# Class Spliterators.AbstractDoubleSpliterator

java.lang.Object
java.util.Spliterators.AbstractDoubleSpliterator

All Implemented Interfaces:
  `Spliterator<Double>, Spliterator.OfDouble, Spliterator.OfPrimitive<Double, DoubleConsumer, Spliterator.OfDouble>`

Enclosing class:
  `Spliterators`

public abstract static class Spliterators.AbstractDoubleSpliterator extends Object implements Spliterator.OfDouble
An abstract `Spliterator.OfDouble` that implements `trySplit` to permit limited parallelism.

To implement a spliterator 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(java.util.PrimitiveIterator.OfDouble, 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.OfDouble, long, int)`

- ## 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

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

- ## 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.OfDouble`
  `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

  `getComparator, getExactSizeIfKnown, hasCharacteristics`
  Modifier and Type
  Method
  Description
  `default Comparator<? super Double>`
  `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.

  ### Methods declared in interface Spliterator.OfDouble

  `forEachRemaining, tryAdvance`
  Modifier and Type
  Method
  Description
  `default void`
  `forEachRemaining(Consumer<? super Double> 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 boolean`
  `tryAdvance(Consumer<? super Double> action)`
  If a remaining element exists: performs the given action on it, returning `true`; else returns `false`.

  ### Methods declared in interface Spliterator.OfPrimitive

  `forEachRemaining, tryAdvance`
  Modifier and Type
  Method
  Description
  `default void`
  `forEachRemaining(DoubleConsumer 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.
  `boolean`
  `tryAdvance(DoubleConsumer action)`
  If a remaining element exists, performs the given action on it, returning `true`; else returns `false`.

- ## Constructor Details

  - ### AbstractDoubleSpliterator

    protected AbstractDoubleSpliterator(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 Details

  - ### trySplit

    public Spliterator.OfDouble 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<Double>`
    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<Double>`
    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<Double>`
    Implementation Requirements:
      This implementation returns the characteristics as reported when created.
    Returns:
      a representation of characteristics