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src/java.base/share/classes/java/util/stream/Collectors.java
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@@ -43,20 +43,11 @@
import java.util.Optional;
import java.util.Set;
import java.util.StringJoiner;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
-import java.util.function.BiConsumer;
-import java.util.function.BiFunction;
-import java.util.function.BinaryOperator;
-import java.util.function.Consumer;
-import java.util.function.Function;
-import java.util.function.Predicate;
-import java.util.function.Supplier;
-import java.util.function.ToDoubleFunction;
-import java.util.function.ToIntFunction;
-import java.util.function.ToLongFunction;
+import java.util.function.*;
/**
* Implementations of {@link Collector} that implement various useful reduction
* operations, such as accumulating elements into collections, summarizing
* elements according to various criteria, etc.
@@ -191,28 +182,47 @@
*
* @param <T> the type of elements to be collected
* @param <R> the type of the result
*/
static class CollectorImpl<T, A, R> implements Collector<T, A, R> {
+ private final IntFunction<A> sizedSupplier;
private final Supplier<A> supplier;
private final BiConsumer<A, T> accumulator;
private final BinaryOperator<A> combiner;
private final Function<A, R> finisher;
private final Set<Characteristics> characteristics;
- CollectorImpl(Supplier<A> supplier,
+ CollectorImpl(IntFunction<A> sizedSupplier,
+ Supplier<A> supplier,
BiConsumer<A, T> accumulator,
BinaryOperator<A> combiner,
Function<A,R> finisher,
Set<Characteristics> characteristics) {
+ this.sizedSupplier = sizedSupplier;
this.supplier = supplier;
this.accumulator = accumulator;
this.combiner = combiner;
this.finisher = finisher;
this.characteristics = characteristics;
}
+ CollectorImpl(IntFunction<A> sizedSupplier,
+ Supplier<A> supplier,
+ BiConsumer<A, T> accumulator,
+ BinaryOperator<A> combiner,
+ Set<Characteristics> characteristics) {
+ this(sizedSupplier, supplier, accumulator, combiner, castingIdentity(), characteristics);
+ }
+
+ CollectorImpl(Supplier<A> supplier,
+ BiConsumer<A, T> accumulator,
+ BinaryOperator<A> combiner,
+ Function<A,R> finisher,
+ Set<Characteristics> characteristics) {
+ this(ignored -> supplier.get(), supplier, accumulator, combiner, finisher, characteristics);
+ }
+
CollectorImpl(Supplier<A> supplier,
BiConsumer<A, T> accumulator,
BinaryOperator<A> combiner,
Set<Characteristics> characteristics) {
this(supplier, accumulator, combiner, castingIdentity(), characteristics);
@@ -227,10 +237,15 @@
public Supplier<A> supplier() {
return supplier;
}
@Override
+ public IntFunction<A> sizedSupplier() {
+ return sizedSupplier;
+ }
+
+ @Override
public BinaryOperator<A> combiner() {
return combiner;
}
@Override
@@ -273,11 +288,13 @@
* @return a {@code Collector} which collects all the input elements into a
* {@code List}, in encounter order
*/
public static <T>
Collector<T, ?, List<T>> toList() {
- return new CollectorImpl<>((Supplier<List<T>>) ArrayList::new, List::add,
+ return new CollectorImpl<>((IntFunction<List<T>>) ArrayList::new,
+ (Supplier<List<T>>) ArrayList::new,
+ List::add,
(left, right) -> { left.addAll(right); return left; },
CH_ID);
}
/**
@@ -292,11 +309,13 @@
* @since 10
*/
@SuppressWarnings("unchecked")
public static <T>
Collector<T, ?, List<T>> toUnmodifiableList() {
- return new CollectorImpl<>((Supplier<List<T>>) ArrayList::new, List::add,
+ return new CollectorImpl<>((IntFunction<List<T>>) ArrayList::new,
+ (Supplier<List<T>>) ArrayList::new,
+ List::add,
(left, right) -> { left.addAll(right); return left; },
list -> (List<T>)List.of(list.toArray()),
CH_NOID);
}
@@ -364,11 +383,11 @@
* @return a {@code Collector} that concatenates the input elements into a
* {@code String}, in encounter order
*/
public static Collector<CharSequence, ?, String> joining() {
return new CollectorImpl<CharSequence, StringBuilder, String>(
- StringBuilder::new, StringBuilder::append,
+ StringBuilder::new, StringBuilder::new, StringBuilder::append,
(r1, r2) -> { r1.append(r2); return r1; },
StringBuilder::toString, CH_NOID);
}
/**
@@ -455,11 +474,11 @@
*/
public static <T, U, A, R>
Collector<T, ?, R> mapping(Function<? super T, ? extends U> mapper,
Collector<? super U, A, R> downstream) {
BiConsumer<A, ? super U> downstreamAccumulator = downstream.accumulator();
- return new CollectorImpl<>(downstream.supplier(),
+ return new CollectorImpl<>(downstream.sizedSupplier(), downstream.supplier(),
(r, t) -> downstreamAccumulator.accept(r, mapper.apply(t)),
downstream.combiner(), downstream.finisher(),
downstream.characteristics());
}
@@ -500,11 +519,11 @@
*/
public static <T, U, A, R>
Collector<T, ?, R> flatMapping(Function<? super T, ? extends Stream<? extends U>> mapper,
Collector<? super U, A, R> downstream) {
BiConsumer<A, ? super U> downstreamAccumulator = downstream.accumulator();
- return new CollectorImpl<>(downstream.supplier(),
+ return new CollectorImpl<>(downstream.sizedSupplier(), downstream.supplier(),
(r, t) -> {
try (Stream<? extends U> result = mapper.apply(t)) {
if (result != null)
result.sequential().forEach(u -> downstreamAccumulator.accept(r, u));
}
@@ -550,11 +569,11 @@
*/
public static <T, A, R>
Collector<T, ?, R> filtering(Predicate<? super T> predicate,
Collector<? super T, A, R> downstream) {
BiConsumer<A, ? super T> downstreamAccumulator = downstream.accumulator();
- return new CollectorImpl<>(downstream.supplier(),
+ return new CollectorImpl<>(downstream.sizedSupplier(), downstream.supplier(),
(r, t) -> {
if (predicate.test(t)) {
downstreamAccumulator.accept(r, t);
}
},
@@ -591,11 +610,12 @@
characteristics = EnumSet.copyOf(characteristics);
characteristics.remove(Collector.Characteristics.IDENTITY_FINISH);
characteristics = Collections.unmodifiableSet(characteristics);
}
}
- return new CollectorImpl<>(downstream.supplier(),
+ return new CollectorImpl<>(downstream.sizedSupplier(),
+ downstream.supplier(),
downstream.accumulator(),
downstream.combiner(),
downstream.finisher().andThen(finisher),
characteristics);
}
@@ -1455,10 +1475,11 @@
*/
public static <T, K, U>
Collector<T, ?, Map<K,U>> toMap(Function<? super T, ? extends K> keyMapper,
Function<? super T, ? extends U> valueMapper) {
return new CollectorImpl<>(HashMap::new,
+ HashMap::new,
uniqKeysMapAccumulator(keyMapper, valueMapper),
uniqKeysMapMerger(),
CH_ID);
}
@@ -1714,10 +1735,11 @@
*/
public static <T, K, U>
Collector<T, ?, ConcurrentMap<K,U>> toConcurrentMap(Function<? super T, ? extends K> keyMapper,
Function<? super T, ? extends U> valueMapper) {
return new CollectorImpl<>(ConcurrentHashMap::new,
+ ConcurrentHashMap::new,
uniqKeysMapAccumulator(keyMapper, valueMapper),
uniqKeysMapMerger(),
CH_CONCURRENT_ID);
}
@@ -1929,12 +1951,10 @@
BiFunction<? super R1, ? super R2, R> merger) {
Objects.requireNonNull(downstream1, "downstream1");
Objects.requireNonNull(downstream2, "downstream2");
Objects.requireNonNull(merger, "merger");
- Supplier<A1> c1Supplier = Objects.requireNonNull(downstream1.supplier(), "downstream1 supplier");
- Supplier<A2> c2Supplier = Objects.requireNonNull(downstream2.supplier(), "downstream2 supplier");
BiConsumer<A1, ? super T> c1Accumulator =
Objects.requireNonNull(downstream1.accumulator(), "downstream1 accumulator");
BiConsumer<A2, ? super T> c2Accumulator =
Objects.requireNonNull(downstream2.accumulator(), "downstream2 accumulator");
BinaryOperator<A1> c1Combiner = Objects.requireNonNull(downstream1.combiner(), "downstream1 combiner");
@@ -1954,12 +1974,24 @@
c.remove(Collector.Characteristics.IDENTITY_FINISH);
characteristics = Collections.unmodifiableSet(c);
}
class PairBox {
- A1 left = c1Supplier.get();
- A2 right = c2Supplier.get();
+ A1 left;
+ A2 right;
+
+ PairBox(int initialSize) {
+ left = Objects.requireNonNull(downstream1.sizedSupplier(), "downstream1 sizedSupplier")
+ .apply(initialSize);
+ right = Objects.requireNonNull(downstream2.sizedSupplier(), "downstream2 sizedSupplier")
+ .apply(initialSize);
+ }
+
+ PairBox() {
+ left = Objects.requireNonNull(downstream1.supplier(), "downstream1 supplier").get();
+ right = Objects.requireNonNull(downstream2.supplier(), "downstream2 supplier").get();
+ }
void add(T t) {
c1Accumulator.accept(left, t);
c2Accumulator.accept(right, t);
}
@@ -1975,11 +2007,16 @@
R2 r2 = c2Finisher.apply(right);
return merger.apply(r1, r2);
}
}
- return new CollectorImpl<>(PairBox::new, PairBox::add, PairBox::combine, PairBox::get, characteristics);
+ return new CollectorImpl<>(PairBox::new,
+ PairBox::new,
+ PairBox::add,
+ PairBox::combine,
+ PairBox::get,
+ characteristics);
}
/**
* Implementation class used by partitioningBy.
*/
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