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homework part2 #74

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62f3d96
Added getCoolestByPosition
Jul 11, 2017
d23eada
CollectorsExercise1 is done
Jul 13, 2017
43eaecc
CollectorsExercise2 is done
Jul 13, 2017
ac8cdbc
CollectorsExercise2 is done
Jul 13, 2017
f838408
CollectorsExercise2 is done
Jul 17, 2017
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60 changes: 55 additions & 5 deletions src/test/java/part2/exercise/CollectorsExercise1.java
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@
import java.util.stream.IntStream;
import java.util.stream.Stream;

import static java.util.stream.Collectors.toList;
import static java.util.stream.Collectors.*;

public class CollectorsExercise1 {

Expand Down Expand Up @@ -61,8 +61,10 @@ private Map<String, Person> getCoolestByPosition(List<Employee> employees) {
// Second option
// Collectors.toMap
// iterate twice: stream...collect(...).stream()...
// TODO
throw new UnsupportedOperationException();
return getPersonPositionDurationStream(employees)
.collect(groupingBy(PersonPositionDuration::getPosition,
collectingAndThen(maxBy(Comparator.comparing(PersonPositionDuration::getDuration)),
p -> p.get().getPerson())));
}

@Test
Expand All @@ -72,11 +74,59 @@ public void getTheCoolestOne2() {
coolestByPosition.forEach((position, person) -> System.out.println(position + " -> " + person));
}

private Stream<PersonPositionDuration> getPersonPositionDurationStream(List<Employee> employees) {
return employees.stream().flatMap(e -> e.getJobHistory().stream()
.map(j -> new PersonPositionDuration(e.getPerson(), j.getPosition(), j.getDuration())));
}

// With the longest sum duration on this position
// { 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 getPersonPositionDurationStream(employees).collect(
new Collector<PersonPositionDuration, Map<String, PersonPositionDuration>, Map<String, Person>>() {
@Override
public Supplier<Map<String, PersonPositionDuration>> supplier() {
return HashMap::new;
}

@Override
public BiConsumer<Map<String, PersonPositionDuration>, PersonPositionDuration> accumulator() {
return (map, ppd) -> {
map.putIfAbsent(ppd.getPosition(), ppd);
PersonPositionDuration currentPpd = map.get(ppd.getPosition());
if (ppd.getDuration() > currentPpd.getDuration()) {
map.put(ppd.getPosition(), ppd);
}
};
}

@Override
public BinaryOperator<Map<String, PersonPositionDuration>> combiner() {
return (m1, m2) -> {
m2.forEach((k, v) -> m1.merge(k, v, (v1, v2) -> v1.getDuration() > v2.getDuration() ? v1 : v2));
return m1;
};
}

@Override
public Function<Map<String, PersonPositionDuration>, Map<String, Person>> finisher() {
return map -> map.entrySet()
.stream()
.collect(
Collectors.toMap(
Map.Entry::getKey,
item -> item.getValue().getPerson()
)
);
}

@Override
public Set<Characteristics> characteristics() {
return Collections.unmodifiableSet(EnumSet.of(Characteristics.UNORDERED));
}
}
);
}

private List<Employee> getEmployees() {
Expand Down
91 changes: 49 additions & 42 deletions src/test/java/part2/exercise/CollectorsExercise2.java
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,9 @@
import java.util.stream.Stream;

import static java.util.stream.Collectors.toList;
import static java.util.stream.Collectors.toMap;
import static org.hamcrest.core.IsEqual.equalTo;
import static org.junit.Assert.assertThat;

public class CollectorsExercise2 {

Expand Down Expand Up @@ -176,24 +179,61 @@ public void collectKeyValueMap() {
// final Map<Key, List<Value>> keyValuesMap1 = valueMap1.entrySet().stream()...

// В 1 проход в 2 Map с использованием MapPair и mapMerger

Map<String, Key> keyMap1 = pairs.stream()
.collect(
toMap(
p -> p.getKey().getId(),
Pair::getKey,
(v1, v2) -> v1
)
);

Map<String, List<Value>> valuesMap1 = pairs.stream()
.collect(
Collectors.groupingBy(
p -> p.getValue().getKeyId(),
Collectors.mapping(Pair::getValue, toList())
)
);

Map<Key, List<Value>> keyValuesMap1 = valuesMap1.entrySet().stream()
.collect(
toMap(
p -> keyMap1.get(p.getKey()),
Map.Entry::getValue
)
);
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 (mp, p) -> {
mp.getKeyById().computeIfAbsent(p.getKey().getId(), q -> p.getKey());
mp.getValueById().computeIfAbsent(p.getValue().getKeyId(), q -> new ArrayList<>())
.add(p.getValue());

};
}

@Override
public BinaryOperator<MapPair> combiner() {
// TODO use mapMerger
throw new UnsupportedOperationException();
return (mp1,mp2) -> {
BinaryOperator<Map<String, Key>> binaryOperator = mapMerger((v1,v2) -> v1);
Map<String,Key> map = binaryOperator.apply(mp1.getKeyById(), mp2.getKeyById());
BinaryOperator<Map<String, List<Value>>> mapBinaryOperator = mapMerger((v1,v2) -> {
v1.addAll(v2);
return v1;
});
Map<String, List<Value>> listMap = mapBinaryOperator.apply(mp1.getValueById(),
mp2.getValueById());
return new MapPair(map, listMap);
};
}

@Override
Expand All @@ -214,44 +254,11 @@ public Set<Characteristics> characteristics() {

// final Map<Key, List<Value>> keyValuesMap2 = valueMap2.entrySet().stream()...

// Получение результата сразу:

final SubResult res3 = pairs.stream()
.collect(new Collector<Pair, SubResult, SubResult>() {
@Override
public Supplier<SubResult> supplier() {
// TODO
throw new UnsupportedOperationException();
}

@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();
}

@Override
public BinaryOperator<SubResult> combiner() {
// TODO use mapMerger, then check all valuesWithoutKeys
throw new UnsupportedOperationException();
}

@Override
public Function<SubResult, SubResult> finisher() {
// TODO use mapMerger, then check all valuesWithoutKeys
throw new UnsupportedOperationException();
}

@Override
public Set<Characteristics> characteristics() {
return Collections.unmodifiableSet(EnumSet.of(
Characteristics.UNORDERED));
}
});

final Map<Key, List<Value>> keyValuesMap3 = res3.getSubResult();
final Map<Key, List<Value>> keyValuesMap2 = valuesMap2.entrySet().stream().collect(toMap(e -> keyMap2.get(e.getKey()), Map.Entry::getValue));

// compare results
assertThat(keyMap1, equalTo(keyMap2));
assertThat(keyValuesMap1.keySet(), equalTo(keyValuesMap2.keySet()));
}

}