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67 changes: 52 additions & 15 deletions src/test/java/part2/exercise/CollectorsExercise1.java
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Original file line number Diff line number Diff line change
Expand Up @@ -6,25 +6,19 @@
import org.junit.Test;

import java.util.*;
import java.util.concurrent.ThreadLocalRandom;
import java.util.function.BiConsumer;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

import static java.util.stream.Collectors.toList;
import static java.util.stream.Collectors.*;
import static org.junit.Assert.assertEquals;

public class CollectorsExercise1 {

@Test
public void getTheCoolestOne() {
final Map<String, Person> coolestByPosition = getCoolestByPosition(getEmployees());
final Map<String, Person> coolestByPositionFirst = getCoolestByPositionFirst(getEmployees());
final Map<String, Person> coolestByPositionSecond = getCoolestByPositionSecond(getEmployees());

coolestByPosition.forEach((position, person) -> System.out.println(position + " -> " + person));
assertEquals(coolestByPositionFirst, coolestByPositionSecond);
}

private static class PersonPositionDuration {
Expand Down Expand Up @@ -52,17 +46,40 @@ public int getDuration() {
}

// With the longest duration on single job
private Map<String, Person> getCoolestByPosition(List<Employee> employees) {
private Map<String, Person> getCoolestByPositionFirst(List<Employee> employees) {
// First option
// Collectors.maxBy
// Collectors.collectingAndThen
// Collectors.groupingBy
// TODO
return employees.stream()
.flatMap(e -> e.getJobHistory().stream()
.map(j -> new PersonPositionDuration(e.getPerson(), j.getPosition(), j.getDuration())))
.collect(
groupingBy(
PersonPositionDuration::getPosition,
collectingAndThen(
maxBy(Comparator.comparingInt(PersonPositionDuration::getDuration)),
o -> o.orElseThrow(IllegalStateException::new).getPerson()
)
)
);
}

private Map<String, Person> getCoolestByPositionSecond(List<Employee> employees) {
// Second option
// Collectors.toMap
// iterate twice: stream...collect(...).stream()...
// TODO
throw new UnsupportedOperationException();
return employees.stream()
.flatMap(e -> e.getJobHistory().stream()
.map(j -> new PersonPositionDuration(e.getPerson(), j.getPosition(), j.getDuration())))
.collect(toMap(
PersonPositionDuration::getPosition,
o -> new PersonPositionDuration(o.getPerson(), null, o.getDuration()),
(p1, p2) -> p1.getDuration() > p2.getDuration() ? p1 : p2
)).entrySet().stream()
.collect(toMap(Map.Entry::getKey, o -> o.getValue().getPerson()));
}

@Test
Expand All @@ -76,7 +93,27 @@ public void getTheCoolestOne2() {
// { John Doe, [{dev, google, 4}, {dev, epam, 4}] } предпочтительнее, чем { A B, [{dev, google, 6}, {QA, epam, 100}]}
private Map<String, Person> getCoolestByPosition2(List<Employee> employees) {
// TODO
throw new UnsupportedOperationException();
return employees.stream()
.flatMap(e -> e.getJobHistory().stream()
.map(j -> new PersonPositionDuration(e.getPerson(), j.getPosition(), j.getDuration())))
.collect(
groupingBy(
PersonPositionDuration::getPosition,
collectingAndThen(
groupingBy(
PersonPositionDuration::getPerson,
summingInt(PersonPositionDuration::getDuration)
),
m -> {
Map.Entry<Person, Integer> maxEntry = null;
for (Map.Entry<Person, Integer> entry : m.entrySet())
if (maxEntry == null || entry.getValue().compareTo(maxEntry.getValue()) > 0)
maxEntry = entry;
return maxEntry.getKey();
}
)
)
);
}

private List<Employee> getEmployees() {
Expand Down Expand Up @@ -151,7 +188,7 @@ private List<Employee> getEmployees() {
new Employee(
new Person("Bob", "White", 31),
Collections.singletonList(
new JobHistoryEntry(6, "QA", "epam")
new JobHistoryEntry(10, "QA", "epam")
))
);
}
Expand Down
128 changes: 100 additions & 28 deletions src/test/java/part2/exercise/CollectorsExercise2.java
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Original file line number Diff line number Diff line change
@@ -1,8 +1,5 @@
package part2.exercise;

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

import java.util.*;
Expand All @@ -12,11 +9,11 @@
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

import static java.util.stream.Collectors.toList;
import static java.util.stream.Collectors.*;
import static org.junit.Assert.assertEquals;

public class CollectorsExercise2 {

Expand All @@ -28,7 +25,7 @@ private static String generateString() {
return IntStream.range(0, length)
.mapToObj(letters::charAt)
.map(Object::toString)
.collect(Collectors.joining());
.collect(joining());
}

private static String[] generateStringArray(int length) {
Expand Down Expand Up @@ -99,20 +96,26 @@ public Value getValue() {
}
}

public static List<Pair> generatePairs(int idCount, int length) {
public static Set<Pair> generatePairs(int idCount, int length) {
final String[] ids = generateStringArray(idCount);

return Stream.generate(() -> new Pair(new Key(pickString(ids)), new Value(pickString(ids))))
.limit(length)
.collect(toList());
.collect(toSet());
}

private static class SubResult {
private final Map<Key, List<Value>> subResult;
private final Map<String, List<Key>> knownKeys;
private final Map<String, Key> knownKeys;
private final Map<String, List<Value>> valuesWithoutKeys;

public SubResult(Map<Key, List<Value>> subResult, Map<String, List<Key>> knownKeys, Map<String, List<Value>> valuesWithoutKeys) {
public SubResult(Map<Key, List<Value>> subResult) {
this.subResult = subResult;
this.knownKeys = null;
this.valuesWithoutKeys = null;
}

public SubResult(Map<Key, List<Value>> subResult, Map<String, Key> knownKeys, Map<String, List<Value>> valuesWithoutKeys) {
this.subResult = subResult;
this.knownKeys = knownKeys;
this.valuesWithoutKeys = valuesWithoutKeys;
Expand All @@ -126,7 +129,7 @@ public Map<String, List<Value>> getValuesWithoutKeys() {
return valuesWithoutKeys;
}

public Map<String, List<Key>> getKnownKeys() {
public Map<String, Key> getKnownKeys() {
return knownKeys;
}
}
Expand All @@ -135,22 +138,34 @@ private static class MapPair {
private final Map<String, Key> keyById;
private final Map<String, List<Value>> valueById;

public MapPair() {
MapPair() {
this(new HashMap<>(), new HashMap<>());
}

public MapPair(Map<String, Key> keyById, Map<String, List<Value>> valueById) {
MapPair(Map<String, Key> keyById, Map<String, List<Value>> valueById) {
this.keyById = keyById;
this.valueById = valueById;
}

public Map<String, Key> getKeyById() {
Map<String, Key> getKeyById() {
return keyById;
}

public Map<String, List<Value>> getValueById() {
Map<String, List<Value>> getValueById() {
return valueById;
}

void put(Pair p) {
keyById.put(p.getKey().getId(), p.getKey());
final ArrayList<Value> value = new ArrayList<>();
value.add(p.getValue());
valueById.merge(p.getValue().getKeyId(),
value,
(l1, l2) -> {
l1.addAll(l2);
return l1;
});
}
}

private static <K, V, M extends Map<K, V>>
Expand All @@ -165,35 +180,59 @@ BinaryOperator<M> mapMerger(BinaryOperator<V> mergeFunction) {

@Test
public void collectKeyValueMap() {
final List<Pair> pairs = generatePairs(10, 100);
final Set<Pair> pairs = generatePairs(10, 100);

// В два прохода
// final Map<String, Key> keyMap1 = pairs.stream()...

// final Map<String, List<Value>> valuesMap1 = pairs.stream()...
final Map<String, Key> keyMap1 = pairs.stream()
.collect(toMap(o -> o.getKey().getId(), Pair::getKey, (k1, k2) -> k1));

final Map<String, List<Value>> valuesMap1 = pairs.stream()
.collect(toMap(
o -> o.getValue().getKeyId(),
t -> {
final ArrayList<Value> values = new ArrayList<>();
values.add(t.getValue());
return values;
},
(l1, l2) -> {
l1.addAll(l2);
return l1;
}
));

// В каждом Map.Entry id ключа должно совпадать с keyId для каждого значения в списке
// final Map<Key, List<Value>> keyValuesMap1 = valueMap1.entrySet().stream()...
final Map<Key, List<Value>> keyValuesMap1 = valuesMap1.entrySet().stream()
.collect(toMap(o -> keyMap1.get(o.getKey()), Map.Entry::getValue));

// В 1 проход в 2 Map с использованием MapPair и mapMerger
final MapPair res2 = pairs.stream()
.collect(new Collector<Pair, MapPair, MapPair>() {
@Override
public Supplier<MapPair> supplier() {
// TODO
throw new UnsupportedOperationException();
return MapPair::new;
}

@Override
public BiConsumer<MapPair, Pair> accumulator() {
// TODO add key and value to maps
throw new UnsupportedOperationException();
return MapPair::put;
}

@Override
public BinaryOperator<MapPair> combiner() {
// TODO use mapMerger
throw new UnsupportedOperationException();
return (mapPair, mapPair2) -> {
BinaryOperator<Map<String, Key>> keyMerger = mapMerger((v1, v2) -> v1);
keyMerger.apply(mapPair.getKeyById(), mapPair2.getKeyById());
BinaryOperator<Map<String, List<Value>>> valueMerger =
mapMerger((v1, v2) -> {
v1.addAll(v2);
return v1;
});
valueMerger.apply(mapPair.getValueById(), mapPair2.getValueById());
return mapPair;
};
}

@Override
Expand All @@ -212,7 +251,8 @@ public Set<Characteristics> characteristics() {
final Map<String, Key> keyMap2 = res2.getKeyById();
final Map<String, List<Value>> valuesMap2 = res2.getValueById();

// final Map<Key, List<Value>> keyValuesMap2 = valueMap2.entrySet().stream()...
final Map<Key, List<Value>> keyValuesMap2 = valuesMap1.entrySet().stream()
.collect(toMap(o -> keyMap1.get(o.getKey()), Map.Entry::getValue));

// Получение результата сразу:

Expand All @@ -221,25 +261,54 @@ public Set<Characteristics> characteristics() {
@Override
public Supplier<SubResult> supplier() {
// TODO
throw new UnsupportedOperationException();
return () -> new SubResult(new HashMap<>(), new HashMap<>(), new HashMap<>());
}

@Override
public BiConsumer<SubResult, Pair> accumulator() {
// TODO add key to map, then check value.keyId and add it to one of maps
throw new UnsupportedOperationException();
return (subResult, pair) -> {
subResult.getKnownKeys().put(
pair.getKey().getId(),
pair.getKey());
final Map<String, List<Value>> values =
subResult.getValuesWithoutKeys();
if (values.containsKey(pair.getValue().getKeyId()))
values.get(pair.getValue().getKeyId())
.add(pair.getValue());
else {
List<Value> value = new ArrayList<>();
value.add(pair.getValue());
values.put(
pair.getValue().getKeyId(),
value);
}
};
}

@Override
public BinaryOperator<SubResult> combiner() {
// TODO use mapMerger, then check all valuesWithoutKeys
throw new UnsupportedOperationException();
return (subResult1, subResult2) -> {
BinaryOperator<Map<String, Key>> keyMerger = mapMerger((v1, v2) -> v1);
keyMerger.apply(subResult1.getKnownKeys(), subResult2.getKnownKeys());
BinaryOperator<Map<String, List<Value>>> valueMerger =
mapMerger((v1, v2) -> {
v1.addAll(v2);
return v1;
});
valueMerger.apply(subResult1.getValuesWithoutKeys(), subResult2.getValuesWithoutKeys());
return subResult1;
};
}

@Override
public Function<SubResult, SubResult> finisher() {
// TODO use mapMerger, then check all valuesWithoutKeys
throw new UnsupportedOperationException();
final Function<SubResult, Map<Key, List<Value>>> getResult =
subResult -> subResult.getValuesWithoutKeys().entrySet().stream()
.collect(toMap(o -> subResult.getKnownKeys().get(o.getKey()), Map.Entry::getValue));
return subResult -> new SubResult(getResult.apply(subResult));
}

@Override
Expand All @@ -251,6 +320,9 @@ public Set<Characteristics> characteristics() {

final Map<Key, List<Value>> keyValuesMap3 = res3.getSubResult();

assertEquals(keyValuesMap1, keyValuesMap2);
assertEquals(keyValuesMap1, keyValuesMap3);

// compare results
}

Expand Down
3 changes: 2 additions & 1 deletion src/test/java/part3/exercise/CollectorCombination.java
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@

import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.Function;
import java.util.stream.Collector;

Expand Down Expand Up @@ -46,7 +47,7 @@ public void collectKeyValueMap() {
// .collect(new Collector<Pair, MapPair, MapPair>() {

// Перепишите решение в слещующем виде:
final List<CollectorsExercise2.Pair> pairs = CollectorsExercise2.generatePairs(10, 100);
final Set<CollectorsExercise2.Pair> pairs = CollectorsExercise2.generatePairs(10, 100);

final Pair<Map<String, Key>, Map<String, List<Value>>> res2 = pairs.stream()
.collect(
Expand Down