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Streams completed #57

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7 changes: 5 additions & 2 deletions src/main/java/data/Generator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,10 @@ public static Employee generateEmployee() {
}

public static List<Employee> generateEmployeeList() {
// TODO
throw new UnsupportedOperationException();
final int maxLength = 10;
final int length = ThreadLocalRandom.current().nextInt(maxLength) + 1;
return Stream.generate(Generator::generateEmployee)
.limit(length)
.collect(toList());
}
}
56 changes: 43 additions & 13 deletions src/test/java/part1/exercise/StreamsExercise1.java
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Original file line number Diff line number Diff line change
Expand Up @@ -6,15 +6,12 @@
import org.junit.Test;

import java.util.*;
import java.util.concurrent.ThreadLocalRandom;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
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.summingInt;
import static java.util.stream.Collectors.toList;
import static org.junit.Assert.assertEquals;

public class StreamsExercise1 {
// https://youtu.be/kxgo7Y4cdA8 Сергей Куксенко и Алексей Шипилёв — Через тернии к лямбдам, часть 1
Expand All @@ -25,14 +22,45 @@ public class StreamsExercise1 {

@Test
public void getAllEpamEmployees() {
List<Person> epamEmployees = null;// TODO all persons with experience in epam
throw new UnsupportedOperationException();
List<Employee> employees = generateEmployeeList();

List<Person> personsList = employees.stream()
.filter(e -> e.getJobHistory().stream()
.map(JobHistoryEntry::getEmployer)
.anyMatch(em -> em.equals("epam")))
.map(Employee::getPerson)
.collect(toList());

List<Person> expectedPersonList = new ArrayList<>();
for (Employee e : employees) {
for (JobHistoryEntry j : e.getJobHistory()) {
if (j.getEmployer().equals("epam")) {
expectedPersonList.add(e.getPerson());
break;
}
}
}

assertEquals(expectedPersonList, personsList);
}

@Test
public void getEmployeesStartedFromEpam() {
List<Person> epamEmployees = null;// TODO all persons with first experience in epam
throw new UnsupportedOperationException();
List<Employee> employees = generateEmployeeList();

List<Person> personList = employees.stream()
.filter(e -> e.getJobHistory().get(0).getEmployer().equals("epam"))
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Don't use get - it fails on empty collection.

.map(Employee::getPerson)
.collect(toList());

List<Person> epamEmployeesExpected = new ArrayList<>();
for (Employee e : employees) {
if (e.getJobHistory().get(0).getEmployer().equals("epam")) {
epamEmployeesExpected.add(e.getPerson());
}
}

assertEquals(epamEmployeesExpected, personList);
}

@Test
Expand All @@ -49,11 +77,13 @@ public void sumEpamDurations() {
}
}

// TODO
throw new UnsupportedOperationException();
int result = employees.stream()
.flatMap(e -> e.getJobHistory().stream())
.filter(j -> j.getEmployer().equals("epam"))
.mapToInt(JobHistoryEntry::getDuration)
.sum();

// int result = ???
// assertEquals(expected, result);
assertEquals(expected, result);
}

}
223 changes: 145 additions & 78 deletions src/test/java/part1/exercise/StreamsExercise2.java
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Original file line number Diff line number Diff line change
Expand Up @@ -5,10 +5,14 @@
import data.Person;
import org.junit.Test;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import static data.Generator.generateEmployeeList;
Expand All @@ -22,102 +26,165 @@ public class StreamsExercise2 {
// https://youtu.be/O8oN4KSZEXE Сергей Куксенко — Stream API, часть 1
// https://youtu.be/i0Jr2l3jrDA Сергей Куксенко — Stream API, часть 2

// TODO class PersonEmployerPair
private static class PersonEmployerPair {

private final Person person;
private final String employer;
private final int duration;

private PersonEmployerPair(Person person, String employer, int duration) {
this.person = person;
this.employer = employer;
this.duration = duration;
}

public Person getPerson() {
return person;
}

public String getEmployer() {
return employer;
}

public int getDuration() {
return duration;
}
}

@Test
public void employersStuffLists() {
Map<String, List<Person>> employersStuffLists = null;// TODO
throw new UnsupportedOperationException();
Map<String, List<Person>> employersStuffLists = getEmployees().stream()
.flatMap(employee -> employee.getJobHistory().stream()
.map(j -> new PersonEmployerPair(employee.getPerson(), j.getEmployer(), j.getDuration())))
.collect(Collectors.groupingBy(
PersonEmployerPair::getEmployer,
mapping(PersonEmployerPair::getPerson, toList())
));

List<Person> personList = new ArrayList<>();
personList.add(new Person("John", "Doe", 21));
personList.add(new Person("John", "Doe", 24));
personList.add(new Person("Bob", "Doe", 27));
personList.add(new Person("John", "Doe", 30));

assertEquals(personList, employersStuffLists.get("abc"));
}

@Test
public void indexByFirstEmployer() {
Map<String, List<Person>> employeesIndex = null;// TODO
throw new UnsupportedOperationException();
Map<String, List<Person>> employeesIndex = getEmployees().stream()
.map(employee -> new PersonEmployerPair(employee.getPerson(),
employee.getJobHistory().get(0).getEmployer(),
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Avoid get.

employee.getJobHistory().get(0).getDuration()))
.collect(Collectors.groupingBy(
PersonEmployerPair::getEmployer,
mapping(PersonEmployerPair::getPerson, toList())
));

List<Person> personList = new ArrayList<>();
personList.add(new Person("John", "Galt", 20));
personList.add(new Person("John", "White", 22));
personList.add(new Person("John", "Galt", 23));
personList.add(new Person("John", "White", 25));
personList.add(new Person("John", "Galt", 26));
personList.add(new Person("John", "White", 28));
personList.add(new Person("John", "Galt", 29));
personList.add(new Person("Bob", "White", 31));

assertEquals(personList, employeesIndex.get("epam"));

}

@Test
public void greatestExperiencePerEmployer() {
Map<String, Person> employeesIndex = null;// TODO
Map<String, Person> employeesIndex = getEmployees().stream()
.flatMap(employee -> employee.getJobHistory().stream()
.map(j -> new PersonEmployerPair(employee.getPerson(), j.getEmployer(), j.getDuration())))
.collect(Collectors.groupingBy(
PersonEmployerPair::getEmployer,
Collectors.collectingAndThen(
Collectors.maxBy(Comparator.comparingInt(PersonEmployerPair::getDuration)),
p -> p.get().getPerson())
));

assertEquals(new Person("John", "White", 28), employeesIndex.get("epam"));
}


private List<Employee> getEmployees() {
return Arrays.asList(
new Employee(
new Person("John", "Galt", 20),
Arrays.asList(
new JobHistoryEntry(3, "dev", "epam"),
new JobHistoryEntry(2, "dev", "google")
)),
new Employee(
new Person("John", "Doe", 21),
Arrays.asList(
new JobHistoryEntry(4, "BA", "yandex"),
new JobHistoryEntry(2, "QA", "epam"),
new JobHistoryEntry(2, "dev", "abc")
)),
new Employee(
new Person("John", "White", 22),
Collections.singletonList(
new JobHistoryEntry(6, "QA", "epam")
)),
new Employee(
new Person("John", "Galt", 23),
Arrays.asList(
new JobHistoryEntry(3, "dev", "epam"),
new JobHistoryEntry(2, "dev", "google")
)),
new Employee(
new Person("John", "Doe", 24),
Arrays.asList(
new JobHistoryEntry(4, "QA", "yandex"),
new JobHistoryEntry(2, "BA", "epam"),
new JobHistoryEntry(2, "dev", "abc")
)),
new Employee(
new Person("John", "White", 25),
Collections.singletonList(
new JobHistoryEntry(6, "QA", "epam")
)),
new Employee(
new Person("John", "Galt", 26),
Arrays.asList(
new JobHistoryEntry(3, "dev", "epam"),
new JobHistoryEntry(1, "dev", "google")
)),
new Employee(
new Person("Bob", "Doe", 27),
Arrays.asList(
new JobHistoryEntry(4, "QA", "yandex"),
new JobHistoryEntry(2, "QA", "epam"),
new JobHistoryEntry(2, "dev", "abc")
)),
new Employee(
new Person("John", "White", 28),
Collections.singletonList(
new JobHistoryEntry(666, "BA", "epam")
)),
new Employee(
new Person("John", "Galt", 29),
Arrays.asList(
new JobHistoryEntry(3, "dev", "epam"),
new JobHistoryEntry(1, "dev", "google")
)),
new Employee(
new Person("John", "Doe", 30),
Arrays.asList(
new JobHistoryEntry(4, "QA", "yandex"),
new JobHistoryEntry(2, "QA", "epam"),
new JobHistoryEntry(5, "dev", "abc")
)),
new Employee(
new Person("Bob", "White", 31),
Collections.singletonList(
new JobHistoryEntry(6, "QA", "epam")
))
new Employee(
new Person("John", "Galt", 20),
Arrays.asList(
new JobHistoryEntry(3, "dev", "epam"),
new JobHistoryEntry(2, "dev", "google")
)),
new Employee(
new Person("John", "Doe", 21),
Arrays.asList(
new JobHistoryEntry(4, "BA", "yandex"),
new JobHistoryEntry(2, "QA", "epam"),
new JobHistoryEntry(2, "dev", "abc")
)),
new Employee(
new Person("John", "White", 22),
Collections.singletonList(
new JobHistoryEntry(6, "QA", "epam")
)),
new Employee(
new Person("John", "Galt", 23),
Arrays.asList(
new JobHistoryEntry(3, "dev", "epam"),
new JobHistoryEntry(2, "dev", "google")
)),
new Employee(
new Person("John", "Doe", 24),
Arrays.asList(
new JobHistoryEntry(4, "QA", "yandex"),
new JobHistoryEntry(2, "BA", "epam"),
new JobHistoryEntry(2, "dev", "abc")
)),
new Employee(
new Person("John", "White", 25),
Collections.singletonList(
new JobHistoryEntry(6, "QA", "epam")
)),
new Employee(
new Person("John", "Galt", 26),
Arrays.asList(
new JobHistoryEntry(3, "dev", "epam"),
new JobHistoryEntry(1, "dev", "google")
)),
new Employee(
new Person("Bob", "Doe", 27),
Arrays.asList(
new JobHistoryEntry(4, "QA", "yandex"),
new JobHistoryEntry(2, "QA", "epam"),
new JobHistoryEntry(2, "dev", "abc")
)),
new Employee(
new Person("John", "White", 28),
Collections.singletonList(
new JobHistoryEntry(666, "BA", "epam")
)),
new Employee(
new Person("John", "Galt", 29),
Arrays.asList(
new JobHistoryEntry(3, "dev", "epam"),
new JobHistoryEntry(1, "dev", "google")
)),
new Employee(
new Person("John", "Doe", 30),
Arrays.asList(
new JobHistoryEntry(4, "QA", "yandex"),
new JobHistoryEntry(2, "QA", "epam"),
new JobHistoryEntry(5, "dev", "abc")
)),
new Employee(
new Person("Bob", "White", 31),
Collections.singletonList(
new JobHistoryEntry(6, "QA", "epam")
))
);
}

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