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Golubev Nikita - Part3 #187

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98384b7
[WIP] part3
Jul 9, 2017
9cbf3ba
part3
Jul 11, 2017
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219 changes: 214 additions & 5 deletions src/test/java/lambda/part3/exercise/Mapping.java
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,6 @@
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
Expand All @@ -32,8 +31,9 @@ public List<T> getList() {
// [T] -> (T -> R) -> [R]
// [T1, T2, T3] -> (T -> R) -> [R1, R2, R3]
public <R> MapHelper<R> map(Function<T, R> f) {
// TODO
throw new UnsupportedOperationException();
List<R> rs = new ArrayList<>();
list.forEach(t -> rs.add(f.apply(t)));
return new MapHelper<>(rs);
}

// [T] -> (T -> [R]) -> [R]
Expand All @@ -43,13 +43,25 @@ public <R> MapHelper<R> map(Function<T, R> f) {
public <R> MapHelper<R> flatMap(Function<T, List<R>> f) {
final List<R> result = new ArrayList<R>();
list.forEach((T t) ->
f.apply(t).forEach(result::add)
result.addAll(f.apply(t))
);

return new MapHelper<R>(result);
}
}

private List<JobHistoryEntry> addOneYear(List<JobHistoryEntry> entries){
MapHelper<JobHistoryEntry> res = new MapHelper<>(entries);
return res.map(e -> e.withDuration(e.getDuration() + 1)).getList();
}

private List<JobHistoryEntry> renamePosition(List<JobHistoryEntry> entries, String from, String to){
return new MapHelper<>(entries)
.map(jobHistoryEntry -> jobHistoryEntry.getPosition().equals(from) ?
jobHistoryEntry.withPosition(to) :
jobHistoryEntry).getList();
}

@Test
public void mapping() {
final List<Employee> employees =
Expand All @@ -76,12 +88,15 @@ public void mapping() {

final List<Employee> mappedEmployees =
new MapHelper<>(employees)
.map(employee -> employee.withPerson(employee.getPerson().withFirstName("John")))
.map(employee -> employee.withJobHistory(addOneYear(employee.getJobHistory())))
.map(employee -> employee.withJobHistory(renamePosition(employee.getJobHistory(), "qa", "QA")))
.getList();
/*
.map(TODO) // change name to John .map(e -> e.withPerson(e.getPerson().withFirstName("John")))
.map(TODO) // add 1 year to experience duration .map(e -> e.withJobHistory(addOneYear(e.getJobHistory())))
.map(TODO) // replace qa with QA
* */
.getList();

final List<Employee> expectedResult =
Arrays.asList(
Expand Down Expand Up @@ -224,4 +239,198 @@ public void lazy_mapping() {

assertEquals(mappedEmployees, expectedResult);
}


interface Traversable<T> {
void forEach(Consumer<T> c);

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

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

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

default List<T> force() {
final List<T> res = new ArrayList<>();
this.forEach(res::add);
return res;
}
}

@Test
public void traversalMapTests() {

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")))
.force();

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 traversalFilterTests() {
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().getAge() == 40).force();

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 traversalFlatMapTests() {
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<JobHistoryEntry> flatMappedEmployees =
Traversable.from(employees)
.filter(e -> e.getPerson().getAge() == 40)
.flatMap(e -> Traversable.from(e.getJobHistory())).force();

final List<JobHistoryEntry> expectedResult =
Arrays.asList(
new JobHistoryEntry(3, "qa", "yandex"),
new JobHistoryEntry(1, "qa", "epam"),
new JobHistoryEntry(1, "dev", "abc")

);

assertEquals(flatMappedEmployees, expectedResult);
}
}