Java Characteristics类代码示例

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
/**
 * Perform a partial mutable reduction using the supplied {@link Collector}
 * on a series of adjacent elements.
 * 
 * <p>
 * This is a <a href="package-summary.html#StreamOps">quasi-intermediate</a>
 * partial reduction operation.
 * 
 * @param <R> the type of the elements in the resulting stream
 * @param <A> the intermediate accumulation type of the {@code Collector}
 * @param collapsible a non-interfering, stateless predicate to apply to the
 *        pair of adjacent elements of the input stream which returns true
 *        for elements which should be collected together.
 * @param collector a {@code Collector} which is used to combine the
 *        adjacent elements.
 * @return the new stream
 * @since 0.3.6
 */
public <R, A> StreamEx<R> collapse(BiPredicate<? super T, ? super T> collapsible,
        Collector<? super T, A, R> collector) {
    Supplier<A> supplier = collector.supplier();
    BiConsumer<A, ? super T> accumulator = collector.accumulator();
    StreamEx<A> stream = collapseInternal(collapsible, t -> {
        A acc = supplier.get();
        accumulator.accept(acc, t);
        return acc;
    }, (acc, t) -> {
        accumulator.accept(acc, t);
        return acc;
    }, collector.combiner());
    if (collector.characteristics().contains(Collector.Characteristics.IDENTITY_FINISH)) {
        @SuppressWarnings("unchecked")
        StreamEx<R> result = (StreamEx<R>) stream;
        return result;
    }
    return stream.map(collector.finisher());
}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
@SuppressWarnings("unchecked")
static <K, D, A, M extends Map<K, D>> PartialCollector<Map<K, A>, M> grouping(Supplier<M> mapFactory,
        Collector<?, A, D> downstream) {
    BinaryOperator<A> downstreamMerger = downstream.combiner();
    BiConsumer<Map<K, A>, Map<K, A>> merger = (map1, map2) -> {
        for (Map.Entry<K, A> e : map2.entrySet())
            map1.merge(e.getKey(), e.getValue(), downstreamMerger);
    };

    if (downstream.characteristics().contains(Collector.Characteristics.IDENTITY_FINISH)) {
        return (PartialCollector<Map<K, A>, M>) new PartialCollector<>((Supplier<Map<K, A>>) mapFactory,
                merger, Function.identity(), ID_CHARACTERISTICS);
    }
    Function<A, D> downstreamFinisher = downstream.finisher();
    return new PartialCollector<>((Supplier<Map<K, A>>) mapFactory, merger, map -> {
        map.replaceAll((k, v) -> ((Function<A, A>) downstreamFinisher).apply(v));
        return (M) map;
    }, NO_CHARACTERISTICS);
}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
CollectorImpl(Supplier<A> supplier, BiConsumer<A, T> accumulator, BinaryOperator<A> combiner, Function<A, R> finisher,
        Set<Characteristics> characteristics) {
    this.supplier = supplier;
    this.accumulator = accumulator;
    this.combiner = combiner;
    this.finisher = finisher;
    this.characteristics = characteristics;
}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
/**
 * Adapts a {@code Collector} to perform an additional finishing
 * transformation.  For example, one could adapt the {@link #toList()}
 * collector to always produce an immutable list with:
 * <pre>{@code
 *     List<String> people
 *         = people.stream().collect(collectingAndThen(toList(), Collections::unmodifiableList));
 * }</pre>
 *
 * @param <T> the type of the input elements
 * @param <A> intermediate accumulation type of the downstream collector
 * @param <R> result type of the downstream collector
 * @param <RR> result type of the resulting collector
 * @param downstream a collector
 * @param finisher a function to be applied to the final result of the downstream collector
 * @return a collector which performs the action of the downstream collector,
 * followed by an additional finishing step
 */
public static <T, A, R, RR> Collector<T, A, RR> collectingAndThen(final Collector<T, A, R> downstream, final Function<R, RR> finisher) {
    Objects.requireNonNull(finisher);

    final Function<A, R> downstreamFinisher = downstream.finisher();

    final Function<A, RR> thenFinisher = new Function<A, RR>() {
        @Override
        public RR apply(A t) {
            return finisher.apply(downstreamFinisher.apply(t));
        }
    };

    Set<Collector.Characteristics> characteristics = downstream.characteristics();

    if (characteristics.contains(Collector.Characteristics.IDENTITY_FINISH)) {
        if (characteristics.size() == 1)
            characteristics = Collectors.CH_NOID;
        else {
            characteristics = EnumSet.copyOf(characteristics);
            characteristics.remove(Collector.Characteristics.IDENTITY_FINISH);
            characteristics = Collections.unmodifiableSet(characteristics);
        }
    }

    return new CollectorImpl<>(downstream.supplier(), downstream.accumulator(), downstream.combiner(), thenFinisher, characteristics);
}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
/**
 * {@inheritDoc}
 * 
 * <p>
 * If special <a
 * href="package-summary.html#ShortCircuitReduction">short-circuiting
 * collector</a> is passed, this operation becomes short-circuiting as well.
 */
@Override
public <R, A> R collect(Collector<? super T, A, R> collector) {
    Predicate<A> finished = finished(collector);
    if (finished != null) {
        BiConsumer<A, ? super T> acc = collector.accumulator();
        BinaryOperator<A> combiner = collector.combiner();
        Spliterator<T> spliterator = spliterator();
        if (!isParallel()) {
            A a = collector.supplier().get();
            if (!finished.test(a)) {
                try {
                    // forEachRemaining can be much faster
                    // and take much less memory than tryAdvance for certain
                    // spliterators
                    spliterator.forEachRemaining(e -> {
                        acc.accept(a, e);
                        if (finished.test(a))
                            throw new CancelException();
                    });
                } catch (CancelException ex) {
                    // ignore
                }
            }
            return collector.finisher().apply(a);
        }
        Spliterator<A> spltr;
        if (!spliterator.hasCharacteristics(Spliterator.ORDERED)
            || collector.characteristics().contains(Characteristics.UNORDERED)) {
            spltr = new UnorderedCancellableSpliterator<>(spliterator, collector.supplier(), acc, combiner,
                    finished);
        } else {
            spltr = new OrderedCancellableSpliterator<>(spliterator, collector.supplier(), acc, combiner, finished);
        }
        return collector.finisher().apply(
            new StreamEx<>(StreamSupport.stream(spltr, true), context).findFirst().get());
    }
    return rawCollect(collector);
}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
/**
 * Adapts a {@code Collector} accepting elements of type {@code U} to one
 * accepting elements of type {@code T} by applying a flat mapping function
 * to each input element before accumulation. The flat mapping function maps
 * an input element to a {@link Stream stream} covering zero or more output
 * elements that are then accumulated downstream. Each mapped stream is
 * {@link java.util.stream.BaseStream#close() closed} after its contents
 * have been placed downstream. (If a mapped stream is {@code null} an empty
 * stream is used, instead.)
 * 
 * <p>
 * This method is similar to {@code Collectors.flatMapping} method which
 * appears in JDK 9. However when downstream collector is
 * <a href="package-summary.html#ShortCircuitReduction">short-circuiting</a>
 * , this method will also return a short-circuiting collector.
 * 
 * @param <T> the type of the input elements
 * @param <U> type of elements accepted by downstream collector
 * @param <A> intermediate accumulation type of the downstream collector
 * @param <R> result type of collector
 * @param mapper a function to be applied to the input elements, which
 *        returns a stream of results
 * @param downstream a collector which will receive the elements of the
 *        stream returned by mapper
 * @return a collector which applies the mapping function to the input
 *         elements and provides the flat mapped results to the downstream
 *         collector
 * @since 0.4.1
 */
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();
    Predicate<A> finished = finished(downstream);
    if (finished != null) {
        return new CancellableCollectorImpl<>(downstream.supplier(), (acc, t) -> {
            if (finished.test(acc))
                return;
            try (Stream<? extends U> stream = mapper.apply(t)) {
                if (stream != null) {
                    stream.spliterator().forEachRemaining(u -> {
                        downstreamAccumulator.accept(acc, u);
                        if (finished.test(acc))
                            throw new CancelException();
                    });
                }
            } catch (CancelException ex) {
                // ignore
            }
        }, downstream.combiner(), downstream.finisher(), finished, downstream.characteristics());
    }
    return Collector.of(downstream.supplier(), (acc, t) -> {
        try (Stream<? extends U> stream = mapper.apply(t)) {
            if (stream != null) {
                stream.spliterator().forEachRemaining(u -> downstreamAccumulator.accept(acc, u));
            }
        }
    }, downstream.combiner(), downstream.finisher(), downstream.characteristics().toArray(new Characteristics[0]));
}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
BaseCollector(Supplier<A> supplier, BiConsumer<A, A> merger, Function<A, R> finisher,
        Set<Characteristics> characteristics) {
    this.supplier = supplier;
    this.merger = merger;
    this.finisher = finisher;
    this.characteristics = characteristics;
}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
CancellableCollectorImpl(Supplier<A> supplier, BiConsumer<A, T> accumulator, BinaryOperator<A> combiner,
                         Function<A, R> finisher, Predicate<A> finished,
                         Set<java.util.stream.Collector.Characteristics> characteristics) {
    this.supplier = supplier;
    this.accumulator = accumulator;
    this.combiner = combiner;
    this.finisher = finisher;
    this.finished = finished;
    this.characteristics = characteristics;
}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
/**
 * Returns a {@link Collector} that accumulates the input elements into an {@link ImmutableSet}.
 *
 * @return The {@link Collector}. Will never be {@code null}.
 */
public static <T> Collector<T, ImmutableSet.Builder<T>, ImmutableSet<T>> toSet() {
	BinaryOperator<ImmutableSet.Builder<T>> combiner = (first, second) -> first.addAll(second.build());

	return Collector.of(ImmutableSet::builder, ImmutableSet.Builder::add, combiner, ImmutableSet.Builder::build,
		Characteristics.UNORDERED);
}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
public static <T, A, R, X extends Throwable> ThrowingCollector<T, A, R, X>
    of(Collector<T, A, R> collector) {
  Objects.requireNonNull(collector);
  return new ThrowingCollector<T, A, R, X>() {
    @Override
    public ThrowingSupplier<A, X> supplier() {
      return collector.supplier()::get;
    }

    @Override
    public ThrowingBiConsumer<A, T, X> accumulator() {
      return collector.accumulator()::accept;
    }

    @Override
    public ThrowingBinaryOperator<A, X> combiner() {
      return collector.combiner()::apply;
    }

    @Override
    public ThrowingFunction<A, R, X> finisher() {
      return collector.finisher()::apply;
    }

    @Override
    public Set<Characteristics> characteristics() {
      return collector.characteristics();
    }
  };
}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
public static <T> Collector<T, ?, Multiset<T>> toMultiSet( final Supplier<Multiset<T>> supplier ){		

		return Collector.of(
				supplier,
				( set, t ) -> set.add( t ),
				( l, r ) -> { l.addAll( r ); return l; },
				l -> l,
				Characteristics.IDENTITY_FINISH );
	}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
public static <T extends Comparable<?>> Collector<T, ImmutableSortedSet.Builder<T>, ImmutableSortedSet<T>> toImmutableSortedSetReversed() {		

		return Collector.of(
				ImmutableSortedSet::<T> reverseOrder,
				ImmutableSortedSet.Builder<T>::add,
				(l, r) -> l.addAll(r.build()), 
				ImmutableSortedSet.Builder<T>::build,
				Characteristics.UNORDERED);
	}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
public static <T> Collector<T, ?, ImmutableSortedSet<T>> toImmutableSortedSet( final Supplier<Builder<T>> supplier ){

		return Collector.of(
				supplier,
				ImmutableSortedSet.Builder<T>::add,
				(l, r) -> l.addAll(r.build()), 
				ImmutableSortedSet.Builder<T>::build,
				Characteristics.UNORDERED);
	}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
public static <T, K, V> Collector<T,?,BiMap<K,V>> toBiMap(
		final Supplier<BiMap<K,V>> supplier,
		final Function<T,K> keyFunction,
		final Function<T,V> valueFunction ){

	return Collector.of( 
			supplier,
			(map, value) -> map.put( keyFunction.apply( value ), valueFunction.apply( value )),
			(l, r) -> { l.putAll( r ); return l;},
			map -> map,
			Characteristics.IDENTITY_FINISH	);		
}
 

import java.util.stream.Collector.Characteristics; //导入依赖的package包/类
public static <T, R, C, V> Collector<T,?,Table<R,C,V>> toTable( 
		final Function<T,R> rowFunction,
		final Function<T,C> columnFunction,
		final Function<T,V> valueFunction ){

	return Collector.of( 
			HashBasedTable::<R,C,V> create,
			(table, value ) -> table.put( rowFunction.apply( value ), columnFunction.apply( value ), valueFunction.apply( value )),
			(l, r) -> { l.putAll( r ); return l; },
			table -> table,
			Characteristics.IDENTITY_FINISH);		
}