java8新特性-引用流ReferencePipeline

ReferencePipeline实现了Stream接口，Stream接口定义了顺序和并行聚合的元素序列操作。

public interface Stream<T> extends BaseStream<T, Stream<T>> {

   
    Stream<T> filter(Predicate<? super T> predicate);

    
    <R> Stream<R> map(Function<? super T, ? extends R> mapper);

    
    IntStream mapToInt(ToIntFunction<? super T> mapper);

    
    LongStream mapToLong(ToLongFunction<? super T> mapper);

   
    DoubleStream mapToDouble(ToDoubleFunction<? super T> mapper);

    
    <R> Stream<R> flatMap(Function<? super T, ? extends Stream<? extends R>> mapper);

    
    IntStream flatMapToInt(Function<? super T, ? extends IntStream> mapper);

    
    LongStream flatMapToLong(Function<? super T, ? extends LongStream> mapper);

   
    DoubleStream flatMapToDouble(Function<? super T, ? extends DoubleStream> mapper);

   
    Stream<T> distinct();

    
    Stream<T> sorted();

   
    Stream<T> sorted(Comparator<? super T> comparator);

    
    Stream<T> peek(Consumer<? super T> action);

    
    Stream<T> limit(long maxSize);

    
     
    Stream<T> skip(long n);

    
    void forEach(Consumer<? super T> action);

    
    void forEachOrdered(Consumer<? super T> action);

    
    Object[] toArray();

    
    <A> A[] toArray(IntFunction<A[]> generator);

   
    T reduce(T identity, BinaryOperator<T> accumulator);

    
     
    Optional<T> reduce(BinaryOperator<T> accumulator);

    
    <U> U reduce(U identity,
                 BiFunction<U, ? super T, U> accumulator,
                 BinaryOperator<U> combiner);

    
    <R> R collect(Supplier<R> supplier,
                  BiConsumer<R, ? super T> accumulator,
                  BiConsumer<R, R> combiner);

   
    <R, A> R collect(Collector<? super T, A, R> collector);

    
    Optional<T> min(Comparator<? super T> comparator);

    
    Optional<T> max(Comparator<? super T> comparator);

    
    long count();

   
    boolean anyMatch(Predicate<? super T> predicate);

   
    boolean allMatch(Predicate<? super T> predicate);

   
    boolean noneMatch(Predicate<? super T> predicate);

   
    Optional<T> findFirst();

   
    Optional<T> findAny();

    
    public static<T> Builder<T> builder() {
        return new Streams.StreamBuilderImpl<>();
    }

    
    public static<T> Stream<T> empty() {
        return StreamSupport.stream(Spliterators.<T>emptySpliterator(), false);
    }

   
    public static<T> Stream<T> of(T t) {
        return StreamSupport.stream(new Streams.StreamBuilderImpl<>(t), false);
    }

    
    @SafeVarargs
    @SuppressWarnings("varargs") // Creating a stream from an array is safe
    public static<T> Stream<T> of(T... values) {
        return Arrays.stream(values);
    }

    
    public static<T> Stream<T> iterate(final T seed, final UnaryOperator<T> f) {
        Objects.requireNonNull(f);
        final Iterator<T> iterator = new Iterator<T>() {
            @SuppressWarnings("unchecked")
            T t = (T) Streams.NONE;

            @Override
            public boolean hasNext() {
                return true;
            }

            @Override
            public T next() {
                return t = (t == Streams.NONE) ? seed : f.apply(t);
            }
        };
        return StreamSupport.stream(Spliterators.spliteratorUnknownSize(
                iterator,
                Spliterator.ORDERED | Spliterator.IMMUTABLE), false);
    }

   
    public static<T> Stream<T> generate(Supplier<T> s) {
        Objects.requireNonNull(s);
        return StreamSupport.stream(
                new StreamSpliterators.InfiniteSupplyingSpliterator.OfRef<>(Long.MAX_VALUE, s), false);
    }

   
    public static <T> Stream<T> concat(Stream<? extends T> a, Stream<? extends T> b) {
        Objects.requireNonNull(a);
        Objects.requireNonNull(b);

        @SuppressWarnings("unchecked")
        Spliterator<T> split = new Streams.ConcatSpliterator.OfRef<>(
                (Spliterator<T>) a.spliterator(), (Spliterator<T>) b.spliterator());
        Stream<T> stream = StreamSupport.stream(split, a.isParallel() || b.isParallel());
        return stream.onClose(Streams.composedClose(a, b));
    }

    
    public interface Builder<T> extends Consumer<T> {

        
        @Override
        void accept(T t);

       
        default Builder<T> add(T t) {
            accept(t);
            return this;
        }

        
        Stream<T> build();

    }
}

PipelineHelper是执行流操作的流水线帮助类，捕获有关流的所有信息流水线（输出形状、中间操作、流标志、并行度、等等）：

abstract class PipelineHelper<P_OUT> {

   
    abstract StreamShape getSourceShape();

   
    abstract int getStreamAndOpFlags();

    
    abstract<P_IN> long exactOutputSizeIfKnown(Spliterator<P_IN> spliterator);

   
    abstract<P_IN, S extends Sink<P_OUT>> S wrapAndCopyInto(S sink, Spliterator<P_IN> spliterator);

    
    abstract<P_IN> void copyInto(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator);

    
    abstract <P_IN> void copyIntoWithCancel(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator);

    
    abstract<P_IN> Sink<P_IN> wrapSink(Sink<P_OUT> sink);

    
    abstract<P_IN> Spliterator<P_OUT> wrapSpliterator(Spliterator<P_IN> spliterator);

    
    abstract Node.Builder<P_OUT> makeNodeBuilder(long exactSizeIfKnown,
                                                 IntFunction<P_OUT[]> generator);

   
    abstract<P_IN> Node<P_OUT> evaluate(Spliterator<P_IN> spliterator,
                                        boolean flatten,
                                        IntFunction<P_OUT[]> generator);
}

AbstractPipeline是管道类的抽象基类，这个类是核心流接口及其原语专用化的实现。管理Sink管道的操作和评估：

abstract class AbstractPipeline<E_IN, E_OUT, S extends BaseStream<E_OUT, S>>
    extends PipelineHelper<E_OUT> implements BaseStream<E_OUT, S> {
      // 到管道链头部的反向链接（如果这是源，则为自身）
     private final AbstractPipeline sourceStage;
      // “上游”管道，如果这是源阶段，则为空。
     private final AbstractPipeline previousStage;
     // 此表示的中间操作的操作标志管道对象。
      protected final int sourceOrOpFlags;
      //管道中的下一个阶段，如果这是最后一个阶段则为空。
      private AbstractPipeline nextStage;

      //此管道对象之间的中间操作数
      private int depth;
      //源和所有操作的组合源和操作标志
      private int combinedFlags;

      //源拆分器。仅对头部管道有效。
      private Spliterator<?> sourceSpliterator;
      //源 Supplier。仅对头部管道有效。
      private Supplier<? extends Spliterator<?>> sourceSupplier;
      //如果已链接或使用此管道，则为True
      private boolean linkedOrConsumed;
      //如果是并行流则返回true
      private boolean parallel;
}