jdk.util.stream.Stream
A sequence of elements supporting sequential and parallel aggregate operations. The following example illustrates an aggregate operation using Stream and IntStream:
int sum = widgets.stream()
.filter(w -> w.getColor() == RED)
.mapToInt(w -> w.getWeight())
.sum();
In this example, widgets is a Collection<Widget>. We create a stream of Widget objects via Collection.stream(), filter it to produce a stream containing only the red widgets, and then transform it into a stream of int values representing the weight of each red widget. Then this stream is summed to produce a total weight.
In addition to Stream, which is a stream of object references, there are primitive specializations for IntStream, LongStream, and DoubleStream, all of which are referred to as "streams" and conform to the characteristics and restrictions described here.
To perform a computation, stream operations 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 filter(Predicate)), and a terminal operation (which produces a result or side-effect, such as count() or 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.
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 BaseStream.iterator() and BaseStream.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 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 w -> w.getWeight() passed to mapToInt in the example above. To preserve correct behavior, these behavioral parameters:
must be non-interfering (they do not modify the stream source); and in most cases must be stateless (their result should not depend on any state that might change during execution of the stream pipeline).
Such parameters are always instances of a functional interface such as 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 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 BaseStream.close() method and implement AutoCloseable, but nearly all stream instances do not actually need to be closed after use. Generally, only streams whose source is an IO channel (such as those returned by Files.lines(Path, Charset)) will require closing. Most streams are backed by collections, arrays, or generating functions, which require no special resource management. (If a stream does require closing, it can be declared as a resource in a try-with-resources statement.)
Stream pipelines may execute either sequentially or in parallel. This execution mode is a property of the stream. Streams are created with an initial choice of sequential or parallel execution. (For example, Collection.stream() creates a sequential stream, and Collection.parallelStream() creates a parallel one.) This choice of execution mode may be modified by the BaseStream.sequential() or BaseStream.parallel() methods, and may be queried with the BaseStream.isParallel() method.
A sequence of elements supporting sequential and parallel aggregate
operations. The following example illustrates an aggregate operation using
Stream and IntStream:
int sum = widgets.stream()
.filter(w -> w.getColor() == RED)
.mapToInt(w -> w.getWeight())
.sum();
In this example, widgets is a Collection<Widget>. We create
a stream of Widget objects via Collection.stream(),
filter it to produce a stream containing only the red widgets, and then
transform it into a stream of int values representing the weight of
each red widget. Then this stream is summed to produce a total weight.
In addition to Stream, which is a stream of object references,
there are primitive specializations for IntStream, LongStream,
and DoubleStream, all of which are referred to as "streams" and
conform to the characteristics and restrictions described here.
To perform a computation, stream
operations 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 filter(Predicate)), and a
terminal operation (which produces a result or side-effect, such
as count() or 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.
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 BaseStream.iterator() and BaseStream.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 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 w -> w.getWeight() passed to
mapToInt in the example above. To preserve correct behavior,
these behavioral parameters:
must be non-interfering
(they do not modify the stream source); and
in most cases must be stateless
(their result should not depend on any state that might change during execution
of the stream pipeline).
Such parameters are always instances of a
functional interface such
as 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 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 BaseStream.close() method and implement AutoCloseable,
but nearly all stream instances do not actually need to be closed after use.
Generally, only streams whose source is an IO channel (such as those returned
by Files.lines(Path, Charset)) will require closing. Most streams
are backed by collections, arrays, or generating functions, which require no
special resource management. (If a stream does require closing, it can be
declared as a resource in a try-with-resources statement.)
Stream pipelines may execute either sequentially or in
parallel. This
execution mode is a property of the stream. Streams are created
with an initial choice of sequential or parallel execution. (For example,
Collection.stream() creates a sequential stream,
and Collection.parallelStream() creates
a parallel one.) This choice of execution mode may be modified by the
BaseStream.sequential() or BaseStream.parallel() methods, and may be queried with
the BaseStream.isParallel() method.*builderclj
(*builder)Returns a builder for a Stream.
returns: a stream builder - <T> java.util.stream.Stream$Builder<T>
Returns a builder for a Stream. returns: a stream builder - `<T> java.util.stream.Stream$Builder<T>`
*concatclj
(*concat a b)Creates a lazily concatenated stream whose elements are all the elements of the first stream followed by all the elements of the second stream. The resulting stream is ordered if both of the input streams are ordered, and parallel if either of the input streams is parallel. When the resulting stream is closed, the close handlers for both input streams are invoked.
a - the first stream - java.util.stream.Stream
b - the second stream - java.util.stream.Stream
returns: the concatenation of the two input streams - <T> java.util.stream.Stream<T>
Creates a lazily concatenated stream whose elements are all the elements of the first stream followed by all the elements of the second stream. The resulting stream is ordered if both of the input streams are ordered, and parallel if either of the input streams is parallel. When the resulting stream is closed, the close handlers for both input streams are invoked. a - the first stream - `java.util.stream.Stream` b - the second stream - `java.util.stream.Stream` returns: the concatenation of the two input streams - `<T> java.util.stream.Stream<T>`
*emptyclj
(*empty)Returns an empty sequential Stream.
returns: an empty sequential stream - <T> java.util.stream.Stream<T>
Returns an empty sequential Stream. returns: an empty sequential stream - `<T> java.util.stream.Stream<T>`
*generateclj
(*generate s)Returns an infinite sequential unordered stream where each element is generated by the provided Supplier. This is suitable for generating constant streams, streams of random elements, etc.
s - the Supplier of generated elements - java.util.function.Supplier
returns: a new infinite sequential unordered Stream - <T> java.util.stream.Stream<T>
Returns an infinite sequential unordered stream where each element is generated by the provided Supplier. This is suitable for generating constant streams, streams of random elements, etc. s - the Supplier of generated elements - `java.util.function.Supplier` returns: a new infinite sequential unordered Stream - `<T> java.util.stream.Stream<T>`
*iterateclj
(*iterate seed f)Returns an infinite sequential ordered Stream produced by iterative application of a function f to an initial element seed, producing a Stream consisting of seed, f(seed), f(f(seed)), etc.
The first element (position 0) in the Stream will be the provided seed. For n > 0, the element at position n, will be the result of applying the function f to the element at position n - 1.
seed - the initial element - T
f - a function to be applied to to the previous element to produce a new element - java.util.function.UnaryOperator
returns: a new sequential Stream - <T> java.util.stream.Stream<T>
Returns an infinite sequential ordered Stream produced by iterative application of a function f to an initial element seed, producing a Stream consisting of seed, f(seed), f(f(seed)), etc. The first element (position 0) in the Stream will be the provided seed. For n > 0, the element at position n, will be the result of applying the function f to the element at position n - 1. seed - the initial element - `T` f - a function to be applied to to the previous element to produce a new element - `java.util.function.UnaryOperator` returns: a new sequential Stream - `<T> java.util.stream.Stream<T>`
*ofclj
(*of t)Returns a sequential Stream containing a single element.
t - the single element - T
returns: a singleton sequential stream - <T> java.util.stream.Stream<T>
Returns a sequential Stream containing a single element. t - the single element - `T` returns: a singleton sequential stream - `<T> java.util.stream.Stream<T>`
all-matchclj
(all-match this predicate)Returns whether all elements of this stream match the provided predicate. May not evaluate the predicate on all elements if not necessary for determining the result. If the stream is empty then true is returned and the predicate is not evaluated.
This is a short-circuiting terminal operation.
predicate - a non-interfering, stateless predicate to apply to elements of this stream - java.util.function.Predicate
returns: true if either all elements of the stream match the
provided predicate or the stream is empty, otherwise false - boolean
Returns whether all elements of this stream match the provided predicate. May not evaluate the predicate on all elements if not necessary for determining the result. If the stream is empty then true is returned and the predicate is not evaluated. This is a short-circuiting terminal operation. predicate - a non-interfering, stateless predicate to apply to elements of this stream - `java.util.function.Predicate` returns: true if either all elements of the stream match the provided predicate or the stream is empty, otherwise false - `boolean`
any-matchclj
(any-match this predicate)Returns whether any elements of this stream match the provided predicate. May not evaluate the predicate on all elements if not necessary for determining the result. If the stream is empty then false is returned and the predicate is not evaluated.
This is a short-circuiting terminal operation.
predicate - a non-interfering, stateless predicate to apply to elements of this stream - java.util.function.Predicate
returns: true if any elements of the stream match the provided
predicate, otherwise false - boolean
Returns whether any elements of this stream match the provided predicate. May not evaluate the predicate on all elements if not necessary for determining the result. If the stream is empty then false is returned and the predicate is not evaluated. This is a short-circuiting terminal operation. predicate - a non-interfering, stateless predicate to apply to elements of this stream - `java.util.function.Predicate` returns: true if any elements of the stream match the provided predicate, otherwise false - `boolean`
collectclj
(collect this collector)(collect this supplier accumulator combiner)Performs a mutable reduction operation on the elements of this stream. A mutable reduction is one in which the reduced value is a mutable result container, such as an ArrayList, and elements are incorporated by updating the state of the result rather than by replacing the result. This produces a result equivalent to:
R result = supplier.get();
for (T element : this stream)
accumulator.accept(result, element);
return result;
Like reduce(Object, BinaryOperator), collect operations can be parallelized without requiring additional synchronization.
This is a terminal operation.
supplier - a function that creates a new result container. For a parallel execution, this function may be called multiple times and must return a fresh value each time. - java.util.function.Supplier
accumulator - an associative, non-interfering, stateless function for incorporating an additional element into a result - java.util.function.BiConsumer
combiner - an associative, non-interfering, stateless function for combining two values, which must be compatible with the accumulator function - java.util.function.BiConsumer
returns: the result of the reduction - <R> R
Performs a mutable
reduction operation on the elements of this stream. A mutable
reduction is one in which the reduced value is a mutable result container,
such as an ArrayList, and elements are incorporated by updating
the state of the result rather than by replacing the result. This
produces a result equivalent to:
R result = supplier.get();
for (T element : this stream)
accumulator.accept(result, element);
return result;
Like reduce(Object, BinaryOperator), collect operations
can be parallelized without requiring additional synchronization.
This is a terminal
operation.
supplier - a function that creates a new result container. For a parallel execution, this function may be called multiple times and must return a fresh value each time. - `java.util.function.Supplier`
accumulator - an associative, non-interfering, stateless function for incorporating an additional element into a result - `java.util.function.BiConsumer`
combiner - an associative, non-interfering, stateless function for combining two values, which must be compatible with the accumulator function - `java.util.function.BiConsumer`
returns: the result of the reduction - `<R> R`countclj
(count this)Returns the count of elements in this stream. This is a special case of a reduction and is equivalent to:
return mapToLong(e -> 1L).sum();
This is a terminal operation.
returns: the count of elements in this stream - long
Returns the count of elements in this stream. This is a special case of
a reduction and is
equivalent to:
return mapToLong(e -> 1L).sum();
This is a terminal operation.
returns: the count of elements in this stream - `long`distinctclj
(distinct this)Returns a stream consisting of the distinct elements (according to Object.equals(Object)) of this stream.
For ordered streams, the selection of distinct elements is stable (for duplicated elements, the element appearing first in the encounter order is preserved.) For unordered streams, no stability guarantees are made.
This is a stateful intermediate operation.
returns: the new stream - java.util.stream.Stream<T>
Returns a stream consisting of the distinct elements (according to Object.equals(Object)) of this stream. For ordered streams, the selection of distinct elements is stable (for duplicated elements, the element appearing first in the encounter order is preserved.) For unordered streams, no stability guarantees are made. This is a stateful intermediate operation. returns: the new stream - `java.util.stream.Stream<T>`
filterclj
(filter this predicate)Returns a stream consisting of the elements of this stream that match the given predicate.
This is an intermediate operation.
predicate - a non-interfering, stateless predicate to apply to each element to determine if it should be included - java.util.function.Predicate
returns: the new stream - java.util.stream.Stream<T>
Returns a stream consisting of the elements of this stream that match the given predicate. This is an intermediate operation. predicate - a non-interfering, stateless predicate to apply to each element to determine if it should be included - `java.util.function.Predicate` returns: the new stream - `java.util.stream.Stream<T>`
find-anyclj
(find-any this)Returns an Optional describing some element of the stream, or an empty Optional if the stream is empty.
This is a short-circuiting terminal operation.
The behavior of this operation is explicitly nondeterministic; it is free to select any element in the stream. This is to allow for maximal performance in parallel operations; the cost is that multiple invocations on the same source may not return the same result. (If a stable result is desired, use findFirst() instead.)
returns: an Optional describing some element of this stream, or an
empty Optional if the stream is empty - java.util.Optional<T>
throws: java.lang.NullPointerException - if the element selected is null
Returns an Optional describing some element of the stream, or an empty Optional if the stream is empty. This is a short-circuiting terminal operation. The behavior of this operation is explicitly nondeterministic; it is free to select any element in the stream. This is to allow for maximal performance in parallel operations; the cost is that multiple invocations on the same source may not return the same result. (If a stable result is desired, use findFirst() instead.) returns: an Optional describing some element of this stream, or an empty Optional if the stream is empty - `java.util.Optional<T>` throws: java.lang.NullPointerException - if the element selected is null
find-firstclj
(find-first this)Returns an Optional describing the first element of this stream, or an empty Optional if the stream is empty. If the stream has no encounter order, then any element may be returned.
This is a short-circuiting terminal operation.
returns: an Optional describing the first element of this stream,
or an empty Optional if the stream is empty - java.util.Optional<T>
throws: java.lang.NullPointerException - if the element selected is null
Returns an Optional describing the first element of this stream, or an empty Optional if the stream is empty. If the stream has no encounter order, then any element may be returned. This is a short-circuiting terminal operation. returns: an Optional describing the first element of this stream, or an empty Optional if the stream is empty - `java.util.Optional<T>` throws: java.lang.NullPointerException - if the element selected is null
flat-mapclj
(flat-map this mapper)Returns a stream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element. Each mapped stream is closed after its contents have been placed into this stream. (If a mapped stream is null an empty stream is used, instead.)
This is an intermediate operation.
mapper - a non-interfering, stateless function to apply to each element which produces a stream of new values - java.util.function.Function
returns: the new stream - <R> java.util.stream.Stream<R>
Returns a stream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element. Each mapped stream is closed after its contents have been placed into this stream. (If a mapped stream is null an empty stream is used, instead.) This is an intermediate operation. mapper - a non-interfering, stateless function to apply to each element which produces a stream of new values - `java.util.function.Function` returns: the new stream - `<R> java.util.stream.Stream<R>`
flat-map-to-doubleclj
(flat-map-to-double this mapper)Returns an DoubleStream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element. Each mapped stream is closed after its contents have placed been into this stream. (If a mapped stream is null an empty stream is used, instead.)
This is an intermediate operation.
mapper - a non-interfering, stateless function to apply to each element which produces a stream of new values - java.util.function.Function
returns: the new stream - java.util.stream.DoubleStream
Returns an DoubleStream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element. Each mapped stream is closed after its contents have placed been into this stream. (If a mapped stream is null an empty stream is used, instead.) This is an intermediate operation. mapper - a non-interfering, stateless function to apply to each element which produces a stream of new values - `java.util.function.Function` returns: the new stream - `java.util.stream.DoubleStream`
flat-map-to-intclj
(flat-map-to-int this mapper)Returns an IntStream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element. Each mapped stream is closed after its contents have been placed into this stream. (If a mapped stream is null an empty stream is used, instead.)
This is an intermediate operation.
mapper - a non-interfering, stateless function to apply to each element which produces a stream of new values - java.util.function.Function
returns: the new stream - java.util.stream.IntStream
Returns an IntStream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element. Each mapped stream is closed after its contents have been placed into this stream. (If a mapped stream is null an empty stream is used, instead.) This is an intermediate operation. mapper - a non-interfering, stateless function to apply to each element which produces a stream of new values - `java.util.function.Function` returns: the new stream - `java.util.stream.IntStream`
flat-map-to-longclj
(flat-map-to-long this mapper)Returns an LongStream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element. Each mapped stream is closed after its contents have been placed into this stream. (If a mapped stream is null an empty stream is used, instead.)
This is an intermediate operation.
mapper - a non-interfering, stateless function to apply to each element which produces a stream of new values - java.util.function.Function
returns: the new stream - java.util.stream.LongStream
Returns an LongStream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element. Each mapped stream is closed after its contents have been placed into this stream. (If a mapped stream is null an empty stream is used, instead.) This is an intermediate operation. mapper - a non-interfering, stateless function to apply to each element which produces a stream of new values - `java.util.function.Function` returns: the new stream - `java.util.stream.LongStream`
for-eachclj
(for-each this action)Performs an action for each element of this stream.
This is a terminal operation.
The behavior of this operation is explicitly nondeterministic. For parallel stream pipelines, this operation does not guarantee to respect the encounter order of the stream, as doing so would sacrifice the benefit of parallelism. For any given element, the action may be performed at whatever time and in whatever thread the library chooses. If the action accesses shared state, it is responsible for providing the required synchronization.
action - a non-interfering action to perform on the elements - java.util.function.Consumer
Performs an action for each element of this stream. This is a terminal operation. The behavior of this operation is explicitly nondeterministic. For parallel stream pipelines, this operation does not guarantee to respect the encounter order of the stream, as doing so would sacrifice the benefit of parallelism. For any given element, the action may be performed at whatever time and in whatever thread the library chooses. If the action accesses shared state, it is responsible for providing the required synchronization. action - a non-interfering action to perform on the elements - `java.util.function.Consumer`
for-each-orderedclj
(for-each-ordered this action)Performs an action for each element of this stream, in the encounter order of the stream if the stream has a defined encounter order.
This is a terminal operation.
This operation processes the elements one at a time, in encounter order if one exists. Performing the action for one element happens-before performing the action for subsequent elements, but for any given element, the action may be performed in whatever thread the library chooses.
action - a non-interfering action to perform on the elements - java.util.function.Consumer
Performs an action for each element of this stream, in the encounter order of the stream if the stream has a defined encounter order. This is a terminal operation. This operation processes the elements one at a time, in encounter order if one exists. Performing the action for one element happens-before performing the action for subsequent elements, but for any given element, the action may be performed in whatever thread the library chooses. action - a non-interfering action to perform on the elements - `java.util.function.Consumer`
limitclj
(limit this max-size)Returns a stream consisting of the elements of this stream, truncated to be no longer than maxSize in length.
This is a short-circuiting stateful intermediate operation.
max-size - the number of elements the stream should be limited to - long
returns: the new stream - java.util.stream.Stream<T>
throws: java.lang.IllegalArgumentException - if maxSize is negative
Returns a stream consisting of the elements of this stream, truncated to be no longer than maxSize in length. This is a short-circuiting stateful intermediate operation. max-size - the number of elements the stream should be limited to - `long` returns: the new stream - `java.util.stream.Stream<T>` throws: java.lang.IllegalArgumentException - if maxSize is negative
mapclj
(map this mapper)Returns a stream consisting of the results of applying the given function to the elements of this stream.
This is an intermediate operation.
mapper - a non-interfering, stateless function to apply to each element - java.util.function.Function
returns: the new stream - <R> java.util.stream.Stream<R>
Returns a stream consisting of the results of applying the given function to the elements of this stream. This is an intermediate operation. mapper - a non-interfering, stateless function to apply to each element - `java.util.function.Function` returns: the new stream - `<R> java.util.stream.Stream<R>`
map-to-doubleclj
(map-to-double this mapper)Returns a DoubleStream consisting of the results of applying the given function to the elements of this stream.
This is an intermediate operation.
mapper - a non-interfering, stateless function to apply to each element - java.util.function.ToDoubleFunction
returns: the new stream - java.util.stream.DoubleStream
Returns a DoubleStream consisting of the results of applying the given function to the elements of this stream. This is an intermediate operation. mapper - a non-interfering, stateless function to apply to each element - `java.util.function.ToDoubleFunction` returns: the new stream - `java.util.stream.DoubleStream`
map-to-intclj
(map-to-int this mapper)Returns an IntStream consisting of the results of applying the given function to the elements of this stream.
This is an intermediate operation.
mapper - a non-interfering, stateless function to apply to each element - java.util.function.ToIntFunction
returns: the new stream - java.util.stream.IntStream
Returns an IntStream consisting of the results of applying the
given function to the elements of this stream.
This is an
intermediate operation.
mapper - a non-interfering, stateless function to apply to each element - `java.util.function.ToIntFunction`
returns: the new stream - `java.util.stream.IntStream`map-to-longclj
(map-to-long this mapper)Returns a LongStream consisting of the results of applying the given function to the elements of this stream.
This is an intermediate operation.
mapper - a non-interfering, stateless function to apply to each element - java.util.function.ToLongFunction
returns: the new stream - java.util.stream.LongStream
Returns a LongStream consisting of the results of applying the given function to the elements of this stream. This is an intermediate operation. mapper - a non-interfering, stateless function to apply to each element - `java.util.function.ToLongFunction` returns: the new stream - `java.util.stream.LongStream`
maxclj
(max this comparator)Returns the maximum element of this stream according to the provided Comparator. This is a special case of a reduction.
This is a terminal operation.
comparator - a non-interfering, stateless Comparator to compare elements of this stream - java.util.Comparator
returns: an Optional describing the maximum element of this stream,
or an empty Optional if the stream is empty - java.util.Optional<T>
throws: java.lang.NullPointerException - if the maximum element is null
Returns the maximum element of this stream according to the provided Comparator. This is a special case of a reduction. This is a terminal operation. comparator - a non-interfering, stateless Comparator to compare elements of this stream - `java.util.Comparator` returns: an Optional describing the maximum element of this stream, or an empty Optional if the stream is empty - `java.util.Optional<T>` throws: java.lang.NullPointerException - if the maximum element is null
minclj
(min this comparator)Returns the minimum element of this stream according to the provided Comparator. This is a special case of a reduction.
This is a terminal operation.
comparator - a non-interfering, stateless Comparator to compare elements of this stream - java.util.Comparator
returns: an Optional describing the minimum element of this stream,
or an empty Optional if the stream is empty - java.util.Optional<T>
throws: java.lang.NullPointerException - if the minimum element is null
Returns the minimum element of this stream according to the provided Comparator. This is a special case of a reduction. This is a terminal operation. comparator - a non-interfering, stateless Comparator to compare elements of this stream - `java.util.Comparator` returns: an Optional describing the minimum element of this stream, or an empty Optional if the stream is empty - `java.util.Optional<T>` throws: java.lang.NullPointerException - if the minimum element is null
none-matchclj
(none-match this predicate)Returns whether no elements of this stream match the provided predicate. May not evaluate the predicate on all elements if not necessary for determining the result. If the stream is empty then true is returned and the predicate is not evaluated.
This is a short-circuiting terminal operation.
predicate - a non-interfering, stateless predicate to apply to elements of this stream - java.util.function.Predicate
returns: true if either no elements of the stream match the
provided predicate or the stream is empty, otherwise false - boolean
Returns whether no elements of this stream match the provided predicate. May not evaluate the predicate on all elements if not necessary for determining the result. If the stream is empty then true is returned and the predicate is not evaluated. This is a short-circuiting terminal operation. predicate - a non-interfering, stateless predicate to apply to elements of this stream - `java.util.function.Predicate` returns: true if either no elements of the stream match the provided predicate or the stream is empty, otherwise false - `boolean`
peekclj
(peek this action)Returns a stream consisting of the elements of this stream, additionally performing the provided action on each element as elements are consumed from the resulting stream.
This is an intermediate operation.
For parallel stream pipelines, the action may be called at whatever time and in whatever thread the element is made available by the upstream operation. If the action modifies shared state, it is responsible for providing the required synchronization.
action - a non-interfering action to perform on the elements as they are consumed from the stream - java.util.function.Consumer
returns: the new stream - java.util.stream.Stream<T>
Returns a stream consisting of the elements of this stream, additionally performing the provided action on each element as elements are consumed from the resulting stream. This is an intermediate operation. For parallel stream pipelines, the action may be called at whatever time and in whatever thread the element is made available by the upstream operation. If the action modifies shared state, it is responsible for providing the required synchronization. action - a non-interfering action to perform on the elements as they are consumed from the stream - `java.util.function.Consumer` returns: the new stream - `java.util.stream.Stream<T>`
reduceclj
(reduce this accumulator)(reduce this identity accumulator)(reduce this identity accumulator combiner)Performs a reduction on the elements of this stream, using the provided identity, accumulation and combining functions. This is equivalent to:
U result = identity;
for (T element : this stream)
result = accumulator.apply(result, element)
return result;
but is not constrained to execute sequentially.
The identity value must be an identity for the combiner function. This means that for all u, combiner(identity, u) is equal to u. Additionally, the combiner function must be compatible with the accumulator function; for all u and t, the following must hold:
combiner.apply(u, accumulator.apply(identity, t)) == accumulator.apply(u, t)
This is a terminal operation.
identity - the identity value for the combiner function - U
accumulator - an associative, non-interfering, stateless function for incorporating an additional element into a result - java.util.function.BiFunction
combiner - an associative, non-interfering, stateless function for combining two values, which must be compatible with the accumulator function - java.util.function.BinaryOperator
returns: the result of the reduction - <U> U
Performs a reduction on the
elements of this stream, using the provided identity, accumulation and
combining functions. This is equivalent to:
U result = identity;
for (T element : this stream)
result = accumulator.apply(result, element)
return result;
but is not constrained to execute sequentially.
The identity value must be an identity for the combiner
function. This means that for all u, combiner(identity, u)
is equal to u. Additionally, the combiner function
must be compatible with the accumulator function; for all
u and t, the following must hold:
combiner.apply(u, accumulator.apply(identity, t)) == accumulator.apply(u, t)
This is a terminal
operation.
identity - the identity value for the combiner function - `U`
accumulator - an associative, non-interfering, stateless function for incorporating an additional element into a result - `java.util.function.BiFunction`
combiner - an associative, non-interfering, stateless function for combining two values, which must be compatible with the accumulator function - `java.util.function.BinaryOperator`
returns: the result of the reduction - `<U> U`skipclj
(skip this n)Returns a stream consisting of the remaining elements of this stream after discarding the first n elements of the stream. If this stream contains fewer than n elements then an empty stream will be returned.
This is a stateful intermediate operation.
n - the number of leading elements to skip - long
returns: the new stream - java.util.stream.Stream<T>
throws: java.lang.IllegalArgumentException - if n is negative
Returns a stream consisting of the remaining elements of this stream after discarding the first n elements of the stream. If this stream contains fewer than n elements then an empty stream will be returned. This is a stateful intermediate operation. n - the number of leading elements to skip - `long` returns: the new stream - `java.util.stream.Stream<T>` throws: java.lang.IllegalArgumentException - if n is negative
sortedclj
(sorted this)(sorted this comparator)Returns a stream consisting of the elements of this stream, sorted according to the provided Comparator.
For ordered streams, the sort is stable. For unordered streams, no stability guarantees are made.
This is a stateful intermediate operation.
comparator - a non-interfering, stateless Comparator to be used to compare stream elements - java.util.Comparator
returns: the new stream - java.util.stream.Stream<T>
Returns a stream consisting of the elements of this stream, sorted according to the provided Comparator. For ordered streams, the sort is stable. For unordered streams, no stability guarantees are made. This is a stateful intermediate operation. comparator - a non-interfering, stateless Comparator to be used to compare stream elements - `java.util.Comparator` returns: the new stream - `java.util.stream.Stream<T>`
to-arrayclj
(to-array this)(to-array this generator)Returns an array containing the elements of this stream, using the provided generator function to allocate the returned array, as well as any additional arrays that might be required for a partitioned execution or for resizing.
This is a terminal operation.
generator - a function which produces a new array of the desired type and the provided length - java.util.function.IntFunction
returns: an array containing the elements in this stream - <A> A[]
throws: java.lang.ArrayStoreException - if the runtime type of the array returned from the array generator is not a supertype of the runtime type of every element in this stream
Returns an array containing the elements of this stream, using the provided generator function to allocate the returned array, as well as any additional arrays that might be required for a partitioned execution or for resizing. This is a terminal operation. generator - a function which produces a new array of the desired type and the provided length - `java.util.function.IntFunction` returns: an array containing the elements in this stream - `<A> A[]` throws: java.lang.ArrayStoreException - if the runtime type of the array returned from the array generator is not a supertype of the runtime type of every element in this stream
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