net.ninjacat.smooth.iterators

Class LazyIter<E>

java.lang.Object

net.ninjacat.smooth.iterators.LazyIter<E>

Type Parameters:

E - Type of the elements in the iterator

All Implemented Interfaces:

Iterable<E>

public class LazyIter<E>
extends Object
implements Iterable<E>

Functional style lazy immutable rich iterator

Main difference from standard Iterator is that this iterator allows functions to be applied to the elements. It supports standard operations like filter(Predicate), map(Func) or reduce(Object, Function2) and others.

Most of the methods are lazy, they do not perform any action at the call time, but return either Iterable or Promise.

This is essentially a rich wrapper around Iterator over collection. Standard limitations of iterators apply, like restriction of changing collection during iteration

Method Summary

Modifier and Type	Method and Description
Promise<Boolean>	all(Predicate<E> matcher) Checks if all elements of collection match supplied predicate
Promise<Boolean>	any(Predicate<E> matcher) Checks if any of the elements of collection match supplied predicate
LazyIter<E>	filter(Predicate<E> predicate) Filters out elements of iterable collection based on predicate.
Promise<E>	find(Predicate<E> matcher, E defaultValue) Finds element in collection that matches supplied Predicate
E	head() This method is not lazy
Iterator<E>	iterator() Returns Iterator for the elements in this Iterable
<R> LazyIter<R>	map(Func<R,E> func) Maps all the values in the collection to other values using supplied function.
static <E> LazyIter<E>	of(Collection<E> coll) Constructs new lazy iterable from collection.
static <E> LazyIter<E>	of(E... data) Create new lazy iterable from array, sequence of parameters.
static <E> LazyIter<E>	of(E head, Collection<E> tail)
<R> Promise<R>	reduce(R starting, Function2<R,R,E> f) Folds iterable collection left
LazyIter<E>	tail() This method is not lazy
E[]	toArray(E[] array) Returns an array containing all elements contained in this Iterable.
List<E>	toList() This method is not lazy
Set<E>	toSet() This method is not lazy

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Method Detail

of

public static <E> LazyIter<E> of(Collection<E> coll)

Constructs new lazy iterable from collection. Will create internal copy, so original collection may be changed

Type Parameters:

E - type of collection elements

Parameters:

coll - collection

Returns:

new lazy iterable

of

public static <E> LazyIter<E> of(E head,
                                 Collection<E> tail)

of

public static <E> LazyIter<E> of(E... data)

Create new lazy iterable from array, sequence of parameters.

Type Parameters:

E - type of elements

Parameters:

data - array or varargs

Returns:

new lazy iterable

toList

public List<E> toList()

This method is not lazy

Returns:

List containing all the items from this collection. Returned list is immutable

toSet

public Set<E> toSet()

This method is not lazy

Returns:

Set containing all the items from this collection. Returned list is immutable

toArray

public E[] toArray(E[] array)

Returns an array containing all elements contained in this Iterable. If the specified array is large enough to hold the elements, the specified array is used, otherwise an array of the same type is created. If the specified array is used and is larger than this List, the array element following the collection elements is set to null.

Parameters:

array - the array

Returns:

array of the elements from this iterable.

Throws:

ArrayStoreException - if the type of an element in this List cannot be stored in the type of the specified array.

iterator

public Iterator<E> iterator()

Returns Iterator for the elements in this Iterable

Specified by:

iterator in interface Iterable<E>

Returns:

An Iterator instance.

map

public <R> LazyIter<R> map(Func<R,E> func)

Maps all the values in the collection to other values using supplied function.

This function will not create new collection, instead transformation function will be applied to the next original collection's element during each call to Iterator.next()

Type Parameters:

R - result type

Parameters:

func - mapping function

Returns:

Iterable collection of mapped values

reduce

public <R> Promise<R> reduce(R starting,
                             Function2<R,R,E> f)

Folds iterable collection left

Type Parameters:

R - - type of the resulting value

Parameters:

starting - - initial value of the result

f - - folding function

Returns:

Promise of the value of the left-folded collection

filter

public LazyIter<E> filter(Predicate<E> predicate)

Filters out elements of iterable collection based on predicate. Supplied matcher predicate should return true if the element must be included into resulting collection or false otherwise.

Parameters:

predicate - - function to verify collection element

Returns:

Iterable collection. This function will not create resulting collection immediately, instead next element will be evaluated when requested with Iterator.next()

head

public E head()

This method is not lazy

Returns:

first element of the collection

Throws:

NoSuchElementException - if collection is empty

tail

public LazyIter<E> tail()

This method is not lazy

Returns:

All the elements of the collection except for the first

Throws:

NoSuchElementException - if collection is empty

find

public Promise<E> find(Predicate<E> matcher,
                       E defaultValue)

Finds element in collection that matches supplied Predicate

Parameters:

matcher - Predicate to test collection's elements

defaultValue - default value that will be returned if none of the elements in the collection matches predicate

Returns:

Promise of the element found or of the default value

all

public Promise<Boolean> all(Predicate<E> matcher)

Checks if all elements of collection match supplied predicate

Parameters:

matcher - - Predicate to check elements

Returns:

Promise to return true if all elements match predicate or false otherwise

any

public Promise<Boolean> any(Predicate<E> matcher)

Checks if any of the elements of collection match supplied predicate

Parameters:

matcher - - Predicate to check elements

Returns:

Promise to return true if any of the elements match predicate or false otherwise