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Nazarov_Anton/part-3 #176

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348386c
part-3
Podvodku Jul 6, 2017
e04846a
ReachIter, Traversable
Podvodku Jul 6, 2017
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2 changes: 2 additions & 0 deletions src/test/java/lambda/part3/exercise/FilterMap.java
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@

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

Expand Down Expand Up @@ -30,6 +31,7 @@ public Function<T, R> getFunction() {
}
}


public static class LazyCollectionHelper<T> {
private final List<Container<Object, Object>> actions;
private final List<T> list;
Expand Down
176 changes: 142 additions & 34 deletions src/test/java/lambda/part3/exercise/Mapping.java
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Original file line number Diff line number Diff line change
@@ -1,15 +1,12 @@
package lambda.part3.exercise;

import com.sun.org.apache.regexp.internal.RE;
import data.Employee;
import data.JobHistoryEntry;
import data.Person;
import org.junit.Test;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.function.BiConsumer;
import java.util.*;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
Expand All @@ -18,6 +15,15 @@

public class Mapping {

private List<JobHistoryEntry> addOneYear(List<JobHistoryEntry> jobs) {
return new MapHelper<>(jobs).map(j -> j.withDuration(j.getDuration() + 1)).getList();
}

private List<JobHistoryEntry> upperCaseQa(List<JobHistoryEntry> jobs) {
return new MapHelper<>(jobs).map(j -> j.getPosition().equals("qa") ? j.withPosition(j.getPosition().toUpperCase()) : j).getList();
//TOASK how should i format this code? Should i use statement lambda for better reading?
}

private static class MapHelper<T> {
private final List<T> list;

Expand All @@ -32,21 +38,24 @@ 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();
final List<R> result = new ArrayList<>();
for (T t : list) {
result.add(f.apply(t));
}
return new MapHelper<>(result);
}

// [T] -> (T -> [R]) -> [R]

// map: [T, T, T], T -> [R] => [[], [R1, R2], [R3, R4, R5]]
// flatMap: [T, T, T], T -> [R] => [R1, R2, R3, R4, R5]
public <R> MapHelper<R> flatMap(Function<T, List<R>> f) {
final List<R> result = new ArrayList<R>();
final List<R> result = new ArrayList<>();
list.forEach((T t) ->
f.apply(t).forEach(result::add)
result.addAll(f.apply(t))
);

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

Expand Down Expand Up @@ -76,12 +85,9 @@ public void mapping() {

final List<Employee> mappedEmployees =
new MapHelper<>(employees)
/*
.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();
.map(e -> e.withPerson(e.getPerson().withFirstName("John")))
.map(e -> e.withJobHistory(addOneYear(e.getJobHistory())))
.map(e -> e.withJobHistory(upperCaseQa(e.getJobHistory()))).getList();

final List<Employee> expectedResult =
Arrays.asList(
Expand Down Expand Up @@ -110,44 +116,59 @@ public void mapping() {


private static class LazyMapHelper<T, R> {
private final Function<T, R> function;
private final List<T> list;


public LazyMapHelper(List<T> list, Function<T, R> function) {
this.list = list;
this.function = function;
}

public static <T> LazyMapHelper<T, T> from(List<T> list) {
return new LazyMapHelper<>(list, Function.identity());
}

public List<R> force() {
// TODO
throw new UnsupportedOperationException();
final List<R> result = new ArrayList<>();
for (T t : list) {
result.add(function.apply(t));
}
return result;
}

public <R2> LazyMapHelper<T, R2> map(Function<R, R2> f) {
// TODO
throw new UnsupportedOperationException();
return new LazyMapHelper<>(list, function.andThen(f));
}

}

private static class LazyFlatMapHelper<T, R> {
private List<T> list;
private Function<T, List<R>> function;

public LazyFlatMapHelper(List<T> list, Function<T, List<R>> function) {
this.list = list;
this.function = function;
}

public static <T> LazyFlatMapHelper<T, T> from(List<T> list) {
throw new UnsupportedOperationException();
return new LazyFlatMapHelper<>(list, Arrays::asList);
}

public List<R> force() {
// TODO
throw new UnsupportedOperationException();
final List<R> result = new ArrayList<>();
for (T t : list) {
result.addAll(function.apply(t));
}
return result;
}

// TODO filter
// (T -> boolean) -> (T -> [T])
// filter: [T1, T2] -> (T -> boolean) -> [T2]
// flatMap": [T1, T2] -> (T -> [T]) -> [T2]
public LazyFlatMapHelper<T, R> filter(final Predicate<T> predicate) {
return new LazyFlatMapHelper<>(list, e -> predicate.test(e) ? function.apply(e) : Collections.emptyList());
}

public <R2> LazyFlatMapHelper<T, R2> map(Function<R, R2> f) {
final Function<R, List<R2>> listFunction = rR2TorListR2(f);
Expand All @@ -156,16 +177,104 @@ public <R2> LazyFlatMapHelper<T, R2> map(Function<R, R2> f) {

// (R -> R2) -> (R -> [R2])
private <R2> Function<R, List<R2>> rR2TorListR2(Function<R, R2> f) {
throw new UnsupportedOperationException();
return e -> Collections.singletonList(f.apply(e));
}

// TODO *
public <R2> LazyFlatMapHelper<T, R2> flatMap(Function<R, List<R2>> f) {
throw new UnsupportedOperationException();
return new LazyFlatMapHelper<>(list, t -> new MapHelper<>(function.apply(t)).flatMap(f).getList());
}
}

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

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 Traversable<T> filter(Predicate<T> p) {
return c -> this.forEach(v -> {
if (p.test(v)) {
c.accept(v);
}
});
}

default <R> Traversable<R> flatMap(Function<T, Traversable<R>> f) {
return c -> this.forEach(t -> f.apply(t).forEach(c));
}

default <R> Traversable<R> map(Function<T, R> f) {
return c -> this.forEach(t -> c.accept(f.apply(t)));
}
}

@Test
public void traversable() {
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("a")).toList();

final List<Employee> expectedResult =
Arrays.asList(
new Employee(
new Person("a", "Galt", 30),
Arrays.asList(
new JobHistoryEntry(2, "dev", "epam"),
new JobHistoryEntry(1, "dev", "google")
))
);

assertEquals(filteredEmployees, expectedResult);

final List<JobHistoryEntry> flattedJobs =
Traversable.from(employees)
.filter(e -> e.getPerson().getLastName().length() < 5)
.flatMap(e -> Traversable.from(e.getJobHistory())).toList();

final List<JobHistoryEntry> jobs = Arrays.asList(
new JobHistoryEntry(2, "dev", "epam"),
new JobHistoryEntry(1, "dev", "google"),
new JobHistoryEntry(3, "qa", "yandex"),
new JobHistoryEntry(1, "qa", "epam"),
new JobHistoryEntry(1, "dev", "abc")
);

assertEquals(flattedJobs, jobs);
}

@Test
public void lazy_mapping() {
Expand Down Expand Up @@ -193,12 +302,9 @@ public void lazy_mapping() {

final List<Employee> mappedEmployees =
LazyMapHelper.from(employees)
/*
.map(TODO) // change name to John
.map(TODO) // add 1 year to experience duration
.map(TODO) // replace qa with QA
* */
.force();
.map(e -> e.withPerson(e.getPerson().withFirstName("John")))
.map(e -> e.withJobHistory(addOneYear(e.getJobHistory())))
.map(e -> e.withJobHistory(upperCaseQa(e.getJobHistory()))).force();

final List<Employee> expectedResult =
Arrays.asList(
Expand All @@ -225,3 +331,5 @@ public void lazy_mapping() {
assertEquals(mappedEmployees, expectedResult);
}
}


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