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224 changes: 220 additions & 4 deletions src/test/java/lambda/part3/exercise/FilterMap.java
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Original file line number Diff line number Diff line change
@@ -1,10 +1,22 @@
package lambda.part3.exercise;

import data.Employee;
import data.JobHistoryEntry;
import data.Person;
import org.junit.Before;
import org.junit.Test;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

public class FilterMap {

public static class Container<T, R> {
Expand Down Expand Up @@ -50,13 +62,217 @@ public LazyCollectionHelper<T> filter(Predicate<T> condition) {
}

public <R> LazyCollectionHelper<R> map(Function<T, R> function) {
// TODO
throw new UnsupportedOperationException();
List<Container<Object, Object>> newActions = new ArrayList<>(actions);
List<R> newList = new ArrayList<>();
for (T element : list) {
newList.add(function.apply(element));
}
newActions.add(new Container<>((Function<Object, Object>) function));
return new LazyCollectionHelper<R>(newList, newActions);
}

public List<T> force() {
// TODO
throw new UnsupportedOperationException();
List<T> result = new ArrayList<>();
list.forEach(result::add);
return result;
}
}

@Test
public void mapping() {
final List<Employee> employees =
Arrays.asList(
new Employee(
new Person("a", "Galt", 30),
Arrays.asList(
new JobHistoryEntry(2, "dev", "epam"),
new JobHistoryEntry(1, "dev", "google")
)),
new Employee(
new Person("b", "Doe", 40),
Arrays.asList(
new JobHistoryEntry(3, "qa", "yandex"),
new JobHistoryEntry(1, "qa", "epam"),
new JobHistoryEntry(1, "dev", "abc")
)),
new Employee(
new Person("c", "White", 50),
Collections.singletonList(
new JobHistoryEntry(5, "qa", "epam")
))
);
final List<Employee> mappedEmployees = Traversable.from(employees)
.map(e -> e.withPerson(e.getPerson().withFirstName("John"))).toList();


final List<Employee> expectedResult =
Arrays.asList(
new Employee(
new Person("John", "Galt", 30),
Arrays.asList(
new JobHistoryEntry(2, "dev", "epam"),
new JobHistoryEntry(1, "dev", "google")
)),
new Employee(
new Person("John", "Doe", 40),
Arrays.asList(
new JobHistoryEntry(3, "qa", "yandex"),
new JobHistoryEntry(1, "qa", "epam"),
new JobHistoryEntry(1, "dev", "abc")
)),
new Employee(
new Person("John", "White", 50),
Collections.singletonList(
new JobHistoryEntry(5, "qa", "epam")
))
);

assertEquals(mappedEmployees, expectedResult);
}

@Test
public void filtering() {
final List<Employee> employees =
Arrays.asList(
new Employee(
new Person("a", "Galt", 30),
Arrays.asList(
new JobHistoryEntry(2, "dev", "epam"),
new JobHistoryEntry(1, "dev", "google")
)),
new Employee(
new Person("b", "Doe", 40),
Arrays.asList(
new JobHistoryEntry(3, "qa", "yandex"),
new JobHistoryEntry(1, "qa", "epam"),
new JobHistoryEntry(1, "dev", "abc")
)),
new Employee(
new Person("c", "White", 50),
Collections.singletonList(
new JobHistoryEntry(5, "qa", "epam")
))
);

final List<Employee> filteredEmployees = Traversable.from(employees)
.filter(e -> e.getPerson().getFirstName().equals("b")).toList();

final List<Employee> expectedResult =
Arrays.asList(
new Employee(
new Person("b", "Doe", 40),
Arrays.asList(
new JobHistoryEntry(3, "qa", "yandex"),
new JobHistoryEntry(1, "qa", "epam"),
new JobHistoryEntry(1, "dev", "abc")
))
);

assertEquals(filteredEmployees, expectedResult);
}

@Test
public void flatMap() {
List<JobHistoryEntry> jobHistory2 = Arrays.asList(
new JobHistoryEntry(3, "qa", "yandex"),
new JobHistoryEntry(1, "qa", "epam"),
new JobHistoryEntry(1, "dev", "abc")
);
List<JobHistoryEntry> jobHistory1 = Arrays.asList(
new JobHistoryEntry(2, "dev", "epam"),
new JobHistoryEntry(1, "dev", "google")
);
List<JobHistoryEntry> jobHistory3 = Collections.singletonList(
new JobHistoryEntry(5, "qa", "epam")
);

final List<Employee> employees =
Arrays.asList(
new Employee(
new Person("a", "Galt", 30),
jobHistory1),
new Employee(
new Person("b", "Doe", 40),
jobHistory2),
new Employee(
new Person("c", "White", 50),
jobHistory3)
);

final List<JobHistoryEntry> employeeJobHistories = Traversable.from(employees)
.flatMap(Employee::getJobHistory).toList();

for(JobHistoryEntry e : jobHistory2) {
assertTrue(employeeJobHistories.contains(e));
}

for(JobHistoryEntry e : jobHistory1) {
assertTrue(employeeJobHistories.contains(e));
}

for(JobHistoryEntry e : jobHistory3) {
assertTrue(employeeJobHistories.contains(e));
}
}
}
interface Traversable<T> {
void forEach(Consumer<T> c);

default <R> Traversable<R> map(Function<T,R> f) {
final Traversable<T> self = this;
return new Traversable<R>() {
@Override
public void forEach(Consumer<R> c) {
self.forEach(t -> c.accept(f.apply(t)));
}
};
}

default Traversable<T> filter(Predicate<T> p) {
final Traversable<T> self = this;
return new Traversable<T>() {
@Override
public void forEach(Consumer<T> c) {
self.forEach(t -> {
if (p.test(t)) {
c.accept(t);
}
});
}
};
}

default List<T> toList() {
final List<T> result = new ArrayList<>();
forEach(result::add);
return result;
}

static <T> Traversable<T> from(List<T> list) {
return new Traversable<T>() {
@Override
public void forEach(Consumer<T> c) {
list.forEach(c);
}
};
}

default <R> Traversable<R> flatMap(Function<T,List<R>> f) {
final Traversable<T> self = this;

return new Traversable<R>() {
final List<R> result = new ArrayList<R>();
@Override
public void forEach(Consumer<R> c) {
self.forEach((T t) -> f.apply(t).forEach(c));
}
};
}
}