Package net.sourceforge.pmd.util

Class IteratorUtil

java.lang.Object

net.sourceforge.pmd.util.IteratorUtil

public final class IteratorUtil
extends Object

Operations for dealing with Iterators.

Author:

Clément Fournier

Since:

6.11.0

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	IteratorUtil.AbstractIterator<T>	Note, that this iterator doesn't support the remove operation.
static class	IteratorUtil.AbstractPausingIterator<T>

Method Summary

Modifier and Type	Method	Description
static void	advance(Iterator<?> iterator, int n)	Advance n times.
static <T> boolean	allMatch(Iterator<? extends T> iterator, Predicate<? super T> pred)	Returns whether all elements match the predicate.
static <T> boolean	anyMatch(Iterator<? extends T> iterator, Predicate<? super T> pred)	Returns whether some element match the predicate.
static <T> Iterable<T>	asReversed(List<T> lst)
static <T> Iterator<T>	coerceWildcard(Iterator<? extends T> it)	Coerce an iterator with a wildcard.
static <T> Iterator<T>	concat(Iterator<? extends T> as, Iterator<? extends T> bs)
static int	count(Iterator<?> it)	Counts the items in this iterator, exhausting it.
static <T> Iterator<T>	distinct(Iterator<? extends T> iter)
static <T> Iterator<T>	drop(Iterator<? extends T> source, int n)	Produce an iterator whose first element is the nth element of the given source.
static <T> Iterator<@NonNull T>	dropLast(Iterator<? extends @Nullable T> it, int n)	Remove the last n elements of the iterator.
static <T> Iterator<T>	filter(Iterator<? extends T> it, Predicate<? super T> filter)
static <T> Iterator<@NonNull T>	filterNotNull(Iterator<? extends T> it)
static <T,R> Iterator<R>	flatMap(Iterator<? extends T> iter, Function<? super T,? extends @Nullable Iterator<? extends R>> f)
static <R> Iterator<R>	flatMapWithSelf(Iterator<? extends R> iter, Function<? super R,? extends @Nullable Iterator<? extends R>> f)	Like flatMap, but yields each element of the input iterator before yielding the results of the mapper function.
static <T> Iterator<@NonNull T>	generate(@Nullable T seed, Function<? super @NonNull T,? extends @Nullable T> stepper)	Returns an iterator that applies a stepping function to the previous value yielded.
static <T> @Nullable T	getNth(Iterator<? extends T> iterator, int n)	Returns the nth element of this iterator, or null if the iterator is shorter.
static <T> Iterator<T>	iterate(T... elements)
static <T> @Nullable T	last(Iterator<? extends T> iterator)
static <T,R> Iterator<R>	map(Iterator<? extends T> iter, Function<? super T,? extends R> mapper)
static <T,R> Iterable<R>	mapIterator(Iterable<? extends T> iter, Function<? super Iterator<? extends T>,? extends Iterator<R>> mapper)	Apply a transform on the iterator of an iterable.
static <T,R> Iterator<@NonNull R>	mapNotNull(Iterator<? extends T> it, Function<? super T,? extends R> mapper)
static <T> boolean	noneMatch(Iterator<? extends T> iterator, Predicate<? super T> pred)	Returns whether no elements match the predicate.
static <T> Iterator<T>	peek(Iterator<? extends T> iter, Consumer<? super T> action)
static <T> Iterator<T>	reverse(Iterator<T> it)
static <T> Iterator<T>	singletonIterator(T value)
static <T> Iterator<T>	take(Iterator<? extends T> iterator, int n)	Limit the number of elements yielded by this iterator to the given number.
static <T> Iterator<T>	takeWhile(Iterator<T> iter, Predicate<? super T> predicate)
static <T> Iterable<T>	toIterable(Iterator<T> it)
static <T> List<T>	toList(Iterator<? extends T> it)
static <T> List<@NonNull T>	toNonNullList(Iterator<? extends @Nullable T> it)
static <T> Stream<T>	toStream(Iterable<T> iter)
static <T> Stream<T>	toStream(Iterator<? extends T> iter)

Methods inherited from class java.lang.Object

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

Method Detail

takeWhile

public static <T> Iterator<T> takeWhile(Iterator<T> iter,
                                        Predicate<? super T> predicate)

reverse

public static <T> Iterator<T> reverse(Iterator<T> it)

flatMap

public static <T,R> Iterator<R> flatMap(Iterator<? extends T> iter,
                                              Function<? super T,? extends @Nullable Iterator<? extends R>> f)

flatMapWithSelf

public static <R> Iterator<R> flatMapWithSelf(Iterator<? extends R> iter,
                                              Function<? super R,? extends @Nullable Iterator<? extends R>> f)

Like flatMap, but yields each element of the input iterator before yielding the results of the mapper function. Null elements of the input iterator are both yielded by the returned iterator and passed to the stepper. If the stepper returns null, that result is ignored.

filterNotNull

public static <T> Iterator<@NonNull T> filterNotNull(Iterator<? extends T> it)

mapNotNull

public static <T,R> Iterator<@NonNull R> mapNotNull(Iterator<? extends T> it,
                                                          Function<? super T,? extends R> mapper)

filter

public static <T> Iterator<T> filter(Iterator<? extends T> it,
                                     Predicate<? super T> filter)

peek

public static <T> Iterator<T> peek(Iterator<? extends T> iter,
                                   Consumer<? super T> action)

map

public static <T,R> Iterator<R> map(Iterator<? extends T> iter,
                                          Function<? super T,? extends R> mapper)

mapIterator

public static <T,R> Iterable<R> mapIterator(Iterable<? extends T> iter,
                                                  Function<? super Iterator<? extends T>,? extends Iterator<R>> mapper)

Apply a transform on the iterator of an iterable.

iterate

@SafeVarargs
public static <T> Iterator<T> iterate(T... elements)

concat

public static <T> Iterator<T> concat(Iterator<? extends T> as,
                                     Iterator<? extends T> bs)

distinct

public static <T> Iterator<T> distinct(Iterator<? extends T> iter)

toList

public static <T> List<T> toList(Iterator<? extends T> it)

toNonNullList

public static <T> List<@NonNull T> toNonNullList(Iterator<? extends @Nullable T> it)

dropLast

public static <T> Iterator<@NonNull T> dropLast(Iterator<? extends @Nullable T> it,
                                                int n)

Remove the last n elements of the iterator. This uses n elements as a lookahead.

coerceWildcard

public static <T> Iterator<T> coerceWildcard(Iterator<? extends T> it)

Coerce an iterator with a wildcard. This is safe because the Iterator interface is covariant (not ListIterator though).

toIterable

public static <T> Iterable<T> toIterable(Iterator<T> it)

count

public static int count(Iterator<?> it)

Counts the items in this iterator, exhausting it.

last

public static <T> @Nullable T last(Iterator<? extends T> iterator)

getNth

public static <T> @Nullable T getNth(Iterator<? extends T> iterator,
                                     int n)

Returns the nth element of this iterator, or null if the iterator is shorter.

Throws:

IllegalArgumentException - If n is negative

advance

public static void advance(Iterator<?> iterator,
                           int n)

Advance n times.

take

public static <T> Iterator<T> take(Iterator<? extends T> iterator,
                                   int n)

Limit the number of elements yielded by this iterator to the given number.

drop

public static <T> Iterator<T> drop(Iterator<? extends T> source,
                                   int n)

Produce an iterator whose first element is the nth element of the given source.

generate

public static <T> Iterator<@NonNull T> generate(@Nullable T seed,
                                                Function<? super @NonNull T,? extends @Nullable T> stepper)

Returns an iterator that applies a stepping function to the previous value yielded. Iteration stops on the first null value returned by the stepper.

Type Parameters:

T - Type of values

Parameters:

seed - First value. If null then the iterator is empty

stepper - Step function

anyMatch

public static <T> boolean anyMatch(Iterator<? extends T> iterator,
                                   Predicate<? super T> pred)

Returns whether some element match the predicate. If empty then false is returned.

allMatch

public static <T> boolean allMatch(Iterator<? extends T> iterator,
                                   Predicate<? super T> pred)

Returns whether all elements match the predicate. If empty then true is returned.

noneMatch

public static <T> boolean noneMatch(Iterator<? extends T> iterator,
                                    Predicate<? super T> pred)

Returns whether no elements match the predicate. If empty then true is returned.

singletonIterator

public static <T> Iterator<T> singletonIterator(T value)

asReversed

public static <T> Iterable<T> asReversed(List<T> lst)

toStream

public static <T> Stream<T> toStream(Iterator<? extends T> iter)

toStream

public static <T> Stream<T> toStream(Iterable<T> iter)