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## org.neo4j.helpers.collection
Class IteratorUtil

    java.lang.Object
      org.neo4j.helpers.collection.IteratorUtil

    public abstract class IteratorUtil

extends Object

Contains common functionality regarding `Iterator`s and `Iterable`s.

Constructor Summary
`IteratorUtil()`

Method Summary
`static
`<C extends Collection<T>,T> C`
` | `addToCollection(Iterable<T> iterable, C collection)` Adds all the items in `iterator` to `collection`.
`static
`<C extends Collection<T>,T> C`
` | `addToCollection(Iterator<T> iterator, C collection)` Adds all the items in `iterator` to `collection`.
`static
`<T> Collection<T>`
` | `asCollection(Iterable<T> iterable)` Creates a collection from an iterable.
`static
`<T> Iterable<T>`
` | `asIterable(Iterator<T> iterator)` Exposes `iterator` as an `Iterable`.
`static
`<T> int`
` | `count(Iterable<T> iterable)` Counts the number of items in the `iterable` by looping through it.
`static
`<T> int`
` | `count(Iterator<T> iterator)` Counts the number of items in the `iterator` by looping through it.
`static
`<T> T`
` | `first(Iterable<T> iterable)` Returns the given iterable's first element.
`static
`<T> T`
` | `first(Iterator<T> iterator)` Returns the given iterator's first element.
`static
`<T> T`
` | `firstOrNull(Iterable<T> iterable)` Returns the given iterable's first element or `null` if no element found.
`static
`<T> T`
` | `firstOrNull(Iterator<T> iterator)` Returns the given iterator's first element or `null` if no element found.
`static
`<T> T`
` | `fromEnd(Iterable<T> iterable, int n)` Returns the iterator's n:th item from the end of the iteration.
`static
`<T> T`
` | `fromEnd(Iterator<T> iterator, int n)` Returns the iterator's n:th item from the end of the iteration.
`static
`<T> T`
` | `fromEndOrNull(Iterable<T> iterable, int countFromEnd)` Returns the iterator's n:th item from the end of the iteration.
`static
`<T> T`
` | `fromEndOrNull(Iterator<T> iterator, int n)` Returns the iterator's n:th item from the end of the iteration.
`static
`<T> T`
` | `last(Iterable<T> iterable)` Returns the given iterable's last element.
`static
`<T> T`
` | `last(Iterator<T> iterator)` Returns the given iterator's last element.
`static
`<T> T`
` | `lastOrNull(Iterable<T> iterable)` Returns the given iterable's last element or `null` if no element found.
`static
`<T> T`
` | `lastOrNull(Iterator<T> iterator)` Returns the given iterator's last element or `null` if no element found.
`static
`<T> T`
` | `single(Iterable<T> iterable)` Returns the given iterable's single element.
`static
`<T> T`
` | `single(Iterator<T> iterator)` Returns the given iterator's single element.
`static
`<T> T`
` | `singleOrNull(Iterable<T> iterable)` Returns the given iterable's single element or `null` if no element found.
`static
`<T> T`
` | `singleOrNull(Iterator<T> iterator)` Returns the given iterator's single element or `null` if no element found.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### IteratorUtil

    public IteratorUtil()

Method Detail

### firstOrNull

    public static <T> T firstOrNull(Iterator<T> iterator)

  Returns the given iterator's first element or `null` if no element found.

  Type Parameters:
    `T` - the type of elements in `iterator`.
  Parameters:
    `iterator` - the `Iterator` to get elements from.
  Returns:
    the first element in the `iterator`, or `null` if no element found.

### first

    public static <T> T first(Iterator<T> iterator)

  Returns the given iterator's first element. If no element is found a `NoSuchElementException` is thrown.

  Type Parameters:
    `T` - the type of elements in `iterator`.
  Parameters:
    `iterator` - the `Iterator` to get elements from.
  Returns:
    the first element in the `iterator`.
  Throws:
    `{@link` - NoSuchElementException} if no element found.

### lastOrNull

    public static <T> T lastOrNull(Iterator<T> iterator)

  Returns the given iterator's last element or `null` if no element found.

  Type Parameters:
    `T` - the type of elements in `iterator`.
  Parameters:
    `iterator` - the `Iterator` to get elements from.
  Returns:
    the last element in the `iterator`, or `null` if no element found.

### last

    public static <T> T last(Iterator<T> iterator)

  Returns the given iterator's last element. If no element is found a `NoSuchElementException` is thrown.

  Type Parameters:
    `T` - the type of elements in `iterator`.
  Parameters:
    `iterator` - the `Iterator` to get elements from.
  Returns:
    the last element in the `iterator`.
  Throws:
    `{@link` - NoSuchElementException} if no element found.

### singleOrNull

    public static <T> T singleOrNull(Iterator<T> iterator)

  Returns the given iterator's single element or `null` if no element found. If there is more than one element in the iterator a `NoSuchElementException` will be thrown.

  Type Parameters:
    `T` - the type of elements in `iterator`.
  Parameters:
    `iterator` - the `Iterator` to get elements from.
  Returns:
    the single element in `iterator`, or `null` if no element found.
  Throws:
    `{@link` - NoSuchElementException} if more than one element was found.

### single

    public static <T> T single(Iterator<T> iterator)

  Returns the given iterator's single element. If there are no elements or more than one element in the iterator a `NoSuchElementException` will be thrown.

  Type Parameters:
    `T` - the type of elements in `iterator`.
  Parameters:
    `iterator` - the `Iterator` to get elements from.
  Returns:
    the single element in the `iterator`.
  Throws:
    `{@link` - NoSuchElementException} if there isn't exactly one element.

### fromEnd

    public static <T> T fromEnd(Iterator<T> iterator,
                                int n)

  Returns the iterator's n:th item from the end of the iteration. If the iterator has got less than n-1 items in it `NoSuchElementException` is thrown.

  Type Parameters:
    `T` - the type of elements in `iterator`.
  Parameters:
    `iterator` - the `Iterator` to get elements from.
    `n` - the n:th item from the end to get.
  Returns:
    the iterator's n:th item from the end of the iteration.
  Throws:
    `NoSuchElementException` - if the iterator contains less than n-1 items.

### fromEndOrNull

    public static <T> T fromEndOrNull(Iterator<T> iterator,
                                      int n)

  Returns the iterator's n:th item from the end of the iteration. If the iterator has got less than n-1 items in it `null` is returned.

  Type Parameters:
    `T` - the type of elements in `iterator`.
  Parameters:
    `iterator` - the `Iterator` to get elements from.
    `n` - the n:th item from the end to get.
  Returns:
    the iterator's n:th item from the end of the iteration, or `null` if the iterator doesn't contain that many items.

### firstOrNull

    public static <T> T firstOrNull(Iterable<T> iterable)

  Returns the given iterable's first element or `null` if no element found.

  Type Parameters:
    `T` - the type of elements in `iterable`.
  Parameters:
    `iterable` - the `Iterable` to get elements from.
  Returns:
    the first element in the `iterable`, or `null` if no element found.

### first

    public static <T> T first(Iterable<T> iterable)

  Returns the given iterable's first element. If no element is found a `NoSuchElementException` is thrown.

  Type Parameters:
    `T` - the type of elements in `iterable`.
  Parameters:
    `iterable` - the `Iterable` to get elements from.
  Returns:
    the first element in the `iterable`.
  Throws:
    `{@link` - NoSuchElementException} if no element found.

### lastOrNull

    public static <T> T lastOrNull(Iterable<T> iterable)

  Returns the given iterable's last element or `null` if no element found.

  Type Parameters:
    `T` - the type of elements in `iterable`.
  Parameters:
    `iterable` - the `Iterable` to get elements from.
  Returns:
    the last element in the `iterable`, or `null` if no element found.

### last

    public static <T> T last(Iterable<T> iterable)

  Returns the given iterable's last element. If no element is found a `NoSuchElementException` is thrown.

  Type Parameters:
    `T` - the type of elements in `iterable`.
  Parameters:
    `iterable` - the `Iterable` to get elements from.
  Returns:
    the last element in the `iterable`.
  Throws:
    `{@link` - NoSuchElementException} if no element found.

### singleOrNull

    public static <T> T singleOrNull(Iterable<T> iterable)

  Returns the given iterable's single element or `null` if no element found. If there is more than one element in the iterable a `NoSuchElementException` will be thrown.

  Type Parameters:
    `T` - the type of elements in `iterable`.
  Parameters:
    `iterable` - the `Iterable` to get elements from.
  Returns:
    the single element in `iterable`, or `null` if no element found.
  Throws:
    `{@link` - NoSuchElementException} if more than one element was found.

### single

    public static <T> T single(Iterable<T> iterable)

  Returns the given iterable's single element. If there are no elements or more than one element in the iterable a `NoSuchElementException` will be thrown.

  Type Parameters:
    `T` - the type of elements in `iterable`.
  Parameters:
    `iterable` - the `Iterable` to get elements from.
  Returns:
    the single element in the `iterable`.
  Throws:
    `{@link` - NoSuchElementException} if there isn't exactly one element.

### fromEndOrNull

    public static <T> T fromEndOrNull(Iterable<T> iterable,
                                      int countFromEnd)

  Returns the iterator's n:th item from the end of the iteration. If the iterator has got less than n-1 items in it `null` is returned.

  Type Parameters:
    `T` - the type of elements in `iterator`.
  Parameters:
    `iterable` - the `Iterable` to get elements from.
    `countFromEnd` - the n:th item from the end to get.
  Returns:
    the iterator's n:th item from the end of the iteration, or `null` if the iterator doesn't contain that many items.

### fromEnd

    public static <T> T fromEnd(Iterable<T> iterable,
                                int n)

  Returns the iterator's n:th item from the end of the iteration. If the iterator has got less than n-1 items in it `NoSuchElementException` is thrown.

  Type Parameters:
    `T` - the type of elements in `iterator`.
  Parameters:
    `iterable` - the `Iterable` to get elements from.
    `n` - the n:th item from the end to get.
  Returns:
    the iterator's n:th item from the end of the iteration.
  Throws:
    `NoSuchElementException` - if the iterator contains less than n-1 items.

### addToCollection

    public static <C extends Collection<T>,T> C addToCollection(Iterator<T> iterator,
                                                                C collection)

  Adds all the items in `iterator` to `collection`.

  Type Parameters:
    `C` - the type of `Collection` to add to items to.
    `T` - the type of items in the collection and iterator.
  Parameters:
    `iterator` - the `Iterator` to grab the items from.
    `collection` - the `Collection` to add the items to.
  Returns:
    the `collection` which was passed in, now filled with the items from `iterator`.

### addToCollection

    public static <C extends Collection<T>,T> C addToCollection(Iterable<T> iterable,
                                                                C collection)

  Adds all the items in `iterator` to `collection`.

  Type Parameters:
    `C` - the type of `Collection` to add to items to.
    `T` - the type of items in the collection and iterator.
  Parameters:
    `iterable` - the `Iterator` to grab the items from.
    `collection` - the `Collection` to add the items to.
  Returns:
    the `collection` which was passed in, now filled with the items from `iterator`.

### asIterable

    public static <T> Iterable<T> asIterable(Iterator<T> iterator)

  Exposes `iterator` as an `Iterable`. It breaks the contract of `Iterable` in that it returns the supplied iterator instance for each call to `iterator()` on the returned `Iterable` instance. This method mostly exists to make it easy to use an `Iterator` in a for-loop.

  Type Parameters:
    `T` - the type of items in the iterator.
  Parameters:
    `iterator` - the iterator to expose as an `Iterable`.
  Returns:
    the supplied iterator posing as an `Iterable`.

### count

    public static <T> int count(Iterator<T> iterator)

  Counts the number of items in the `iterator` by looping through it.

  Type Parameters:
    `T` - the type of items in the iterator.
  Parameters:
    `iterator` - the `Iterator` to count items in.
  Returns:
    the number of found in `iterator`.

### count

    public static <T> int count(Iterable<T> iterable)

  Counts the number of items in the `iterable` by looping through it.

  Type Parameters:
    `T` - the type of items in the iterator.
  Parameters:
    `iterable` - the `Iterable` to count items in.
  Returns:
    the number of found in `iterator`.

### asCollection

    public static <T> Collection<T> asCollection(Iterable<T> iterable)

  Creates a collection from an iterable.

  Type Parameters:
    `T` - The generic type of both the iterable and the collection.
  Parameters:
    `iterable` - The iterable to create the collection from.
  Returns:
    a collection containing all items from the iterable.

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