java.util

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 forEach if it can provide a more performant implementation.

Since:

1.8

See Also:

Spliterators.spliterator(Iterator, long, int)

Nested Class Summary

Nested classes/interfaces inherited from 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 inherited from interface java.util.Spliterator

CONCURRENT, DISTINCT, IMMUTABLE, NONNULL, ORDERED, SIZED, SORTED, SUBSIZED

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractSpliterator(long est, int additionalCharacteristics) Creates a spliterator reporting the given estimated size and additionalCharacteristics.

Method Summary

Modifier and Type	Method and Description
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.
int	characteristics() Returns a set of characteristics of this Spliterator and its elements.
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 inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from 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, otherwise Long.MAX_VALUE.

additionalCharacteristics - properties of this spliterator's source or elements. If SIZED is reported then this spliterator will additionally report SUBSIZED.

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 to estimateSize() for this and the returned Spliterator; and
• if this Spliterator is SUBSIZED, then estimateSize() for this spliterator before splitting must be equal to the sum of estimateSize() 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 interface Spliterator<T>

Returns:

a Spliterator covering some portion of the elements, or null 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 interface Spliterator<T>

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 interface Spliterator<T>

Returns:

a representation of characteristics