Class Spliterators.AbstractSpliterator<T>
- java.lang.Object
-
- java.util.Spliterators.AbstractSpliterator<T>
- All Implemented Interfaces:
Spliterator<T>
- Enclosing class:
- Spliterators
public abstract static class Spliterators.AbstractSpliterator<T> extends Object implements Spliterator<T>
An abstract Spliterator
that implements trySplit
to permit limited parallelism.
An extending class need only implement tryAdvance
. The extending class should override forEachRemaining
if it can provide a more performant implementation.
- API Note:
- This class is a useful aid for creating a spliterator when it is not possible or difficult to efficiently partition elements in a manner allowing balanced parallel computation.
An alternative to using this class, that also permits limited parallelism, is to create a spliterator from an iterator (see
Spliterators.spliterator(Iterator, long, int)
. Depending on the circumstances using an iterator may be easier or more convenient than extending this class, such as when there is already an iterator available to use. - Since:
- 1.8
- See Also:
Spliterators.spliterator(Iterator, long, int)
Nested Class Summary
Nested classes/interfaces declared in interface java.util.Spliterator
Spliterator.OfDouble, Spliterator.OfInt, Spliterator.OfLong, Spliterator.OfPrimitive<T,T_CONS,T_SPLITR extends Spliterator.OfPrimitive<T,T_CONS,T_SPLITR>>
Field Summary
Fields declared in interface java.util.Spliterator
CONCURRENT, DISTINCT, IMMUTABLE, NONNULL, ORDERED, SIZED, SORTED, SUBSIZED
Constructor Summary
Modifier | Constructor | Description |
---|---|---|
protected | AbstractSpliterator(long est,
int additionalCharacteristics) | Creates a spliterator reporting the given estimated size and additionalCharacteristics. |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
int | characteristics() | Returns a set of characteristics of this Spliterator and its elements. |
long | estimateSize() | Returns an estimate of the number of elements that would be encountered by a |
Spliterator<T> | trySplit() | If this spliterator can be partitioned, returns a Spliterator covering elements, that will, upon return from this method, not be covered by this Spliterator. |
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods declared in interface java.util.Spliterator
forEachRemaining, getComparator, getExactSizeIfKnown, hasCharacteristics, tryAdvance
Constructor Detail
AbstractSpliterator
protected AbstractSpliterator(long est, int additionalCharacteristics)
Creates a spliterator reporting the given estimated size and additionalCharacteristics.
- Parameters:
-
est
- the estimated size of this spliterator if known, otherwiseLong.MAX_VALUE
. -
additionalCharacteristics
- properties of this spliterator's source or elements. IfSIZED
is reported then this spliterator will additionally reportSUBSIZED
.
Method Detail
trySplit
public Spliterator<T> trySplit()
If this spliterator can be partitioned, returns a Spliterator covering elements, that will, upon return from this method, not be covered by this Spliterator.
If this Spliterator is Spliterator.ORDERED
, the returned Spliterator must cover a strict prefix of the elements.
Unless this Spliterator covers an infinite number of elements, repeated calls to trySplit()
must eventually return null
. Upon non-null return:
- the value reported for
estimateSize()
before splitting, must, after splitting, be greater than or equal toestimateSize()
for this and the returned Spliterator; and - if this Spliterator is
SUBSIZED
, thenestimateSize()
for this spliterator before splitting must be equal to the sum ofestimateSize()
for this and the returned Spliterator after splitting.
This method may return null
for any reason, including emptiness, inability to split after traversal has commenced, data structure constraints, and efficiency considerations. This implementation permits limited parallelism.
- Specified by:
-
trySplit
in interfaceSpliterator<T>
- Returns:
- a
Spliterator
covering some portion of the elements, ornull
if this spliterator cannot be split
estimateSize
public long estimateSize()
Returns an estimate of the number of elements that would be encountered by a Spliterator.forEachRemaining(java.util.function.Consumer<? super T>)
traversal, or returns Long.MAX_VALUE
if infinite, unknown, or too expensive to compute.
If this Spliterator is Spliterator.SIZED
and has not yet been partially traversed or split, or this Spliterator is Spliterator.SUBSIZED
and has not yet been partially traversed, this estimate must be an accurate count of elements that would be encountered by a complete traversal. Otherwise, this estimate may be arbitrarily inaccurate, but must decrease as specified across invocations of Spliterator.trySplit()
.
- Specified by:
-
estimateSize
in interfaceSpliterator<T>
- Implementation Requirements:
- This implementation returns the estimated size as reported when created and, if the estimate size is known, decreases in size when split.
- Returns:
- the estimated size, or
Long.MAX_VALUE
if infinite, unknown, or too expensive to compute.
characteristics
public int characteristics()
Returns a set of characteristics of this Spliterator and its elements. The result is represented as ORed values from Spliterator.ORDERED
, Spliterator.DISTINCT
, Spliterator.SORTED
, Spliterator.SIZED
, Spliterator.NONNULL
, Spliterator.IMMUTABLE
, Spliterator.CONCURRENT
, Spliterator.SUBSIZED
. Repeated calls to characteristics()
on a given spliterator, prior to or in-between calls to trySplit
, should always return the same result.
If a Spliterator reports an inconsistent set of characteristics (either those returned from a single invocation or across multiple invocations), no guarantees can be made about any computation using this Spliterator.
- Specified by:
-
characteristics
in interfaceSpliterator<T>
- Implementation Requirements:
- This implementation returns the characteristics as reported when created.
- Returns:
- a representation of characteristics