part1 completed

pom.xml

@@ -16,6 +16,15 @@
             <scope>test</scope>
         </dependency>
 
+        <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>1.16.18</version>
+            <scope>provided</scope>
+        </dependency>
+
+
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>

src/main/java/data/Generator.java

@@ -61,6 +61,11 @@ public static Employee generateEmployee() {
 
     public static List<Employee> generateEmployeeList() {
         // TODO
-        throw new UnsupportedOperationException();
+        int maxLength = 10;
+        final int length = ThreadLocalRandom.current().nextInt(maxLength) + 1;
+
+        return Stream.generate(() -> new Employee(generatePerson(), generateJobHistory()))
+                .limit(length)
+                .collect(toList());
     }
 }

src/test/java/part1/exercise/StreamsExercise1.java

@@ -1,6 +1,7 @@
 package part1.exercise;
 
 import data.Employee;
+import data.Generator;
 import data.JobHistoryEntry;
 import data.Person;
 import org.junit.Test;
@@ -12,9 +13,9 @@
 import java.util.stream.Stream;
 
 import static data.Generator.generateEmployeeList;
-import static java.util.stream.Collectors.groupingBy;
-import static java.util.stream.Collectors.mapping;
-import static java.util.stream.Collectors.toList;
+import static java.util.stream.Collectors.*;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
 
 public class StreamsExercise1 {
     // https://youtu.be/kxgo7Y4cdA8 Сергей Куксенко и Алексей Шипилёв — Через тернии к лямбдам, часть 1
@@ -25,14 +26,30 @@ public class StreamsExercise1 {
 
     @Test
     public void getAllEpamEmployees() {
-        List<Person> epamEmployees = null;// TODO all persons with experience in epam
-        throw new UnsupportedOperationException();
+        // TODO all persons with experience in epam
+        final List<Employee> employees = Generator.generateEmployeeList();
+        List<Person> epamEmployees = employees.stream()
+                .filter(e -> e.getJobHistory().stream().anyMatch(j -> j.getPosition().equals("epam")))
+                .map(Employee::getPerson)
+                .collect(Collectors.toList());
+
+        assertTrue(epamEmployees.stream()
+                .allMatch(p -> employees.stream().anyMatch(e ->
+                        e.getPerson().equals(p) && e.getJobHistory().stream().anyMatch(j -> j.getPosition().equals("epam")))));
     }
 
     @Test
     public void getEmployeesStartedFromEpam() {
-        List<Person> epamEmployees = null;// TODO all persons with first experience in epam
-        throw new UnsupportedOperationException();
+        // TODO all persons with first experience in epam
+        final List<Employee> employees = Generator.generateEmployeeList();
+        List<Person> epamEmployees = employees.stream()
+                .filter(e -> e.getJobHistory().get(0).getPosition().equals("epam"))
+                .map(Employee::getPerson)
+                .collect(Collectors.toList());
+
+        assertTrue(epamEmployees.stream()
+                .allMatch(p -> employees.stream().anyMatch(e ->
+                        e.getPerson().equals(p) && e.getJobHistory().get(0).getPosition().equals("epam"))));
     }
 
     @Test
@@ -50,10 +67,13 @@ public void sumEpamDurations() {
         }
 
         // TODO
-        throw new UnsupportedOperationException();
+        int actual = employees.stream()
+                .flatMap(e -> e.getJobHistory().stream())
+                .filter(j -> j.getEmployer().equals("epam"))
+                .mapToInt(JobHistoryEntry::getDuration)
+                .sum();
 
-        // int result = ???
-        // assertEquals(expected, result);
+        assertEquals(expected, actual);
     }
 
 }

src/test/java/part1/exercise/StreamsExercise2.java

@@ -3,17 +3,16 @@
 import data.Employee;
 import data.JobHistoryEntry;
 import data.Person;
+import lombok.AllArgsConstructor;
+import lombok.Data;
 import org.junit.Test;
 
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.List;
-import java.util.Map;
-import java.util.stream.Stream;
+import java.util.*;
 
-import static data.Generator.generateEmployeeList;
 import static java.util.stream.Collectors.*;
+import static org.hamcrest.CoreMatchers.is;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
 
 public class StreamsExercise2 {
     // https://youtu.be/kxgo7Y4cdA8 Сергей Куксенко и Алексей Шипилёв — Через тернии к лямбдам, часть 1
@@ -24,21 +23,81 @@ public class StreamsExercise2 {
 
     // TODO class PersonEmployerPair
 
+    @Data
+    @AllArgsConstructor
+    private static class Pair<F, S> {
+        private F first;
+        private S second;
+    }
+
     @Test
     public void employersStuffLists() {
-        Map<String, List<Person>> employersStuffLists = null;// TODO
-        throw new UnsupportedOperationException();
+        Map<String, List<Person>> expected = new HashMap<>();
+        for (Employee e : getEmployees()){
+            e.getJobHistory().forEach(j -> {
+                final String employer = j.getEmployer();
+                if (expected.containsKey(employer))
+                    expected.get(employer).add(e.getPerson());
+                else {
+                    List<Person> list = new ArrayList<>();
+                    list.add(e.getPerson());
+                    expected.put(employer, list);
+                }
+            });
+        }
+
+        // TODO
+        Map<String, List<Person>> actual = getEmployees().stream()
+                .flatMap(e -> e.getJobHistory().stream()
+                                    .map(j -> new Pair<>(j.getEmployer(), e.getPerson())))
+                .collect(groupingBy(
+                        Pair::getFirst,
+                        mapping(Pair::getSecond, toList())
+                ));
+        assertThat(actual, is(expected));
     }
 
     @Test
     public void indexByFirstEmployer() {
-        Map<String, List<Person>> employeesIndex = null;// TODO
-        throw new UnsupportedOperationException();
+        Map<String, List<Person>> expected = new HashMap<>();
+        for (Employee e : getEmployees()){
+            if (e.getJobHistory().size() > 0) {
+                final String firstEmployer = e.getJobHistory().get(0).getEmployer();
+                if (expected.containsKey(firstEmployer))
+                    expected.get(firstEmployer).add(e.getPerson());
+                else {
+                    List<Person> list = new ArrayList<>();
+                    list.add(e.getPerson());
+                    expected.put(firstEmployer, list);
+                }
+            }
+        }
+
+        // TODO
+        Map<String, List<Person>> actual = getEmployees().stream()
+                .flatMap(e -> e.getJobHistory().stream().limit(1)
+                        .map(j -> new Pair<>(j.getEmployer(), e.getPerson())))
+                .collect(groupingBy(
+                        Pair::getFirst,
+                        mapping(Pair::getSecond, toList())
+                ));
+        assertThat(actual, is(expected));
     }
 
     @Test
     public void greatestExperiencePerEmployer() {
-        Map<String, Person> employeesIndex = null;// TODO
+        // TODO
+        Map<String, Person> employeesIndex = getEmployees().stream()
+                .flatMap(e -> e.getJobHistory().stream().limit(1)
+                        .map(j -> new Pair<>(new Pair<>(j.getEmployer(), e.getPerson()), j.getDuration())))
+                .collect(
+                        groupingBy(
+                            t -> t.getFirst().getFirst(),
+                            collectingAndThen(
+                                    maxBy(Comparator.comparingInt(Pair::getSecond)),
+                                    p -> p.get().getFirst().getSecond()
+                            )
+                ));
 
         assertEquals(new Person("John", "White", 28), employeesIndex.get("epam"));
     }