Class Spliterators.AbstractSpliterator<T>

java.lang.Object

java.util.Spliterators.AbstractSpliterator<T>

Type Parameters:: T - the type of elements returned by this Spliterator

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:

Nested Class Summary

Nested classes/interfaces declared in interface Spliterator

Spliterator.OfDouble, Spliterator.OfInt, Spliterator.OfLong, Spliterator.OfPrimitive<T,T_CONS,T_SPLITR>

Modifier and Type	Interface	Description
`static interface`	`Spliterator.OfDouble`	A Spliterator specialized for `double` values.
`static interface`	`Spliterator.OfInt`	A Spliterator specialized for `int` values.
`static interface`	`Spliterator.OfLong`	A Spliterator specialized for `long` values.
`static interface`	`Spliterator.OfPrimitive<T, T_CONS, T_SPLITR extends Spliterator.OfPrimitive<T,T_CONS,T_SPLITR>>`	A Spliterator specialized for primitive values.

Field Summary

Fields declared in interface Spliterator

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

Modifier and Type	Field	Description
`static final int`	`CONCURRENT`	Characteristic value signifying that the element source may be safely concurrently modified (allowing additions, replacements, and/or removals) by multiple threads without external synchronization.
`static final int`	`DISTINCT`	Characteristic value signifying that, for each pair of encountered elements `x, y`, `!x.equals(y)`.
`static final int`	`IMMUTABLE`	Characteristic value signifying that the element source cannot be structurally modified; that is, elements cannot be added, replaced, or removed, so such changes cannot occur during traversal.
`static final int`	`NONNULL`	Characteristic value signifying that the source guarantees that encountered elements will not be `null`.
`static final int`	`ORDERED`	Characteristic value signifying that an encounter order is defined for elements.
`static final int`	`SIZED`	Characteristic value signifying that the value returned from `estimateSize()` prior to traversal or splitting represents a finite size that, in the absence of structural source modification, represents an exact count of the number of elements that would be encountered by a complete traversal.
`static final int`	`SORTED`	Characteristic value signifying that encounter order follows a defined sort order.
`static final int`	`SUBSIZED`	Characteristic value signifying that all Spliterators resulting from `trySplit()` will be both `Spliterator.SIZED` and `Spliterator.SUBSIZED`.

Constructor Summary

AbstractSpliterator(long est,
 int additionalCharacteristics)

Modifier	Constructor	Description
`protected`	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.forEachRemaining(Consumer)` traversal, or returns `Long.MAX_VALUE` if infinite, unknown, or too expensive to compute.
`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 Object

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

Modifier and Type	Method	Description
`protected Object`	`clone()`	Creates and returns a copy of this object.
`boolean`	`equals(Object obj)`	Indicates whether some other object is "equal to" this one.
`protected void`	`finalize()`	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
`final Class<?>`	`getClass()`	Returns the runtime class of this `Object`.
`int`	`hashCode()`	Returns a hash code value for this object.
`final void`	`notify()`	Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()`	Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()`	Returns a string representation of the object.
`final void`	`wait()`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
`final void`	`wait(long timeoutMillis)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis, int nanos)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Methods declared in interface Spliterator

forEachRemaining, getComparator, getExactSizeIfKnown, hasCharacteristics, tryAdvance

Modifier and Type	Method	Description
`default void`	`forEachRemaining(Consumer<? super T> action)`	Performs the given action for each remaining element, sequentially in the current thread, until all elements have been processed or the action throws an exception.
`default Comparator<? super T>`	`getComparator()`	If this Spliterator's source is `Spliterator.SORTED` by a `Comparator`, returns that `Comparator`.
`default long`	`getExactSizeIfKnown()`	Convenience method that returns `Spliterator.estimateSize()` if this Spliterator is `Spliterator.SIZED`, else `-1`.
`default boolean`	`hasCharacteristics(int characteristics)`	Returns `true` if this Spliterator's `Spliterator.characteristics()` contain all of the given characteristics.
`boolean`	`tryAdvance(Consumer<? super T> action)`	If a remaining element exists: performs the given action on it, returning `true`; else returns `false`.

Constructor Details

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 Details

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(Consumer) 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>
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 interface Spliterator<T>
Implementation Requirements:: This implementation returns the characteristics as reported when created.
Returns:: a representation of characteristics

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