StreamストリームとLambda式(3)静的ファクトリクラスCollectors
/**
* @author
*/
@SpringBootTest
@RunWith(SpringRunner.class)
public class CollectorsDetail {
private List names;
private List students;
private List> snames;
@Before
public void init() {
names = Arrays.asList("Kirito", "Asuna", "Sinon", "Yuuki", "Alice");
snames = Arrays.asList(Collections.singletonList("Kirito"), Collections.singletonList("Asuna"),
Collections.singletonList("Sinon"), Collections.singletonList("Yuuki"),
Collections.singletonList("Alice"));
students = new Students().init();
}
@Test
public void testCollectorsDetail() {
一、静的工場類Collectors実現方式
// 、 Collectors
// Collectors CollectorImpl
// 1、 CollectorImpl
// 2、 reducing() ---> reducing() CollectorImpl
// Collectors.toList() Collectors.toCollection()
// Collectors.joining() StringBuilder.append 二、静的工場類Collectors常用コレクター
// 、 Collectors
/*
（ ）unmodifiable List ArrayList encounter order
@since 10
@SuppressWarnings("unchecked")
public static
Collector> toUnmodifiableList() {
return new CollectorImpl<>((Supplier>) ArrayList::new, List::add,
(left, right) -> { left.addAll(right); return left; },
list -> (List)List.of(list.toArray()),
CH_NOID);
}*/
/*
（ ）unmodifiable Set HashSet
@since 10
@SuppressWarnings("unchecked")
public static
Collector> toUnmodifiableSet() {
return new CollectorImpl<>((Supplier>) HashSet::new, Set::add,
(left, right) -> {
if (left.size() < right.size()) {
right.addAll(left); return right;
} else {
left.addAll(right); return left;
}
},
set -> (Set)Set.of(set.toArray()),
CH_UNORDERED_NOID);
}
*/
/*
flatMapping mapper downstream
@since 9
public static
Collector flatMapping(Function super T, ? extends Stream extends U>> mapper,
Collector super U, A, R> downstream) {
BiConsumerdownstreamAccumulator = downstream.accumulator();
return new CollectorImpl<>(downstream.supplier(),
(r, t) -> {
try (Stream extends U> result = mapper.apply(t)) {
if (result != null)
result.sequential().forEach(u -> downstreamAccumulator.accept(r, u));
}
},
downstream.combiner(), downstream.finisher(),
downstream.characteristics());
}*/
/*
Predicateの に するフィルタリングfiltering downstreamを して を
@since 9
public static
Collector filtering(Predicate super T> predicate,
Collector super T, A, R> downstream) {
BiConsumerdownstreamAccumulator = downstream.accumulator();
return new CollectorImpl<>(downstream.supplier(),
(r, t) -> {
if (predicate.test(t)) {
downstreamAccumulator.accept(r, t);
}
},
downstream.combiner(), downstream.finisher(),
downstream.characteristics());
}*/
/*
Mapを してkey-->keyMapper-->Key value-->valueMapper-->Value
マッピングした をアセンブリするentrySet->Map(unmodifiable Map)
@since 10
@SuppressWarnings({"rawtypes", "unchecked"})
public static
Collector> toUnmodifiableMap(Function super T, ? extends K> keyMapper,
Function super T, ? extends U> valueMapper) {
Objects.requireNonNull(keyMapper, "keyMapper");
Objects.requireNonNull(valueMapper, "valueMapper");
return collectingAndThen(
toMap(keyMapper, valueMapper),
map -> (Map)Map.ofEntries(map.entrySet().toArray(new Map.Entry[0])));
}*/
/*
Mapを してkey-->keyMapper-->Key value-->valueMapper-->Value
mergeFunction じkeyマッピング のValueマージ
マッピングした をアセンブリするentrySet->Map(unmodifiable Map)
@since 10
@SuppressWarnings({"rawtypes", "unchecked"})
public static
Collector> toUnmodifiableMap(Function super T, ? extends K> keyMapper,
Function super T, ? extends U> valueMapper,
BinaryOperator mergeFunction) {
Objects.requireNonNull(keyMapper, "keyMapper");
Objects.requireNonNull(valueMapper, "valueMapper");
Objects.requireNonNull(mergeFunction, "mergeFunction");
return collectingAndThen(
toMap(keyMapper, valueMapper, mergeFunction, HashMap::new),
map -> (Map)Map.ofEntries(map.entrySet().toArray(new Map.Entry[0])));
}*/
// Collectors
System.out.println("-----------------------------------------
");
// ArrayList
List unmodifiableList = names.stream().collect(Collectors.toUnmodifiableList());
System.out.println(unmodifiableList);
System.out.println("---------------------------------------
");
// HashSet
Set unmodifiableSet = names.stream().collect(Collectors.toUnmodifiableSet());
System.out.println(unmodifiableSet);
System.out.println("---------------------------------------
");
// ArrayList
List strings = snames.stream()
.collect(Collectors.flatMapping(list -> list.stream().map(String::toUpperCase), Collectors.toList()));
System.out.println(strings);
System.out.println("---------------------------------------
");
// ArrayList
List filteringPredicate = names.stream().collect(Collectors.filtering("Kirito"::equals,
Collectors.toList()));
System.out.println(filteringPredicate);
System.out.println("---------------------------------------
");
// key-->keyMapper value-->valueMapper Map
Map> listMap = students.stream()
.collect(Collectors.toUnmodifiableMap(Student::getId, student -> {
List stus = new ArrayList<>();
stus.add(student);
return stus;
}));
System.out.println(listMap);
System.out.println("---------------------------------------
");
// key-->keyMapper-->Key value-->valueMapper-->Value
// Key Value
Map lengthName = names.stream()
.collect(Collectors.toUnmodifiableMap(String::length,
String::toString, (str1, str2) -> str1 + "\t" + str2));
System.out.println(lengthName);
System.out.println("---------------------------------------
"); 三、groupingByグループ
// 、groupingBy
// groupingBy
// T key --> classifier--> value--> Map
/*
Returns a {@code Collector} implementing a "group by" operation on
input elements of type {@code T}, grouping elements according to a
classification function, and returning the results in a {@code Map}.
The classification function maps elements to some key type {@code K}.
The collector produces a {@code Map>} whose keys are the
values resulting from applying the classification function to the input
elements, and whose corresponding values are {@code List}s containing the
input elements which map to the associated key under the classification
function.
There are no guarantees on the type, mutability, serializability, or
thread-safety of the {@code Map} or {@code List} objects returned.*/
/*
key T classifier
List
public static Collector>>
groupingBy(Function super T, ? extends K> classifier) {
return groupingBy(classifier, toList());
}*/
/*
key T classifier
downstream
public static
Collector> groupingBy(Function super T, ? extends K> classifier,
Collector super T, A, D> downstream) {
return groupingBy(classifier, HashMap::new, downstream);
}*/
/*
key T classifier
mapFactory downstream CollectorImpl
downstream
public static >
Collector groupingBy(Function super T, ? extends K> classifier,
Supplier mapFactory,
Collector super T, A, D> downstream) {
SupplierdownstreamSupplier = downstream.supplier();
BiConsumerdownstreamAccumulator = downstream.accumulator();
BiConsumer, T> accumulator = (m, t) -> {
K key = Objects.requireNonNull(classifier.apply(t), "element cannot be mapped to a null key");
A container = m.computeIfAbsent(key, k -> downstreamSupplier.get());
downstreamAccumulator.accept(container, t);
};
BinaryOperator> merger = Collectors.>mapMerger(downstream.combiner());
@SuppressWarnings("unchecked")
Supplier> mangledFactory = (Supplier>) mapFactory;
// なしでCollectorImplを
if (downstream.characteristics().contains(Collector.Characteristics.IDENTITY_FINISH)) {
return new CollectorImpl<>(mangledFactory, accumulator, merger, CH_ID);
}
else {
// によるCollectorImplの
@SuppressWarnings("unchecked")
FunctiondownstreamFinisher = (Function) downstream.finisher();
Function, M> finisher = intermediate -> {
intermediate.replaceAll((k, v) -> downstreamFinisher.apply(v));
@SuppressWarnings("unchecked")
M castResult = (M) intermediate;
return castResult;
};
return new CollectorImpl<>(mangledFactory, accumulator, merger, finisher, CH_NOID);
}
}*/
//
System.out.println("-----------------------------------------
");
// select * from students group by sex ;
Map> sexStudent =
students.stream().collect(Collectors.groupingBy(Student::getSex));
System.out.println(sexStudent);
System.out.println("-----------------------------------------
");
// select sex, count(*) from students group by sex ;
Map sexCount =
students.stream().collect(Collectors.groupingBy(Student::getSex, Collectors.counting()));
System.out.println(sexCount);
System.out.println("-----------------------------------------
");
// select sex,avg(salary) from students group by sex ;
Map avgSexSalary = students.stream().collect
(Collectors.groupingBy(Student::getSex, Collectors.averagingDouble(Student::getSalary)));
System.out.println(avgSexSalary);
System.out.println("-----------------------------------------
");
// sex addr
Map>> NestedGroupBy = students.stream()
.collect(Collectors.groupingBy(Student::getSex, Collectors.groupingBy(Student::getAddr)));
System.out.println(NestedGroupBy);
System.out.println("-----------------------------------------
");
// downstream HashSet
Map> sexHashSet = students.stream()
.collect(Collectors.groupingBy(Student::getSex, Collectors.toCollection(HashSet::new)));
System.out.println(sexHashSet);
System.out.println("-----------------------------------------
");
// downstream HashSet CollectorImpl
Map> sexCustomCollectorImpl = students.stream()
.collect(Collectors.groupingBy(Student::getSex, Hashtable::new, Collectors.toCollection(HashSet::new)));
System.out.println(sexCustomCollectorImpl);
System.out.println("-----------------------------------------
"); 四、groupingByConcurrentグループ
// 、groupingByConcurrent
// groupingByConcurrent
// ：
// Collector.Characteristics.UNORDERED
// Collector.Characteristics.CONCURRENT
// This is a {@link Collector.Characteristics#CONCURRENT concurrent} and
// {@link Collector.Characteristics#UNORDERED unordered} Collector.
/*
key T classifier
List
public static
Collector>>
groupingByConcurrent(Function super T, ? extends K> classifier) {
return groupingByConcurrent(classifier, ::new, toList());
}*/
/*
key T classifier
downstream
public static
Collector> groupingByConcurrent(Function super T, ? extends K> classifier,
Collector super T, A, D> downstream) {
return groupingByConcurrent(classifier, ConcurrentHashMap::new, downstream);
}*/
/*
key T classifier
mapFactory downstream CollectorImpl
downstream
public static >
Collector groupingByConcurrent(Function super T, ? extends K> classifier,
Supplier mapFactory,
Collector super T, A, D> downstream) {
SupplierdownstreamSupplier = downstream.supplier();
BiConsumerdownstreamAccumulator = downstream.accumulator();
BinaryOperator> merger = Collectors.>mapMerger(downstream.combiner());
@SuppressWarnings("unchecked")
Supplier> mangledFactory = (Supplier>) mapFactory;
BiConsumer, T> accumulator;
if (downstream.characteristics().contains(Collector.Characteristics.CONCURRENT)) {
accumulator = (m, t) -> {
K key = Objects.requireNonNull(classifier.apply(t), "element cannot be mapped to a null key");
A resultContainer = m.computeIfAbsent(key, k -> downstreamSupplier.get());
downstreamAccumulator.accept(resultContainer, t);
};
}
else {
accumulator = (m, t) -> {
K key = Objects.requireNonNull(classifier.apply(t), "element cannot be mapped to a null key");
A resultContainer = m.computeIfAbsent(key, k -> downstreamSupplier.get());
// のアクション--> じ コンテナを に --> じ 、 のアクションは1つのみ-->スレッド
synchronized (resultContainer) {
downstreamAccumulator.accept(resultContainer, t);
}
};
}
if (downstream.characteristics().contains(Collector.Characteristics.IDENTITY_FINISH)) {
return new CollectorImpl<>(mangledFactory, accumulator, merger, CH_CONCURRENT_ID);
}
else {
@SuppressWarnings("unchecked")
FunctiondownstreamFinisher = (Function) downstream.finisher();
Function, M> finisher = intermediate -> {
intermediate.replaceAll((k, v) -> downstreamFinisher.apply(v));
@SuppressWarnings("unchecked")
M castResult = (M) intermediate;
return castResult;
};
return new CollectorImpl<>(mangledFactory, accumulator, merger, finisher, CH_CONCURRENT_NOID);
}
}*/ //
System.out.println("-----------------------------------------
");
// ArrayList
ConcurrentMap> sexStudentConcurrent = students.stream()
.collect(Collectors.groupingByConcurrent(Student::getSex));
System.out.println(sexStudentConcurrent);
System.out.println("-----------------------------------------
");
// downstream HashSet
ConcurrentMap> sexHashSetConcurrent = students.stream()
.collect(Collectors.groupingByConcurrent(Student::getSex, Collectors.toCollection(HashSet::new)));
System.out.println(sexHashSetConcurrent);
System.out.println("-----------------------------------------
");
// downstream HashSet CollectorImpl
ConcurrentReferenceHashMap> sexCustomCollectorImplConcurrent =
students.stream().collect(Collectors.groupingByConcurrent(Student::getSex,
ConcurrentReferenceHashMap::new, Collectors.toCollection(HashSet::new)));
System.out.println(sexCustomCollectorImplConcurrent);
System.out.println("-----------------------------------------
"); 五、partitioningByパーティション
// 、partitioningBy
// partitioningBy
/*
ArrayList
public static
Collector>> partitioningBy(Predicate super T> predicate) {
return partitioningBy(predicate, toList());
}*/
/*
downstream
public static
Collector> partitioningBy(Predicate super T> predicate,
Collector super T, A, D> downstream) {
BiConsumerdownstreamAccumulator = downstream.accumulator();
BiConsumer, T> accumulator = (result, t) ->
downstreamAccumulator.accept(predicate.test(t) ? result.forTrue : result.forFalse, t);
BinaryOperatorop = downstream.combiner();
BinaryOperator> merger = (left, right) ->
new Partition<>(op.apply(left.forTrue, right.forTrue),
op.apply(left.forFalse, right.forFalse));
Supplier> supplier = () ->
new Partition<>(downstream.supplier().get(),
downstream.supplier().get());
if (downstream.characteristics().contains(Collector.Characteristics.IDENTITY_FINISH)) {
return new CollectorImpl<>(supplier, accumulator, merger, CH_ID);
}
else {
Function, Map> finisher = par ->
new Partition<>(downstream.finisher().apply(par.forTrue),
downstream.finisher().apply(par.forFalse));
return new CollectorImpl<>(supplier, accumulator, merger, finisher, CH_NOID);
}
}*/ //
System.out.println("-----------------------------------------
");
// select * from students partition by (addr == Sword Art Online) ;
Map> addrPartition = students.stream().collect
(Collectors.partitioningBy(student -> student.getAddr().equals("Sword Art Online")));
System.out.println(addrPartition);
System.out.println("-----------------------------------------
");
// sex addr
Map>> NestedPartiton = students.stream()
.collect(Collectors.partitioningBy(student -> student.getSex().equals("Male"),
Collectors.partitioningBy(student -> student.getAddr().equals("Sword Art Online"))));
System.out.println(NestedPartiton);
System.out.println("-----------------------------------------
");
// downstream
Map> addrCustomPartition = students.stream().collect(Collectors.partitioningBy
(student -> student.getAddr().equals("Sword Art Online"), Collectors.toCollection(HashSet::new)));
System.out.println(addrCustomPartition);
System.out.println("-----------------------------------------
");
}
} 六、テスト結果
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.2.RELEASE)
2019-02-20 16:58:15.870 INFO 13392 --- [ main] c.j.d.java8.Stream.CollectorsDetail : Starting CollectorsDetail on DESKTOP-87RMBG4 with PID 13392 (started by 46250 in E:\IdeaProjects\design)
2019-02-20 16:58:15.871 INFO 13392 --- [ main] c.j.d.java8.Stream.CollectorsDetail : No active profile set, falling back to default profiles: default
2019-02-20 16:58:16.383 INFO 13392 --- [ main] c.j.d.java8.Stream.CollectorsDetail : Started CollectorsDetail in 0.708 seconds (JVM running for 1.421)
-----------------------------------------
[Kirito, Asuna, Sinon, Yuuki, Alice]
---------------------------------------
[Yuuki, Asuna, Kirito, Sinon, Alice]
---------------------------------------
[KIRITO, ASUNA, SINON, YUUKI, ALICE]
---------------------------------------
[Kirito]
---------------------------------------
{5=[Student(id=5, name=Alice, sex=Female, age=14, addr=Alicization, salary=9.99999999E8)], 4=[Student(id=4, name=Yuuki, sex=Female, age=15, addr=Alfheim Online, salary=9.99999999E8)], 3=[Student(id=3, name=Sinon, sex=Female, age=16, addr=Gun Gale Online, salary=9.99999999E8)], 2=[Student(id=2, name=Asuna, sex=Female, age=17, addr=Sword Art Online, salary=9.99999999E8)], 1=[Student(id=1, name=Kirito, sex=Male, age=18, addr=Sword Art Online, salary=9.99999999E8)]}
---------------------------------------
{6=Kirito, 5=Asuna Sinon Yuuki Alice}
---------------------------------------
-----------------------------------------
{Female=[Student(id=2, name=Asuna, sex=Female, age=17, addr=Sword Art Online, salary=9.99999999E8), Student(id=3, name=Sinon, sex=Female, age=16, addr=Gun Gale Online, salary=9.99999999E8), Student(id=4, name=Yuuki, sex=Female, age=15, addr=Alfheim Online, salary=9.99999999E8), Student(id=5, name=Alice, sex=Female, age=14, addr=Alicization, salary=9.99999999E8)], Male=[Student(id=1, name=Kirito, sex=Male, age=18, addr=Sword Art Online, salary=9.99999999E8)]}
-----------------------------------------
{Female=4, Male=1}
-----------------------------------------
{Female=9.99999999E8, Male=9.99999999E8}
-----------------------------------------
{Female={Alicization=[Student(id=5, name=Alice, sex=Female, age=14, addr=Alicization, salary=9.99999999E8)], Sword Art Online=[Student(id=2, name=Asuna, sex=Female, age=17, addr=Sword Art Online, salary=9.99999999E8)], Gun Gale Online=[Student(id=3, name=Sinon, sex=Female, age=16, addr=Gun Gale Online, salary=9.99999999E8)], Alfheim Online=[Student(id=4, name=Yuuki, sex=Female, age=15, addr=Alfheim Online, salary=9.99999999E8)]}, Male={Sword Art Online=[Student(id=1, name=Kirito, sex=Male, age=18, addr=Sword Art Online, salary=9.99999999E8)]}}
-----------------------------------------
{Female=[Student(id=4, name=Yuuki, sex=Female, age=15, addr=Alfheim Online, salary=9.99999999E8), Student(id=3, name=Sinon, sex=Female, age=16, addr=Gun Gale Online, salary=9.99999999E8), Student(id=5, name=Alice, sex=Female, age=14, addr=Alicization, salary=9.99999999E8), Student(id=2, name=Asuna, sex=Female, age=17, addr=Sword Art Online, salary=9.99999999E8)], Male=[Student(id=1, name=Kirito, sex=Male, age=18, addr=Sword Art Online, salary=9.99999999E8)]}
-----------------------------------------
{Female=[Student(id=4, name=Yuuki, sex=Female, age=15, addr=Alfheim Online, salary=9.99999999E8), Student(id=3, name=Sinon, sex=Female, age=16, addr=Gun Gale Online, salary=9.99999999E8), Student(id=5, name=Alice, sex=Female, age=14, addr=Alicization, salary=9.99999999E8), Student(id=2, name=Asuna, sex=Female, age=17, addr=Sword Art Online, salary=9.99999999E8)], Male=[Student(id=1, name=Kirito, sex=Male, age=18, addr=Sword Art Online, salary=9.99999999E8)]}
-----------------------------------------
-----------------------------------------
{Male=[Student(id=1, name=Kirito, sex=Male, age=18, addr=Sword Art Online, salary=9.99999999E8)], Female=[Student(id=2, name=Asuna, sex=Female, age=17, addr=Sword Art Online, salary=9.99999999E8), Student(id=3, name=Sinon, sex=Female, age=16, addr=Gun Gale Online, salary=9.99999999E8), Student(id=4, name=Yuuki, sex=Female, age=15, addr=Alfheim Online, salary=9.99999999E8), Student(id=5, name=Alice, sex=Female, age=14, addr=Alicization, salary=9.99999999E8)]}
-----------------------------------------
{Male=[Student(id=1, name=Kirito, sex=Male, age=18, addr=Sword Art Online, salary=9.99999999E8)], Female=[Student(id=4, name=Yuuki, sex=Female, age=15, addr=Alfheim Online, salary=9.99999999E8), Student(id=3, name=Sinon, sex=Female, age=16, addr=Gun Gale Online, salary=9.99999999E8), Student(id=5, name=Alice, sex=Female, age=14, addr=Alicization, salary=9.99999999E8), Student(id=2, name=Asuna, sex=Female, age=17, addr=Sword Art Online, salary=9.99999999E8)]}
-----------------------------------------
{Female=[Student(id=4, name=Yuuki, sex=Female, age=15, addr=Alfheim Online, salary=9.99999999E8), Student(id=3, name=Sinon, sex=Female, age=16, addr=Gun Gale Online, salary=9.99999999E8), Student(id=5, name=Alice, sex=Female, age=14, addr=Alicization, salary=9.99999999E8), Student(id=2, name=Asuna, sex=Female, age=17, addr=Sword Art Online, salary=9.99999999E8)], Male=[Student(id=1, name=Kirito, sex=Male, age=18, addr=Sword Art Online, salary=9.99999999E8)]}
-----------------------------------------
-----------------------------------------
{false=[Student(id=3, name=Sinon, sex=Female, age=16, addr=Gun Gale Online, salary=9.99999999E8), Student(id=4, name=Yuuki, sex=Female, age=15, addr=Alfheim Online, salary=9.99999999E8), Student(id=5, name=Alice, sex=Female, age=14, addr=Alicization, salary=9.99999999E8)], true=[Student(id=1, name=Kirito, sex=Male, age=18, addr=Sword Art Online, salary=9.99999999E8), Student(id=2, name=Asuna, sex=Female, age=17, addr=Sword Art Online, salary=9.99999999E8)]}
-----------------------------------------
{false={false=[Student(id=3, name=Sinon, sex=Female, age=16, addr=Gun Gale Online, salary=9.99999999E8), Student(id=4, name=Yuuki, sex=Female, age=15, addr=Alfheim Online, salary=9.99999999E8), Student(id=5, name=Alice, sex=Female, age=14, addr=Alicization, salary=9.99999999E8)], true=[Student(id=2, name=Asuna, sex=Female, age=17, addr=Sword Art Online, salary=9.99999999E8)]}, true={false=[], true=[Student(id=1, name=Kirito, sex=Male, age=18, addr=Sword Art Online, salary=9.99999999E8)]}}
-----------------------------------------
{false=[Student(id=4, name=Yuuki, sex=Female, age=15, addr=Alfheim Online, salary=9.99999999E8), Student(id=3, name=Sinon, sex=Female, age=16, addr=Gun Gale Online, salary=9.99999999E8), Student(id=5, name=Alice, sex=Female, age=14, addr=Alicization, salary=9.99999999E8)], true=[Student(id=2, name=Asuna, sex=Female, age=17, addr=Sword Art Online, salary=9.99999999E8), Student(id=1, name=Kirito, sex=Male, age=18, addr=Sword Art Online, salary=9.99999999E8)]}
-----------------------------------------