almost.functional.utils

Class Iterables

java.lang.Object

almost.functional.utils.Iterables

public final class Iterables
extends java.lang.Object

Utility operations on an iterable.

Method Summary

Methods

Modifier and Type	Method and Description
static <T> boolean	any(java.lang.Iterable<T> iterable, Predicate<? super T> predicate) Determine if any element of an iterable matches a given predicate.
static <T> boolean	contains(java.lang.Iterable<T> iterable, T value) Does an iterable contain a value as determined by Object.isEqual(Object, Object).
static <T> java.lang.Iterable<T>	filter(java.lang.Iterable<T> fromIterable, Predicate<? super T> predicate) Create an iterable that filters an existing iterable based on a predicate.
static <T> Optional<T>	find(java.lang.Iterable<? extends T> iterable, Predicate<? super T> predicate) Apply a predicate to an iterable, returning an optional of the first element where the predicate is true, or empty if no true is found.
static <T> void	forEach(java.lang.Iterable<T> iterable, Consumer<? super T> consumer) Accept a consumer for each element of an iterable.
static <E> Optional<E>	get(java.lang.Iterable<E> iterable, int position) Return an optional of an element from a specified position in an iterable.
static <E> java.lang.Iterable<E>	iterable(java.util.Enumeration<E> enumeration) Convert an enumeration to an iterator.
static <E> Optional<E>	last(java.lang.Iterable<E> iterable) Return the last element of an iterable, or empty if the iterable is empty.
static <F,T> java.lang.Iterable<T>	map(java.lang.Iterable<F> fromIterable, Function<? super F,? extends T> function) Create an iterable that maps an existing iterable to a new one by applying a function to each of it's elements.
static <T,R> R	reduce(java.lang.Iterable<T> iterable, R initial, BiFunction<R,? super T,R> accumulator) Perform a reduction of an iterable, using an initial value, and a two argument function.

Methods inherited from class java.lang.Object

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

Method Detail

forEach

public static <T> void forEach(java.lang.Iterable<T> iterable,
               Consumer<? super T> consumer)

Accept a consumer for each element of an iterable.

Type Parameters:

T - the type of the iterable and consumer

Parameters:

consumer - the consumer to accept for each element

iterable - the iterable

reduce

public static <T,R> R reduce(java.lang.Iterable<T> iterable,
             R initial,
             BiFunction<R,? super T,R> accumulator)

Perform a reduction of an iterable, using an initial value, and a two argument function. The function is applied to each element using the last result as the first argument and the element as the second.

Type Parameters:

T - type of the iterable elements and accumulator's second argument

R - type returned by reduce, the accumulator and it's first argument

Parameters:

iterable - the iterable.

initial - the initial value of the first argument.

accumulator - the two argument function.

Returns:

the final result of the function.

Since:

1.5

find

public static <T> Optional<T> find(java.lang.Iterable<? extends T> iterable,
                   Predicate<? super T> predicate)

Apply a predicate to an iterable, returning an optional of the first element where the predicate is true, or empty if no true is found.

Type Parameters:

T - they type of the iterable and predicate

Parameters:

iterable - the iterable to traverse

predicate - the predicate to test

Returns:

an optional of the first element where the predicate is true, or empty if no true is found.

any

public static <T> boolean any(java.lang.Iterable<T> iterable,
              Predicate<? super T> predicate)

Determine if any element of an iterable matches a given predicate.

Type Parameters:

T - the type of the iterable and predicate

Parameters:

iterable - the iterable to traverse

predicate - the predicate to test

Returns:

true if any element matches the predicate, otherwise false.

contains

public static <T> boolean contains(java.lang.Iterable<T> iterable,
                   T value)

Does an iterable contain a value as determined by Object.isEqual(Object, Object).

Type Parameters:

T - the type of the iterable and object

Parameters:

iterable - the iterable

value - the value

Returns:

true if iterable contain a value as determined by Object.isEqual(Object, Object).

map

public static <F,T> java.lang.Iterable<T> map(java.lang.Iterable<F> fromIterable,
                              Function<? super F,? extends T> function)

Create an iterable that maps an existing iterable to a new one by applying a function to each of it's elements.

Type Parameters:

F - the type of the original elements, and the argument to the function

T - the type of the resulting iterable, and the result of the function

Parameters:

fromIterable - the iterable to be transformed

function - the function to apply to the elements

Returns:

an iterable that transforms an existing iterable by applying a function to each or it's elements.

filter

public static <T> java.lang.Iterable<T> filter(java.lang.Iterable<T> fromIterable,
                               Predicate<? super T> predicate)

Create an iterable that filters an existing iterable based on a predicate.

Type Parameters:

T - the type of the elements

Parameters:

fromIterable - Iterable being filtered

predicate - the predicate to base inclusion upon, true cases are included, false excluded

Returns:

iterable of filtered elements

iterable

public static <E> java.lang.Iterable<E> iterable(java.util.Enumeration<E> enumeration)

Convert an enumeration to an iterator.

Type Parameters:

E - type of the enumeration

Parameters:

enumeration - the enumeration to make into an Iterator

Returns:

An Iterable

Throws:

java.lang.NullPointerException - if enumeration is null

get

public static <E> Optional<E> get(java.lang.Iterable<E> iterable,
                  int position)

Return an optional of an element from a specified position in an iterable. If the position is out of bounds an empty optional is returned. Positions start at 0.

Type Parameters:

E - the type of the elements

Parameters:

iterable - the iterable

position - the position

Returns:

an optional from the given position, or empty if out of bounds

Since:

1.7

last

public static <E> Optional<E> last(java.lang.Iterable<E> iterable)

Return the last element of an iterable, or empty if the iterable is empty.

Type Parameters:

E - type of the iterable elements

Parameters:

iterable - the iterable

Returns:

Optional of the last element, or empty if nothing in the iterable