

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+package com.kodilla.optional.homework;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
+
+public class Application {
+    public static void main(String[] args) {
+        List<Student> students = new ArrayList<>(Arrays.asList(
+            new Student("Scout Duke", new Teacher("Martha Nguyen")),
+            new Student("Paola Rice", null),
+            new Student("Laurel Reilly", new Teacher("Brooklyn Hopkins"))
+        ));
+
+        for (Student student : students) {
+            System.out.println(
+                "student: "
+                    + student.getName()
+                    + " - teacher: "
+                    + Optional.ofNullable(student.getTeacher()).orElse(new Teacher("<undefined>")).getName()
+            );
+        }
+    }
+}

kodilla-stream/src/main/java/com/kodilla/optional/homework/Student.java

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+package com.kodilla.optional.homework;
+
+public class Student {
+    private String name;
+    private Teacher teacher;
+
+    public Student(String name, Teacher teacher) {
+        this.name = name;
+        this.teacher = teacher;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public Teacher getTeacher() {
+        return teacher;
+    }
+}

kodilla-stream/src/main/java/com/kodilla/optional/homework/Teacher.java

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+package com.kodilla.optional.homework;
+
+public class Teacher {
+    private String name;
+
+    public Teacher(String name) {
+        this.name = name;
+    }
+
+    public String getName() {
+        return name;
+    }
+}

kodilla-stream/src/main/java/com/kodilla/stream/homework/ForumStats.java

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+package com.kodilla.stream.homework;
+
+import com.kodilla.stream.User;
+import com.kodilla.stream.UsersRepository;
+
+import java.util.List;
+
+public class ForumStats {
+    public static double getAverageNumberOfPostsForOldUsers(List<User> users) {
+        return users
+            .stream()
+            .filter(user -> user.getAge() >= 40)
+            .mapToInt(user -> user.getNumberOfPost())
+            .average()
+            .orElse(-1);
+    }
+
+    public static double getAverageNumberOfPostsForYoungUsers(List<User> users) {
+        return users
+            .stream()
+            .filter(user -> user.getAge() < 40)
+            .mapToInt(user -> user.getNumberOfPost())
+            .average()
+            .orElse(-1);
+    }
+
+    public static void main(String[] args) {
+        System.out.println("old users (>=40): " + getAverageNumberOfPostsForOldUsers(UsersRepository.getUsersList()));
+        System.out.println("young users (<40): " + getAverageNumberOfPostsForYoungUsers(UsersRepository.getUsersList()));
+    }
+}

kodilla-stream/src/test/java/com/kodilla/optional/ApplicationTest.java

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+package com.kodilla.optional;
+
+import org.junit.jupiter.api.Test;
+
+public class ApplicationTest {
+
+    @Test
+    public void testCokolwiek() {
+
+    }
+}

kodilla-stream/src/test/java/com/kodilla/stream/homework/ForumStatsTestSuite.java

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+package com.kodilla.stream.homework;
+
+import com.kodilla.stream.User;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class ForumStatsTestSuite {
+    @Test
+    public void testGetAverageNumberOfPostsForOldUsers() {
+        List<User> users = new ArrayList<>(Arrays.asList(
+            new User("Khalil Bridges", 31, 215, "A"),
+            new User("Thiago Shepherd", 17, 385, "B"),
+            new User("Kasen Rasmussen", 58, 2, "C"),
+            new User("Emery McKenzie", 47, 98, "A")
+        ));
+
+        assertEquals(50., ForumStats.getAverageNumberOfPostsForOldUsers(users), 0.001);
+    }
+
+    @Test
+    public void testGetAverageNumberOfPostsForNewUsers() {
+        List<User> users = new ArrayList<>(Arrays.asList(
+                new User("Khalil Bridges", 31, 215, "A"),
+                new User("Thiago Shepherd", 17, 385, "B"),
+                new User("Kasen Rasmussen", 58, 2, "C"),
+                new User("Emery McKenzie", 47, 98, "A")
+        ));
+
+        assertEquals(300., ForumStats.getAverageNumberOfPostsForYoungUsers(users), 0.001);
+    }
+}