Module org.elasticsearch.server

Package org.elasticsearch.common.collect

Class Iterators

java.lang.Object

org.elasticsearch.common.collect.Iterators

public class Iterators
extends Object

Constructor Summary

Constructors

Constructor	Description
Iterators()

Method Summary

Modifier and Type	Method	Description
static <T> Iterator<T>	concat(Iterator<? extends T>... iterators)
static <T, U> Iterator<U>	enumerate(Iterator<? extends T> input, BiFunction<Integer,T,? extends U> fn)	Enumerates the elements of an iterator together with their index, using a function to combine the pair together into the final items produced by the iterator.
static <T> boolean	equals(Iterator<? extends T> iterator1, Iterator<? extends T> iterator2, BiPredicate<T,T> itemComparer)
static <T> Iterator<T>	failFast(Iterator<T> input, BooleanSupplier isFailingSupplier)	Returns an iterator over the same items as the provided input except that it stops yielding items (i.e.
static <T> Iterator<T>	filter(Iterator<? extends T> input, Predicate<T> predicate)
static <T, U> Iterator<U>	flatMap(Iterator<? extends T> input, Function<T,Iterator<? extends U>> fn)
static <T> Iterator<T>	forArray(T[] array)
static <T> Iterator<T>	forRange(int lowerBoundInclusive, int upperBoundExclusive, IntFunction<? extends T> fn)
static <T> Iterator<T>	fromSupplier(Supplier<? extends T> input)	Adapts a Supplier object into an iterator.
static <T> int	hashCode(Iterator<? extends T> iterator, ToIntFunction<T> itemHashcode)
static <T> Iterator<T>	limit(Iterator<? extends T> input, int n)	Returns an iterator that yields at most the first n elements of the provided input iterator.
static <T, U> Iterator<U>	map(Iterator<? extends T> input, Function<T,? extends U> fn)
static <T> Iterator<T>	single(T element)	Returns a single element iterator over the supplied value.
static <T> List<T>	toList(Iterator<T> iterator)	Returns a list containing the elements of the provided iterator.

Methods inherited from class java.lang.Object

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

Constructor Details

Iterators

public Iterators()

Method Details

single

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

Returns a single element iterator over the supplied value.

concat

@SafeVarargs
public static <T> Iterator<T> concat(Iterator<? extends T>... iterators)

forArray

public static <T> Iterator<T> forArray(T[] array)

forRange

public static <T> Iterator<T> forRange(int lowerBoundInclusive,
 int upperBoundExclusive,
 IntFunction<? extends T> fn)

map

public static <T,
U> Iterator<U> map(Iterator<? extends T> input,
 Function<T,? extends U> fn)

filter

public static <T> Iterator<T> filter(Iterator<? extends T> input,
 Predicate<T> predicate)

Parameters:

input - An iterator over non-null values.

predicate - The predicate with which to filter the input.

Returns:

an iterator which returns the values from input which match predicate.

limit

public static <T> Iterator<T> limit(Iterator<? extends T> input,
 int n)

Returns an iterator that yields at most the first n elements of the provided input iterator.

toList

public static <T> List<T> toList(Iterator<T> iterator)

Returns a list containing the elements of the provided iterator.

flatMap

public static <T,
U> Iterator<U> flatMap(Iterator<? extends T> input,
 Function<T,Iterator<? extends U>> fn)

failFast

public static <T> Iterator<T> failFast(Iterator<T> input,
 BooleanSupplier isFailingSupplier)

Returns an iterator over the same items as the provided input except that it stops yielding items (i.e. starts returning false from Iterator.hasNext() on failure.

enumerate

public static <T,
U> Iterator<U> enumerate(Iterator<? extends T> input,
 BiFunction<Integer,T,? extends U> fn)

Enumerates the elements of an iterator together with their index, using a function to combine the pair together into the final items produced by the iterator.

An example of its usage to enumerate a list of names together with their positional index in the list:

 Iterator<String> nameIterator = ...;
 Iterator<Tuple<Integer, String>> enumeratedNames = Iterators.enumerate(nameIterator, Tuple::new);
 enumeratedNames.forEachRemaining(tuple -> System.out.println("Index: " + t.v1() + ", Name: " + t.v2()));
 

Type Parameters:

T - The object type contained in the original iterator

U - The object type that results from combining the original entry with its index in the iterator

Parameters:

input - The iterator to wrap

fn - A function that takes the index for an entry and the entry itself, returning an item that combines them together

Returns:

An iterator that combines elements together with their indices in the underlying collection

fromSupplier

public static <T> Iterator<T> fromSupplier(Supplier<? extends T> input)

Adapts a Supplier object into an iterator. The resulting iterator will return values from the delegate Supplier until the delegate returns a null value. Once the delegate returns null, the iterator will claim to be empty.

An example of its usage to iterate over a queue while draining it at the same time:

     LinkedList<String> names = ...;
     assert names.size() != 0;

     Iterator<String> nameIterator = Iterator.fromSupplier(names::pollFirst);
     nameIterator.forEachRemaining(System.out::println)
     assert names.size() == 0;
 

Type Parameters:

T - The object type returned from the supplier function

Parameters:

input - A Supplier that returns null when no more elements should be returned from the iterator

Returns:

An iterator that returns elements by calling the supplier until a null value is returned

equals

public static <T> boolean equals(Iterator<? extends T> iterator1,
 Iterator<? extends T> iterator2,
 BiPredicate<T,T> itemComparer)

hashCode

public static <T> int hashCode(Iterator<? extends T> iterator,
 ToIntFunction<T> itemHashcode)