Spliterators.AbstractLongSpliterator (Java Platform SE 8 )
Keywords: java.util.Spliterators.AbstractLongSpliterator class
Date: 2020-03-26

compact1, compact2, compact3
java.util

## Class Spliterators.AbstractLongSpliterator

- java.lang.Object
- - java.util.Spliterators.AbstractLongSpliterator

- All Implemented Interfaces:
    Spliterator<Long>, Spliterator.OfLong, Spliterator.OfPrimitive<Long,LongConsumer,Spliterator.OfLong>
  Enclosing class:
    Spliterators

      public abstract static class Spliterators.AbstractLongSpliterator
      extends Object
      implements Spliterator.OfLong

  An abstract `Spliterator.OfLong` that implements `trySplit` to permit limited parallelism.

  To implement a spliterator an extending class need only implement `Spliterator.OfLong.tryAdvance(java.util.function.LongConsumer)` tryAdvance}. The extending class should override `Spliterator.OfLong.forEachRemaining(java.util.function.LongConsumer)` forEach} 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(java.util.PrimitiveIterator.OfLong, long, int)`. Depending on the circumstances using an iterator may be easier or more convenient than extending this class. For example, if there is already an iterator available to use then there is no need to extend this class.

  Since:
    1.8
  See Also:
    `Spliterators.spliterator(java.util.PrimitiveIterator.OfLong, 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` | `AbstractLongSpliterator(long est, int additionalCharacteristics)` Creates a spliterator reporting the given estimated size and characteristics.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and 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(java.util.function.Consumer<? super T>)` traversal, or returns `Long.MAX_VALUE` if infinite, unknown, or too expensive to compute.
    `Spliterator.OfLong` | `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.OfLong

      `forEachRemaining, forEachRemaining, tryAdvance, tryAdvance`

    - ### Methods inherited from interface java.util.Spliterator

      `getComparator, getExactSizeIfKnown, hasCharacteristics`

- - ### Constructor Detail

    - #### AbstractLongSpliterator

          protected AbstractLongSpliterator(long est,
                                            int additionalCharacteristics)

      Creates a spliterator reporting the given estimated size and characteristics.
      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.OfLong 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<Long>`
      Specified by:
        `trySplit` in interface `Spliterator.OfLong`
      Specified by:
        `trySplit` in interface `Spliterator.OfPrimitive<Long,LongConsumer,Spliterator.OfLong>`
      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<Long>`
      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<Long>`
      Implementation Requirements:
        This implementation returns the characteristics as reported when created.
      Returns:
        a representation of characteristics

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