stream

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v1.2.8 Latest Latest Go to latest Published: Apr 14, 2022 License: MIT Imports: 17 Imported by: 0

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Documentation ¶

Overview ¶

A sequence of elements supporting sequential and parallel aggregate operations. The following example illustrates an aggregate operation using SEE java/util/stream/Stream.java

Index ¶

type BaseStream
type ReferencePipeline
- func New(upstreams ...interface{}) *ReferencePipeline
type Stream
- func Of(values ...interface{}) Stream

Constants ¶

This section is empty.

Variables ¶

This section is empty.

Functions ¶

This section is empty.

Types ¶

type BaseStream ¶

type BaseStream interface {
	io.Closer

	/**
	 * Returns an iterator for the elements of this stream.
	 *
	 * <p>This is a <a href="package-summary.html#StreamOps">terminal
	 * operation</a>.
	 *
	 * @return the element iterator for this stream
	 */
	Iterator() util.Iterator

	/**
	 * Returns a spliterator for the elements of this stream.
	 *
	 * <p>This is a <a href="package-summary.html#StreamOps">terminal
	 * operation</a>.
	 *
	 * <p>
	 * The returned spliterator should report the set of characteristics derived
	 * from the stream pipeline (namely the characteristics derived from the
	 * stream source spliterator and the intermediate operations).
	 * Implementations may report a sub-set of those characteristics.  For
	 * example, it may be too expensive to compute the entire set for some or
	 * all possible stream pipelines.
	 *
	 * @return the element spliterator for this stream
	 */
	Spliterator() spliterator.Spliterator

	/**
	 * Returns whether this stream, if a terminal operation were to be executed,
	 * would execute in parallel.  Calling this method after invoking an
	 * terminal stream operation method may yield unpredictable results.
	 *
	 * @return {@code true} if this stream would execute in parallel if executed
	 */
	IsParallel() bool

	/**
	 * Returns an equivalent stream that is sequential.  May return
	 * itself, either because the stream was already sequential, or because
	 * the underlying stream state was modified to be sequential.
	 *
	 * <p>This is an <a href="package-summary.html#StreamOps">intermediate
	 * operation</a>.
	 *
	 * @return a sequential stream
	 */
	Sequential() BaseStream

	/**
	 * Returns an equivalent stream that is parallel.  May return
	 * itself, either because the stream was already parallel, or because
	 * the underlying stream state was modified to be parallel.
	 *
	 * <p>This is an <a href="package-summary.html#StreamOps">intermediate
	 * operation</a>.
	 *
	 * @return a parallel stream
	 */
	Parallel() BaseStream

	/**
	 * Returns an equivalent stream that is
	 * <a href="package-summary.html#Ordering">unordered</a>.  May return
	 * itself, either because the stream was already unordered, or because
	 * the underlying stream state was modified to be unordered.
	 *
	 * <p>This is an <a href="package-summary.html#StreamOps">intermediate
	 * operation</a>.
	 *
	 * @return an unordered stream
	 */
	Unordered() BaseStream

	/**
	 * Returns an equivalent stream with an additional close handler.  Close
	 * handlers are run when the {@link #close()} method
	 * is called on the stream, and are executed in the order they were
	 * added.  All close handlers are run, even if earlier close handlers throw
	 * exceptions.  If any close handler throws an exception, the first
	 * exception thrown will be relayed to the caller of {@code close()}, with
	 * any remaining exceptions added to that exception as suppressed exceptions
	 * (unless one of the remaining exceptions is the same exception as the
	 * first exception, since an exception cannot suppress itself.)  May
	 * return itself.
	 *
	 * <p>This is an <a href="package-summary.html#StreamOps">intermediate
	 * operation</a>.
	 *
	 * @param closeHandler A task to execute when the stream is closed
	 * @return a stream with a handler that is run if the stream is closed
	 */
	OnClose(closeHandler util.Runnable) BaseStream
}

*

Base interface for streams, which are sequences of elements supporting
sequential and parallel aggregate operations. The following example
illustrates an aggregate operation using the stream types {@link Stream}
and {@link IntStream}, computing the sum of the weights of the red widgets: *
<pre>{@code
int sum = widgets.stream()
.filter(w -> w.getColor() == RED)
.mapToInt(w -> w.getWeight())
.sum();
}</pre> *
See the class documentation for {@link Stream} and the package documentation
for <a href="package-summary.html">java.util.stream</a> for additional
specification of streams, stream operations, stream pipelines, and
parallelism, which governs the behavior of all stream types. *
@param <T> the type of the stream elements
@param <S> the type of the stream implementing {@code BaseStream}
@since 1.8
@see Stream
@see IntStream
@see LongStream
@see DoubleStream
@see <a href="package-summary.html">java.util.stream</a>

type ReferencePipeline ¶

type ReferencePipeline struct {
	terminal.AbstractPipeline
	// contains filtered or unexported fields
}

func New ¶

func New(upstreams ...interface{}) *ReferencePipeline

func (*ReferencePipeline) AllMatch ¶

func (r *ReferencePipeline) AllMatch(ctx context.Context, predicate predicate.Predicater) bool

func (*ReferencePipeline) AnyMatch ¶

func (r *ReferencePipeline) AnyMatch(ctx context.Context, predicate predicate.Predicater) bool

func (*ReferencePipeline) Close ¶

func (r *ReferencePipeline) Close() error

func (*ReferencePipeline) Count ¶

func (r *ReferencePipeline) Count(ctx context.Context, comparator util.Comparator) int

func (*ReferencePipeline) Distinct ¶

func (r *ReferencePipeline) Distinct(ctx context.Context, distincter func(interface{}, interface{}) int) *ReferencePipeline

func (*ReferencePipeline) DropUntil ¶

func (r *ReferencePipeline) DropUntil(ctx context.Context, predicate predicate.Predicater) *ReferencePipeline

func (*ReferencePipeline) DropWhile ¶

func (r *ReferencePipeline) DropWhile(ctx context.Context, predicate predicate.Predicater) *ReferencePipeline

func (*ReferencePipeline) Filter ¶

func (r *ReferencePipeline) Filter(ctx context.Context, predicate predicate.Predicater) *ReferencePipeline

func (*ReferencePipeline) FindAny ¶

func (r *ReferencePipeline) FindAny(ctx context.Context, predicate predicate.Predicater) optional.Optional

func (*ReferencePipeline) FindFirst ¶

func (r *ReferencePipeline) FindFirst(ctx context.Context, predicate predicate.Predicater) optional.Optional

func (*ReferencePipeline) ForEach ¶

func (r *ReferencePipeline) ForEach(ctx context.Context, action consumer.Consumer)

func (*ReferencePipeline) ForEachOrdered ¶

func (r *ReferencePipeline) ForEachOrdered(ctx context.Context, action consumer.Consumer)

func (*ReferencePipeline) Limit ¶

func (r *ReferencePipeline) Limit(maxSize int) *ReferencePipeline

func (*ReferencePipeline) Map ¶

func (r *ReferencePipeline) Map(ctx context.Context, mapper func(interface{}) interface{}) *ReferencePipeline

func (*ReferencePipeline) Max ¶

func (r *ReferencePipeline) Max(ctx context.Context, comparator util.Comparator) optional.Optional

func (*ReferencePipeline) Min ¶

func (r *ReferencePipeline) Min(ctx context.Context, comparator util.Comparator) optional.Optional

func (*ReferencePipeline) NoneMatch ¶

func (r *ReferencePipeline) NoneMatch(ctx context.Context, predicate predicate.Predicater) bool

func (*ReferencePipeline) Peek ¶

func (r *ReferencePipeline) Peek(ctx context.Context, action consumer.Consumer) *ReferencePipeline

func (*ReferencePipeline) Reduce ¶

func (r *ReferencePipeline) Reduce(ctx context.Context,
	accumulator binary.BiFunction, combiner binary.BiFunction,
	identity ...interface{}) optional.Optional

func (*ReferencePipeline) Skip ¶

func (r *ReferencePipeline) Skip(n int) *ReferencePipeline

func (*ReferencePipeline) Sorted ¶

func (r *ReferencePipeline) Sorted(lesser func(interface{}, interface{}) int) *ReferencePipeline

func (*ReferencePipeline) TakeUntil ¶

func (r *ReferencePipeline) TakeUntil(ctx context.Context, predicate predicate.Predicater) *ReferencePipeline

func (*ReferencePipeline) TakeWhile ¶

func (r *ReferencePipeline) TakeWhile(ctx context.Context, predicate predicate.Predicater) *ReferencePipeline

func (*ReferencePipeline) ToSlice ¶

func (r *ReferencePipeline) ToSlice(generator func(interface{}) interface{}) []interface{}

type Stream ¶

type Stream interface {
	BaseStream
	Filter(ctx context.Context, predicate predicate.Predicater) Stream
	Map(ctx context.Context, f func(interface{}) interface{}) Stream
	Distinct(ctx context.Context, comparator util.Comparator) Stream
	Sorted(lesser func(interface{}, interface{}) int) Stream
	Peek(ctx context.Context, action consumer.Consumer) Stream
	Limit(maxSize int) Stream
	Skip(n int) Stream
	TakeWhile(ctx context.Context, predicate predicate.Predicater) Stream
	TakeUntil(ctx context.Context, predicate predicate.Predicater) Stream
	DropWhile(ctx context.Context, predicate predicate.Predicater) Stream
	DropUntil(ctx context.Context, predicate predicate.Predicater) Stream
	ForEach(ctx context.Context, action consumer.Consumer)
	ForEachOrdered(ctx context.Context, action consumer.Consumer)
	ToSlice() interface{}
	Reduce(ctx context.Context, accumulator binary.BiFunction, identity ...interface{}) optional.Optional
	Min(ctx context.Context, comparator util.Comparator) optional.Optional
	Max(ctx context.Context, comparator util.Comparator) optional.Optional
	Count() int
	AnyMatch(ctx context.Context, predicate predicate.Predicater) bool
	AllMatch(ctx context.Context, predicate predicate.Predicater) bool
	NoneMatch(ctx context.Context, predicate predicate.Predicater) bool
	FindFirst(ctx context.Context, predicate predicate.Predicater) optional.Optional
	FindFirstIndex(ctx context.Context, predicate predicate.Predicater) int
	FindAny(ctx context.Context, predicate predicate.Predicater) optional.Optional
	FindAnyIndex(ctx context.Context, predicate predicate.Predicater) int
	Empty() interface{}
	Of() Stream
	Concat(s2 Stream) Stream
	ConcatWithValue(v interface{}) Stream

	//grammar surger for count
	Size() int
	Length() int
}

*

A sequence of elements supporting sequential and parallel aggregate
operations. The following example illustrates an aggregate operation using
{@link Stream} and {@link IntStream}: *
<pre>{@code
int sum = widgets.stream()
.filter(w -> w.getColor() == RED)
.mapToInt(w -> w.getWeight())
.sum();
}</pre> *
In this example, {@code widgets} is a {@code Collection<Widget>}. We create
a stream of {@code Widget} objects via {@link Collection#stream Collection.stream()},
filter it to produce a stream containing only the red widgets, and then
transform it into a stream of {@code int} values representing the weight of
each red widget. Then this stream is summed to produce a total weight. *
In addition to {@code Stream}, which is a stream of object references,
there are primitive specializations for {@link IntStream}, {@link LongStream},
and {@link DoubleStream}, all of which are referred to as "streams" and
conform to the characteristics and restrictions described here. *
To perform a computation, stream
<a href="package-summary.html#StreamOps">operations</a> are composed into a
stream pipeline. A stream pipeline consists of a source (which
might be an array, a collection, a generator function, an I/O channel,
etc), zero or more intermediate operations (which transform a
stream into another stream, such as {@link Stream#filter(Predicate)}), and a
terminal operation (which produces a result or side-effect, such
as {@link Stream#count()} or {@link Stream#forEach(Consumer)}).
Streams are lazy; computation on the source data is only performed when the
terminal operation is initiated, and source elements are consumed only
as needed. *
A stream implementation is permitted significant latitude in optimizing
the computation of the result. For example, a stream implementation is free
to elide operations (or entire stages) from a stream pipeline -- and
therefore elide invocation of behavioral parameters -- if it can prove that
it would not affect the result of the computation. This means that
side-effects of behavioral parameters may not always be executed and should
not be relied upon, unless otherwise specified (such as by the terminal
operations {@code forEach} and {@code forEachOrdered}). (For a specific
example of such an optimization, see the API note documented on the
{@link #count} operation. For more detail, see the
<a href="package-summary.html#SideEffects">side-effects</a> section of the
stream package documentation.) *
Collections and streams, while bearing some superficial similarities,
have different goals. Collections are primarily concerned with the efficient
management of, and access to, their elements. By contrast, streams do not
provide a means to directly access or manipulate their elements, and are
instead concerned with declaratively describing their source and the
computational operations which will be performed in aggregate on that source.
However, if the provided stream operations do not offer the desired
functionality, the {@link #iterator()} and {@link #spliterator()} operations
can be used to perform a controlled traversal. *
A stream pipeline, like the "widgets" example above, can be viewed as
a query on the stream source. Unless the source was explicitly
designed for concurrent modification (such as a {@link ConcurrentHashMap}),
unpredictable or erroneous behavior may result from modifying the stream
source while it is being queried. *
Most stream operations accept parameters that describe user-specified
behavior, such as the lambda expression {@code w -> w.getWeight()} passed to
{@code mapToInt} in the example above. To preserve correct behavior,
these behavioral parameters:
<ul>
<li>must be <a href="package-summary.html#NonInterference">non-interfering</a>
(they do not modify the stream source); and</li>
<li>in most cases must be <a href="package-summary.html#Statelessness">stateless</a>
(their result should not depend on any state that might change during execution
of the stream pipeline).</li>
</ul> *
Such parameters are always instances of a
<a href="../function/package-summary.html">functional interface</a> such
as {@link java.util.function.Function}, and are often lambda expressions or
method references. Unless otherwise specified these parameters must be
non-null. *
A stream should be operated on (invoking an intermediate or terminal stream
operation) only once. This rules out, for example, "forked" streams, where
the same source feeds two or more pipelines, or multiple traversals of the
same stream. A stream implementation may throw {@link IllegalStateException}
if it detects that the stream is being reused. However, since some stream
operations may return their receiver rather than a new stream object, it may
not be possible to detect reuse in all cases. *
Streams have a {@link #close()} method and implement {@link AutoCloseable}.
Operating on a stream after it has been closed will throw {@link IllegalStateException}.
Most stream instances do not actually need to be closed after use, as they
are backed by collections, arrays, or generating functions, which require no
special resource management. Generally, only streams whose source is an IO channel,
such as those returned by {@link Files#lines(Path)}, will require closing. If a
stream does require closing, it must be opened as a resource within a try-with-resources
statement or similar control structure to ensure that it is closed promptly after its
operations have completed. *
Stream pipelines may execute either sequentially or in
<a href="package-summary.html#Parallelism">parallel</a>. This
execution mode is a property of the stream. Streams are created
with an initial choice of sequential or parallel execution. (For example,
{@link Collection#stream() Collection.stream()} creates a sequential stream,
and {@link Collection#parallelStream() Collection.parallelStream()} creates
a parallel one.) This choice of execution mode may be modified by the
{@link #sequential()} or {@link #parallel()} methods, and may be queried with
the {@link #isParallel()} method. *
@param <T> the type of the stream elements
@since 1.8
@see IntStream
@see LongStream
@see DoubleStream
@see <a href="package-summary.html">java.util.stream</a>

func Of ¶

func Of(values ...interface{}) Stream

*

Returns a sequential ordered stream whose elements are the specified values. *
@param <T> the type of stream elements
@param values the elements of the new stream
@return the new stream

Source Files ¶

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Directories ¶

Path	Synopsis
op
find
match
reduce
terminal
while

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