Package io.atlassian.fugue

Class Iterables

java.lang.Object

io.atlassian.fugue.Iterables

public class Iterables
extends java.lang.Object

Contains static utility methods that operate on or return objects of type {code}Iterable{code}. The iterables produced from the functions in this class are safe to reuse multiple times. Iterables#iterator returns a new iterator each time.

Since:

1.0

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
(package private) static class	Iterables.CollectingIterable<A,B>	CollectingIterable, filters and transforms in one.
(package private) static class	Iterables.Cycle<A>
(package private) static class	Iterables.Drop<A>	Iterable that only shows a small range of the original Iterable.
(package private) static class	Iterables.Filter<A>
(package private) static class	Iterables.Intersperse<A>
(package private) static class	Iterables.IterableToString<A>
(package private) static class	Iterables.IteratingIterable<A>	Infinite iterable that repeatedly applies f to start
(package private) static class	Iterables.Join<A>
(package private) static class	Iterables.LazyReference<T>	Class supports the implementation of memoize(Iterable) and is not intended for general use.
(package private) static class	Iterables.Mapped<A,B>
(package private) static class	Iterables.Memoizer<A>	Memoizing iterable, maintains a lazily computed linked list of nodes.
(package private) static class	Iterables.MergeSortedIterable<A>	Merges multiple sorted Iterables into one, sorted iterable.
(package private) static class	Iterables.Take<A>	Iterable that only shows a small range of the original Iterable.
(package private) static class	Iterables.UnfoldingIterable<A,B>	Iterable that repeatedly applies f until it returns none()
(package private) static class	Iterables.Zipper<A,B,C>	Iterable that combines two iterables using a combiner function.

Field Summary

Fields

Modifier and Type	Field	Description
(package private) static java.lang.Iterable<?>	EMPTY

Constructor Summary

Constructors

Modifier	Constructor	Description
private	Iterables()

Method Summary

Modifier and Type	Method	Description
static <A> boolean	addAll(java.util.Collection<A> collectionToModify, java.lang.Iterable<? extends A> elementsToAdd)	Add all the elements of the iterable to the collection
static <A> boolean	all(java.lang.Iterable<? extends A> as, java.util.function.Predicate<? super A> p)	Check if all elements in the input iterable match the input predicate
static <A> boolean	any(java.lang.Iterable<? extends A> as, java.util.function.Predicate<? super A> p)	Check if the iterable contains any elements that match the predicate.
static <A,B> java.lang.Iterable<B>	ap(java.lang.Iterable<A> as, java.lang.Iterable<java.util.function.Function<A,B>> fs)	Performs function application within an iterable (applicative functor pattern).
static <A,B> java.lang.Iterable<B>	collect(java.lang.Iterable<? extends A> from, java.util.function.Function<? super A,Option<B>> partial)	Filters and maps (aka transforms) the unfiltered iterable.
static <T,A,R> R	collect(java.lang.Iterable<T> elements, java.util.stream.Collector<T,A,R> collector)	Uses a Collector to collect/reduce an Iterable.
static <A> java.lang.Iterable<A>	concat(java.lang.Iterable<? extends A>... as)	Concatenate a series of iterables into a single iterable.
static <A> int	count(java.lang.Iterable<A> as, java.util.function.Predicate<? super A> p)	Return the size of the elements inside an iterable that meets a specified predicate.
static <A> java.lang.Iterable<A>	cycle(A... as)	Return an infinite iterable that cycles through the input values in order in a loop.
static <A> java.lang.Iterable<A>	cycle(java.lang.Iterable<? extends A> as)	Return an infinite iterable that cycles through the input values in order in a loop.
static <A> java.lang.Iterable<A>	drop(int n, java.lang.Iterable<A> as)	Drop the first n as and return the rest.
static <A> java.lang.Iterable<A>	dropWhile(java.lang.Iterable<A> as, java.util.function.Predicate<A> p)	Drop elements of as until an element returns false for p#test
static <T> java.lang.Iterable<T>	emptyIterable()	Returns an empty iterable, that is, an Iterable with an Iterator for which hasNext() always returns false, and the other methods throw appropriate exceptions if called.
static <A> java.lang.Iterable<A>	filter(java.lang.Iterable<A> as, java.util.function.Predicate<? super A> p)	Remove elements from the input iterable for which the predicate returns false
static <T> Option<T>	findFirst(java.lang.Iterable<? extends T> elements, java.util.function.Predicate<? super T> p)	Finds the first item that matches the predicate.
static <A> java.util.function.Function<java.lang.Iterable<A>,Option<A>>	findFirst(java.util.function.Predicate<? super A> predicate)	Partial application of the predicate argument to findFirst(Iterable, Predicate) returning a function that takes an Iterable as its argument
static <A> Option<A>	first(java.lang.Iterable<A> as)	If as is empty, returns none().
static <A,B> java.lang.Iterable<B>	flatMap(java.lang.Iterable<A> collection, java.util.function.Function<? super A,? extends java.lang.Iterable<? extends B>> f)	Applies f to each element of collection, then concatenates the result.
static <T,R> R	foldLeft(java.lang.Iterable<T> elements, java.util.function.BiFunction<? super R,? super T,? extends R> foldFunction, R initial)	Folds the Iterable elements into the value of potentially another type.
static <A> java.lang.Iterable<A>	intersperse(java.lang.Iterable<? extends A> as, A a)	Intersperse an element between all the elements in an iterable.
static <A> java.lang.Iterable<A>	intersperse(java.lang.Iterable<? extends A> as, java.util.function.Supplier<A> a)	Intersperse an element between all the elements in an iterable.
static java.util.function.Predicate<java.lang.Iterable<?>>	isEmpty()	Predicate that checks if an iterable is empty.
static <A> java.lang.Iterable<A>	iterable(A... as)	Creates an Iterable from the underlying array of elements.
static <A> java.lang.Iterable<A>	iterate(java.util.function.Function<? super A,? extends A> f, A start)	Returns an infinite Iterable constructed by applying the given iteration function starting at the given value.
static <A> java.lang.Iterable<A>	join(java.lang.Iterable<? extends java.lang.Iterable<? extends A>> ias)	Join Iterable<Iterable<A>> down to Iterable<A>.
static <A> java.lang.String	makeString(java.lang.Iterable<? extends A> as, java.lang.String start, java.lang.String sep, java.lang.String end)	Pretty print an Iterable.
static <A> java.lang.String	makeString(java.lang.Iterable<? extends A> as, java.lang.String start, java.lang.String sep, java.lang.String end, int maxLength)	Pretty print an Iterable.
static <A,B> java.lang.Iterable<B>	map(java.lang.Iterable<A> as, java.util.function.Function<? super A,? extends B> f)	Apply the input function to each of the elements of the input iterable returning a new iterable
static <A> java.lang.Iterable<A>	memoize(java.lang.Iterable<A> xs)	Makes a lazy copy of xs.
static <A extends java.lang.Comparable<A>> java.lang.Iterable<A>	mergeSorted(java.lang.Iterable<? extends java.lang.Iterable<A>> xss)	Merge a number of already sorted collections of elements into a single collection of elements, using the elements natural ordering.
static <A> java.lang.Iterable<A>	mergeSorted(java.lang.Iterable<? extends java.lang.Iterable<A>> xss, java.util.Comparator<A> ordering)	Merge a number of already sorted collections of elements into a single collection of elements.
static <A> Pair<java.lang.Iterable<A>,java.lang.Iterable<A>>	partition(java.lang.Iterable<A> iterable, java.util.function.Predicate<? super A> p)	Filter an Iterable into a Pair of Iterable's.
static java.lang.Iterable<java.lang.Integer>	rangeTo(int start, int end)	Creates a sequence of integers from start up to and including end.
static java.lang.Iterable<java.lang.Integer>	rangeTo(int start, int end, int step)	Creates a sequence of integers from start up to and including end with the the supplied step between them.
static java.lang.Iterable<java.lang.Integer>	rangeUntil(int start, int end)	Creates a sequence of integers from start up to but not including end.
static java.lang.Iterable<java.lang.Integer>	rangeUntil(int start, int end, int step)	Creates a sequence of integers from start up to but not including end with the the supplied step between them.
static <A,B> java.lang.Iterable<B>	revMap(java.lang.Iterable<? extends java.util.function.Function<A,B>> fs, A arg)	Applies each function in fs to arg.
static <A> int	size(java.lang.Iterable<A> as)	Return the size of an iterable.
static <A> java.lang.Iterable<A>	take(int n, java.lang.Iterable<A> as)	Aakes the first n as and returns them.
static <A> java.lang.Iterable<A>	takeWhile(java.lang.Iterable<A> as, java.util.function.Predicate<A> p)	Return a new iterable containing only the first elements of as for which p#test returns true.
static <A,B> java.lang.Iterable<B>	transform(java.lang.Iterable<A> as, java.util.function.Function<? super A,? extends B> f)	Deprecated. function provided to make migration easier prefer to use #map where possible
static <A,B> java.lang.Iterable<A>	unfold(java.util.function.Function<? super B,Option<Pair<A,B>>> f, B seed)	Builds an Iterable from a seed value until f returns none() .
static <A,B> Pair<java.lang.Iterable<A>,java.lang.Iterable<B>>	unzip(java.lang.Iterable<Pair<A,B>> pairs)	Unzips an iterable of pairs into a pair of iterables.
static <A,B> java.lang.Iterable<Pair<A,B>>	zip(java.lang.Iterable<A> as, java.lang.Iterable<B> bs)	Zips two iterables into a single iterable that produces pairs.
static <A,B,C> java.util.function.BiFunction<java.lang.Iterable<A>,java.lang.Iterable<B>,java.lang.Iterable<C>>	zipWith(java.util.function.BiFunction<A,B,C> f)	Takes a two-arg function that returns a third type and reurn a new function that takes iterables of the two input types and combines them into a new iterable.
static <A> java.lang.Iterable<Pair<A,java.lang.Integer>>	zipWithIndex(java.lang.Iterable<A> as)	Takes an Iterable, and returns an Iterable of a Pair of the original element and its index starting at zero.

Methods inherited from class java.lang.Object

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

Field Detail

EMPTY

static final java.lang.Iterable<?> EMPTY

Constructor Detail

Iterables

private Iterables()

Method Detail

emptyIterable

public static <T> java.lang.Iterable<T> emptyIterable()

Returns an empty iterable, that is, an Iterable with an Iterator for which hasNext() always returns false, and the other methods throw appropriate exceptions if called. Intended to be used as a more idiomatic replacement for Collections.emptyList() in code that otherwise deals only with iterables.

Type Parameters:

T - the type

Returns:

an empty iterable

Since:

1.2

iterable

@SafeVarargs
public static <A> java.lang.Iterable<A> iterable(A... as)

Creates an Iterable from the underlying array of elements.

Type Parameters:

A - The type of the elements

Parameters:

as - the elements to iterate over

Returns:

an Iterable across the underlying elements

Since:

2.3

findFirst

public static <T> Option<T> findFirst(java.lang.Iterable<? extends T> elements,
                                      java.util.function.Predicate<? super T> p)

Finds the first item that matches the predicate. Traditionally, this should be named find; in this case it is named findFirst to avoid clashing with static imports from Guava's com.google.common.collect.Iterables.

Type Parameters:

T - the type

Parameters:

elements - the iterable to search for a matching element

p - the predicate to use to determine if an element is eligible to be returned

Returns:

the first item in elements that matches predicate

Since:

1.0

findFirst

public static <A> java.util.function.Function<java.lang.Iterable<A>,Option<A>> findFirst(java.util.function.Predicate<? super A> predicate)

Partial application of the predicate argument to findFirst(Iterable, Predicate) returning a function that takes an Iterable as its argument

Type Parameters:

A - the type

Parameters:

predicate - the predicate to use to determine if an element is eligible to be returned

Returns:

a Function that takes an Iterable as its argument, and returns the first element that satisfies the predicate

Since:

2.2

first

public static <A> Option<A> first(java.lang.Iterable<A> as)

If as is empty, returns none(). Otherwise, returns some(get(as, 0)).

Type Parameters:

A - type of elements in as

Parameters:

as - elements to get the first value of, must not be null

Returns:

none() if as is empty. some(get(as, 0)) otherwise

Since:

1.1

ap

public static <A,B> java.lang.Iterable<B> ap(java.lang.Iterable<A> as,
                                                   java.lang.Iterable<java.util.function.Function<A,B>> fs)

Performs function application within an iterable (applicative functor pattern).

Parameters:

as - an iterable

fs - The iterable of functions to apply.

Returns:

A new iterable after applying the given stream of functions through as.

flatMap

public static <A,B> java.lang.Iterable<B> flatMap(java.lang.Iterable<A> collection,
                                                        java.util.function.Function<? super A,? extends java.lang.Iterable<? extends B>> f)

Applies f to each element of collection, then concatenates the result.

Type Parameters:

A - type of elements in collection

B - type elements in the new Iterable f will transform elements to

Parameters:

collection - elements to apply f to

f - Function to apply to elements of collection

Returns:

concatenated result of applying f to each element of collection

Since:

1.1

revMap

public static <A,B> java.lang.Iterable<B> revMap(java.lang.Iterable<? extends java.util.function.Function<A,B>> fs,
                                                       A arg)

Applies each function in fs to arg.

Type Parameters:

A - the argument type

B - the function output and type of the elements of the final iterable.

Parameters:

fs - an iterable of functions that the arg will be applied to

arg - the argument to apply to the functions

Returns:

the results of the functions when applied to the arg

Since:

1.1

isEmpty

public static java.util.function.Predicate<java.lang.Iterable<?>> isEmpty()

Predicate that checks if an iterable is empty.

Returns:

Predicate which checks if an Iterable is empty

Since:

1.1

collect

public static <A,B> java.lang.Iterable<B> collect(java.lang.Iterable<? extends A> from,
                                                        java.util.function.Function<? super A,Option<B>> partial)

Filters and maps (aka transforms) the unfiltered iterable. Applies the given partial function to each element of the unfiltered iterable. If the application returns none, the element will be left out; otherwise, the transformed object contained in the Option will be added to the result.

Type Parameters:

A - the input type

B - the output type

Parameters:

from - the input iterable, must not be null and must not contain null

partial - the collecting function

Returns:

the collected iterable

Since:

2.2

collect

public static <T,A,R> R collect(java.lang.Iterable<T> elements,
                                            java.util.stream.Collector<T,A,R> collector)

Uses a Collector to collect/reduce an Iterable.

Type Parameters:

T - the type of elements in the original Iterable

A - accumulator type

R - return type

Parameters:

elements - the iterable to run the Collector on. Can not be null.

collector - the Collector. Can not be null.

Returns:

the result of the reduction, using the given Collector

Since:

3.1

See Also:

javadocs for more details on how to use Collectors.

foldLeft

public static <T,R> R foldLeft(java.lang.Iterable<T> elements,
                                     java.util.function.BiFunction<? super R,? super T,? extends R> foldFunction,
                                     R initial)

Folds the Iterable elements into the value of potentially another type. Starting the computation with the specified initial value.

Type Parameters:

T - the type of elements in the original Iterable

R - return type

Parameters:

elements - the iterable to run the foldLeft operation on. Can not be null.

foldFunction - the BiFunction used for reducing. Can not be null.

initial - the initial value the folding is started with

Returns:

the result of the reduction, using the given BiFunction

Since:

6.1

partition

public static <A> Pair<java.lang.Iterable<A>,java.lang.Iterable<A>> partition(java.lang.Iterable<A> iterable,
                                                                                    java.util.function.Predicate<? super A> p)

Filter an Iterable into a Pair of Iterable's.

Type Parameters:

A - the type

Parameters:

iterable - to be filtered

p - to filter each element

Returns:

a pair where the left matches the predicate, and the right does not.

Since:

1.2

take

public static <A> java.lang.Iterable<A> take(int n,
                                             java.lang.Iterable<A> as)

Aakes the first n as and returns them.

Type Parameters:

A - type of as

Parameters:

n - number of as to take, must greater than or equal to zero

as - list of values, must not be null and must not contain null

Returns:

first n as

Since:

1.1

drop

public static <A> java.lang.Iterable<A> drop(int n,
                                             java.lang.Iterable<A> as)

Drop the first n as and return the rest.

Type Parameters:

A - type of as

Parameters:

n - number of as to drop, must greater than or equal to zero

as - list of values, must not be null and must not contain null

Returns:

remaining as after dropping the first n

Since:

1.1

dropWhile

public static <A> java.lang.Iterable<A> dropWhile(java.lang.Iterable<A> as,
                                                  java.util.function.Predicate<A> p)

Drop elements of as until an element returns false for p#test

Type Parameters:

A - type of as

Parameters:

as - iterable to remove the first elements of as, must not be null

p - predicate used to test which elements to drop from the iterable, must not be null

Returns:

remaining elements of as after removing the starting elements that for which p#test returns true

Since:

3.0

See Also:

to remove the first n elements

takeWhile

public static <A> java.lang.Iterable<A> takeWhile(java.lang.Iterable<A> as,
                                                  java.util.function.Predicate<A> p)

Return a new iterable containing only the first elements of as for which p#test returns true.

Type Parameters:

A - type of as

Parameters:

as - iterable to source the first elements of as, must not be null

p - predicate used to test which elements to include in the new iterable, must not be null

Returns:

a new iterable containing elements of as starting from the first element of as until p#test returns false

Since:

3.0

See Also:

to take only the first n elements

zip

public static <A,B> java.lang.Iterable<Pair<A,B>> zip(java.lang.Iterable<A> as,
                                                                  java.lang.Iterable<B> bs)

Zips two iterables into a single iterable that produces pairs. See unzip(Iterable) for the opposite operation

Type Parameters:

A - LHS type

B - RHS type

Parameters:

as - left values

bs - right values

Returns:

an iterable of pairs, only as long as the shortest input iterable.

Since:

1.2

zipWith

public static <A,B,C> java.util.function.BiFunction<java.lang.Iterable<A>,java.lang.Iterable<B>,java.lang.Iterable<C>> zipWith(java.util.function.BiFunction<A,B,C> f)

Takes a two-arg function that returns a third type and reurn a new function that takes iterables of the two input types and combines them into a new iterable.

Type Parameters:

A - LHS type

B - RHS type

C - result type

Parameters:

f - combiner function, must not be null

Returns:

an Function that takes two iterables and zips them using the supplied function. The input iterables must not be null and must not contain null

Since:

1.2

zipWithIndex

public static <A> java.lang.Iterable<Pair<A,java.lang.Integer>> zipWithIndex(java.lang.Iterable<A> as)

Takes an Iterable, and returns an Iterable of a Pair of the original element and its index starting at zero.

Type Parameters:

A - the type

Parameters:

as - the original iterable

Returns:

the decorated iterable that generates pairs.

Since:

1.2

unzip

public static <A,B> Pair<java.lang.Iterable<A>,java.lang.Iterable<B>> unzip(java.lang.Iterable<Pair<A,B>> pairs)

Unzips an iterable of pairs into a pair of iterables.

Type Parameters:

A - LHS type

B - RHS type

Parameters:

pairs - the values

Returns:

a pair of iterable of the same length as the input iterable.

Since:

1.2

rangeUntil

public static java.lang.Iterable<java.lang.Integer> rangeUntil(int start,
                                                               int end)

Creates a sequence of integers from start up to but not including end.

Parameters:

start - from (inclusive)

end - to (exclusive)

Returns:

a sequence of integers

Since:

1.2

rangeUntil

public static java.lang.Iterable<java.lang.Integer> rangeUntil(int start,
                                                               int end,
                                                               int step)

Creates a sequence of integers from start up to but not including end with the the supplied step between them.

Parameters:

start - from (inclusive)

end - to (exclusive)

step - size to step – must not be zero, must be positive if end is greater than start, neagtive otherwise

Returns:

a sequence of integers

Since:

1.2

rangeTo

public static java.lang.Iterable<java.lang.Integer> rangeTo(int start,
                                                            int end)

Creates a sequence of integers from start up to and including end.

Parameters:

start - from (inclusive)

end - to (inclusive)

Returns:

a sequence of integers

Since:

1.2

rangeTo

public static java.lang.Iterable<java.lang.Integer> rangeTo(int start,
                                                            int end,
                                                            int step)

Creates a sequence of integers from start up to and including end with the the supplied step between them.

Parameters:

start - from (inclusive), must be greater than zero and less than end

end - to (inclusive)

step - size to step – must not be zero, must be positive if end is greater than start, negative otherwise

Returns:

a sequence of integers

Since:

1.2

intersperse

public static <A> java.lang.Iterable<A> intersperse(java.lang.Iterable<? extends A> as,
                                                    A a)

Intersperse an element between all the elements in an iterable.

Type Parameters:

A - the type of the elements.

Parameters:

as - the source iterable.

a - the element to intersperse between the source elements.

Returns:

a new Iterable that intersperses the element between the source.

Since:

2.3

intersperse

public static <A> java.lang.Iterable<A> intersperse(java.lang.Iterable<? extends A> as,
                                                    java.util.function.Supplier<A> a)

Intersperse an element between all the elements in an iterable.

Type Parameters:

A - the type of the elements.

Parameters:

as - the source iterable.

a - the supplier of elements to intersperse between the source elements.

Returns:

a new Iterable that intersperses the element between the source.

Since:

2.3

size

public static <A> int size(java.lang.Iterable<A> as)

Return the size of an iterable. In most cases this function is required to walk the entire iterable to determine the result. Consider this an O(n) complexity function.

Type Parameters:

A - element type

Parameters:

as - iterable to compute the size of

Returns:

number of elements in the iterable

Since:

3.0

count

public static <A> int count(java.lang.Iterable<A> as,
                            java.util.function.Predicate<? super A> p)

Return the size of the elements inside an iterable that meets a specified predicate.

Type Parameters:

A - element type

Parameters:

as - the source iterable

p - predicate to filter by

Returns:

number of elements in the iterable that meets a prediction

Since:

6.1

transform

@Deprecated
public static <A,B> java.lang.Iterable<B> transform(java.lang.Iterable<A> as,
                                                          java.util.function.Function<? super A,? extends B> f)

Deprecated.

function provided to make migration easier prefer to use #map where possible

Transform an interable by mapping a function across each of its elements

Type Parameters:

A - original iterable type

B - output iterable type

Parameters:

as - the source iterable

f - function to apply to all the elements of as

Returns:

new iterable containing the transformed values produced by f#apply

Since:

3.0

map

public static <A,B> java.lang.Iterable<B> map(java.lang.Iterable<A> as,
                                                    java.util.function.Function<? super A,? extends B> f)

Apply the input function to each of the elements of the input iterable returning a new iterable

Type Parameters:

A - original iterable type

B - output iterable type

Parameters:

as - the source iterable

f - function to apply to all the elements of as

Returns:

new iterable containing values produced by f#apply called on each element

Since:

3.0

filter

public static <A> java.lang.Iterable<A> filter(java.lang.Iterable<A> as,
                                               java.util.function.Predicate<? super A> p)

Remove elements from the input iterable for which the predicate returns false

Type Parameters:

A - element type

Parameters:

as - original iterable

p - predicate to filter by

Returns:

new iterable containing only those elements for which p#test returns true

Since:

3.0

join

public static <A> java.lang.Iterable<A> join(java.lang.Iterable<? extends java.lang.Iterable<? extends A>> ias)

Join Iterable<Iterable<A>> down to Iterable<A>. The resulting iterable will exhaust the first input iterable in order before returning values from the second. Input iterables must not be null and must not contain null.

Type Parameters:

A - element type

Parameters:

ias - one or more iterable to merge into the final iterable result, must not be null and must not return null

Returns:

single level iterable with all the elements of the original iterables

Since:

3.0

concat

@SafeVarargs
public static <A> java.lang.Iterable<A> concat(java.lang.Iterable<? extends A>... as)

Concatenate a series of iterables into a single iterable. Returns an empty iterable if no iterables are supplied. Input iterables must not be null and must not contain null.

Type Parameters:

A - super type of contained by all input iterables

Parameters:

as - any number of iterables containing A

Returns:

new iterable containing all the elements of the input iterables

Since:

3.0

any

public static <A> boolean any(java.lang.Iterable<? extends A> as,
                              java.util.function.Predicate<? super A> p)

Check if the iterable contains any elements that match the predicate.

Type Parameters:

A - type of elements inside the input iterable

Parameters:

as - iterable to compare for matching elements

p - predicate to test for matching elements

Returns:

true if any element in the iterable returns true for the input predicate otherwise false. False for an empty iterable.

Since:

3.0

all

public static <A> boolean all(java.lang.Iterable<? extends A> as,
                              java.util.function.Predicate<? super A> p)

Check if all elements in the input iterable match the input predicate

Type Parameters:

A - type of elements inside the input iterable

Parameters:

as - iterable to compare for matching elements

p - predicate to test for matching elements

Returns:

true if all elements in the iterable return true for the input predicate otherwise false. True for an empty iterable.

Since:

3.0

iterate

public static <A> java.lang.Iterable<A> iterate(java.util.function.Function<? super A,? extends A> f,
                                                A start)

Returns an infinite Iterable constructed by applying the given iteration function starting at the given value.

Type Parameters:

A - type of the elements

Parameters:

f - The iteration function, must not return null

start - The value to begin iterating from.

Returns:

An infinite Iterable of repeated applications of f to start.

Since:

2.4

unfold

public static <A,B> java.lang.Iterable<A> unfold(java.util.function.Function<? super B,Option<Pair<A,B>>> f,
                                                       B seed)

Builds an Iterable from a seed value until f returns none() .

Type Parameters:

A - type of the returned elements.

B - type of the elements for which f is applied.

Parameters:

f - The function that returns some(pair(a, b)), in which case a is the next element of the resulting Iterable and b is used as the input value for the next call of f, or none() if it is done producing the elements. f must not be null and must not return a pair containing null.

seed - The start value to begin the unfold.

Returns:

An Iterable that is a result of unfolding.

Since:

2.4

mergeSorted

public static <A extends java.lang.Comparable<A>> java.lang.Iterable<A> mergeSorted(java.lang.Iterable<? extends java.lang.Iterable<A>> xss)

Merge a number of already sorted collections of elements into a single collection of elements, using the elements natural ordering.

Type Parameters:

A - collection type

Parameters:

xss - collection of already sorted collections, must not be null and must not return null

Returns:

xss merged in a sorted order

Since:

1.1

mergeSorted

public static <A> java.lang.Iterable<A> mergeSorted(java.lang.Iterable<? extends java.lang.Iterable<A>> xss,
                                                    java.util.Comparator<A> ordering)

Merge a number of already sorted collections of elements into a single collection of elements.

Type Parameters:

A - type of the elements

Parameters:

xss - already sorted collection of collections, must not be null and must not return null

ordering - ordering to use when comparing elements, must not be null

Returns:

xss merged in a sorted order

Since:

1.1

addAll

public static <A> boolean addAll(java.util.Collection<A> collectionToModify,
                                 java.lang.Iterable<? extends A> elementsToAdd)

Add all the elements of the iterable to the collection

Type Parameters:

A - element type

Parameters:

collectionToModify - collection to add elements to

elementsToAdd - source of addtional elements

Returns:

true if the collectionToModify was changed

Since:

3.0

cycle

@SafeVarargs
public static <A> java.lang.Iterable<A> cycle(A... as)

Return an infinite iterable that cycles through the input values in order in a loop. If no elements are provided returns an empty iterable. Does not support element removal via Iterator#remove.

Type Parameters:

A - returned elements

Parameters:

as - input values to cycle through

Returns:

an infinite iterable containing the original elements

Since:

3.0

cycle

public static <A> java.lang.Iterable<A> cycle(java.lang.Iterable<? extends A> as)

Return an infinite iterable that cycles through the input values in order in a loop. If no elements are provided returns an empty iterable. Does not support element removal via Iterator#remove.

Type Parameters:

A - returned elements

Parameters:

as - input values to cycle through must not be null

Returns:

an infinite iterable containing the original elements

Since:

3.0

makeString

public static <A> java.lang.String makeString(java.lang.Iterable<? extends A> as,
                                              java.lang.String start,
                                              java.lang.String sep,
                                              java.lang.String end,
                                              int maxLength)

Pretty print an Iterable. Printing following this pattern: <start><element><sep><element><end> If the iterable would result in a String with length more than maxLength printing follows this pattern: <start><element><sep><element>...<end>

Type Parameters:

A - type of the elements in the iterable

Parameters:

as - the iterable to print must not be null

start - prefix to start the printing with

sep - separator to use between each element

end - suffic to end the printing with

maxLength - limit the length of the resulting string

Returns:

a pretty printed copy of the input iterable

Since:

3.0

makeString

public static <A> java.lang.String makeString(java.lang.Iterable<? extends A> as,
                                              java.lang.String start,
                                              java.lang.String sep,
                                              java.lang.String end)

Pretty print an Iterable. Printing following this pattern: <start><element><sep><element><end> If the iterable would result in a String with length more than 100 characters printing follows this pattern: <start><element><sep><element>...<end>

Type Parameters:

A - type of the elements in the iterable

Parameters:

as - the iterable to print must not be null

start - prefix to start the printing with

sep - separator to use between each element

end - suffic to end the printing with

Returns:

a pretty printed copy of the input iterable

Since:

3.0

See Also:

pretty print iterable with a custom length

memoize

public static <A> java.lang.Iterable<A> memoize(java.lang.Iterable<A> xs)

Makes a lazy copy of xs.

Type Parameters:

A - type of elements in xs

Parameters:

xs - Iterable to be memoized

Returns:

lazy copy of as

Since:

1.1