com.landawn.abacus.util

Class Iterators

java.lang.Object

com.landawn.abacus.util.Iterators

public final class Iterators
extends Object

This is a utility class mostly for Iterator.

The methods in this class should only read the input Collection/Array/Iterator parameters, not modify them.

See Also:

N, Iterables, Maps, StringUtil

Method Summary

Modifier and Type	Method and Description
static long	advance(Iterator<?> iterator, long numberToAdvance) Note: copied from Google Guava under Apache license v2 Calls next() on iterator, either numberToAdvance times or until hasNext() returns false, whichever comes first.
static <A,B> BiIterator<A,B>	concat(BiIterator<A,B>... a)
static <T> ObjIterator<T>	concat(Collection<? extends Iterator<? extends T>> c)
static <T> ObjIterator<T>	concat(Collection<? extends T>... a)
static <T> ObjIterator<T>	concat(Iterator<? extends T>... a)
static <K,V> ObjIterator<Map.Entry<K,V>>	concat(Map<? extends K,? extends V>... a)
static <T> ObjIterator<T>	concat(T[]... a)
static <T> ObjIterator<T>	concatt(Collection<? extends Collection<? extends T>> c)
static long	count(Iterator<?> iter)
static <T,E extends Exception> long	count(Iterator<? extends T> iter, Throwables.Predicate<? super T,E> filter)
static <T> ObjIterator<T>	distinct(Iterator<? extends T> iter)
static <T> ObjIterator<T>	distinctBy(Iterator<? extends T> iter, Function<? super T,?> keyMapper)
static <T> ObjIterator<T>	dropWhile(Iterator<? extends T> iter, Predicate<? super T> filter)
static <T> ObjIterator<T>	filter(Iterator<? extends T> iter, Predicate<? super T> filter)
static <T,U> ObjIterator<U>	flatMap(Iterator<? extends T> iter, Function<? super T,? extends Collection<? extends U>> mapper)
static <T,U> ObjIterator<U>	flattMap(Iterator<? extends T> iter, Function<? super T,? extends U[]> mapper)
static <T,U> ObjIterator<T>	generate(U init, BiPredicate<? super U,T> hasNext, BiFunction<? super U,T,T> supplier)
static <T,U> ObjIterator<T>	generate(U init, Predicate<? super U> hasNext, Function<? super U,T> supplier)
static <T> u.Nullable<T>	get(Iterator<? extends T> iter, long index)
static <T> ObjIterator<T>	limit(Iterator<? extends T> iter, long count) Returns a new Iterator.
static <T,U> ObjIterator<U>	map(Iterator<? extends T> iter, Function<? super T,U> mapper)
static <T> ObjIterator<T>	merge(Collection<? extends Iterator<? extends T>> c, BiFunction<? super T,? super T,MergeResult> nextSelector)
static <T> ObjIterator<T>	merge(Collection<? extends T> a, Collection<? extends T> b, BiFunction<? super T,? super T,MergeResult> nextSelector)
static <T> ObjIterator<T>	merge(Iterator<? extends T> a, Iterator<? extends T> b, BiFunction<? super T,? super T,MergeResult> nextSelector)
static <T> ObjIterator<T>	merge(List<? extends Collection<? extends T>> c, BiFunction<? super T,? super T,MergeResult> nextSelector)
static <T extends Comparable> ObjIterator<T>	mergeSorted(Collection<? extends T> a, Collection<? extends T> b)
static <T> ObjIterator<T>	mergeSorted(Collection<? extends T> a, Collection<? extends T> b, Comparator<? super T> cmp)
static <T extends Comparable> ObjIterator<T>	mergeSorted(Iterator<? extends T> a, Iterator<? extends T> b)
static <T> ObjIterator<T>	mergeSorted(Iterator<? extends T> a, Iterator<? extends T> b, Comparator<? super T> cmp)
static <T> ObjIterator<T>	mergge(Collection<? extends Collection<? extends T>> c, BiFunction<? super T,? super T,MergeResult> nextSelector)
static <T> ObjIterator<T>	repeat(T e, int n)
static <T> ObjIterator<T>	repeatAll(Collection<? extends T> c, int n)
static <T> ObjIterator<T>	repeatAllToSize(Collection<? extends T> c, int size) Repeat all to size.
static <T> ObjIterator<T>	repeatEach(Collection<? extends T> c, int n)
static <T> ObjIterator<T>	repeatEachToSize(Collection<? extends T> c, int size) Repeat each to size.
static <T> ObjIterator<T>	skip(Iterator<? extends T> iter, long n) Calls next() on iterator, either n times or until hasNext() returns false, whichever comes first.
static <T> ObjIterator<T>	skipAndLimit(Iterator<? extends T> iter, long offset, long count) Calls next() on iterator, either offset times or until hasNext() returns false, whichever comes first.
static <T> ObjIterator<T>	skipNull(Iterator<? extends T> iter) Returns a new ObjIterator with null elements removed.
static <T> ObjIterator<T>	skipUntil(Iterator<? extends T> iter, Predicate<? super T> filter)
static <T> ObjIterator<T>	takeWhile(Iterator<? extends T> iter, Predicate<? super T> filter)
static <T> ObjIterator<T>	takeWhileInclusive(Iterator<? extends T> iter, Predicate<? super T> filter)
static <T,L,R> BiIterator<L,R>	unzip(Collection<? extends T> c, BiConsumer<? super T,Pair<L,R>> unzip)
static <T,L,R> BiIterator<L,R>	unzip(Iterator<? extends T> iter, BiConsumer<? super T,Pair<L,R>> unzip)
static <A,B,R> ObjIterator<R>	zip(Collection<A> a, Collection<B> b, A valueForNoneA, B valueForNoneB, BiFunction<? super A,? super B,R> zipFunction)
static <A,B,R> ObjIterator<R>	zip(Collection<A> a, Collection<B> b, BiFunction<? super A,? super B,R> zipFunction)
static <A,B,C,R> ObjIterator<R>	zip(Collection<A> a, Collection<B> b, Collection<C> c, A valueForNoneA, B valueForNoneB, C valueForNoneC, TriFunction<? super A,? super B,? super C,R> zipFunction)
static <A,B,C,R> ObjIterator<R>	zip(Collection<A> a, Collection<B> b, Collection<C> c, TriFunction<? super A,? super B,? super C,R> zipFunction)
static <A,B,R> ObjIterator<R>	zip(Iterator<A> a, Iterator<B> b, A valueForNoneA, B valueForNoneB, BiFunction<? super A,? super B,R> zipFunction)
static <A,B,R> ObjIterator<R>	zip(Iterator<A> a, Iterator<B> b, BiFunction<? super A,? super B,R> zipFunction)
static <A,B,C,R> ObjIterator<R>	zip(Iterator<A> a, Iterator<B> b, Iterator<C> c, A valueForNoneA, B valueForNoneB, C valueForNoneC, TriFunction<? super A,? super B,? super C,R> zipFunction)
static <A,B,C,R> ObjIterator<R>	zip(Iterator<A> a, Iterator<B> b, Iterator<C> c, TriFunction<? super A,? super B,? super C,R> zipFunction)

Methods inherited from class java.lang.Object

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

Method Detail

get

public static <T> u.Nullable<T> get(Iterator<? extends T> iter,
                                    long index)

Type Parameters:

T -

Parameters:

iter -

index -

Returns:

count

public static long count(Iterator<?> iter)

Parameters:

iter -

Returns:

count

public static <T,E extends Exception> long count(Iterator<? extends T> iter,
                                                 Throwables.Predicate<? super T,E> filter)
                                          throws E extends Exception

Parameters:

iter -

filter -

Returns:

Throws:

E extends Exception

repeat

public static <T> ObjIterator<T> repeat(T e,
                                        int n)

Type Parameters:

T -

Parameters:

e -

n -

Returns:

repeatEach

public static <T> ObjIterator<T> repeatEach(Collection<? extends T> c,
                                            int n)

Type Parameters:

T -

Parameters:

c -

n -

Returns:

repeatAll

public static <T> ObjIterator<T> repeatAll(Collection<? extends T> c,
                                           int n)

Type Parameters:

T -

Parameters:

c -

n -

Returns:

repeatEachToSize

public static <T> ObjIterator<T> repeatEachToSize(Collection<? extends T> c,
                                                  int size)

Repeat each to size.

Type Parameters:

T -

Parameters:

c -

size -

Returns:

repeatAllToSize

public static <T> ObjIterator<T> repeatAllToSize(Collection<? extends T> c,
                                                 int size)

Repeat all to size.

Type Parameters:

T -

Parameters:

c -

size -

Returns:

concat

@SafeVarargs
public static <T> ObjIterator<T> concat(T[]... a)

Type Parameters:

T -

Parameters:

a -

Returns:

concat

@SafeVarargs
public static <T> ObjIterator<T> concat(Collection<? extends T>... a)

Type Parameters:

T -

Parameters:

a -

Returns:

concat

@SafeVarargs
public static <K,V> ObjIterator<Map.Entry<K,V>> concat(Map<? extends K,? extends V>... a)

Type Parameters:

T -

Parameters:

a -

Returns:

concatt

public static <T> ObjIterator<T> concatt(Collection<? extends Collection<? extends T>> c)

Type Parameters:

T -

Parameters:

c -

Returns:

concat

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

Type Parameters:

T -

Parameters:

a -

Returns:

concat

public static <T> ObjIterator<T> concat(Collection<? extends Iterator<? extends T>> c)

Type Parameters:

T -

Parameters:

c -

Returns:

concat

@SafeVarargs
public static <A,B> BiIterator<A,B> concat(BiIterator<A,B>... a)

Type Parameters:

A -

B -

Parameters:

a -

Returns:

merge

public static <T> ObjIterator<T> merge(Collection<? extends T> a,
                                       Collection<? extends T> b,
                                       BiFunction<? super T,? super T,MergeResult> nextSelector)

Type Parameters:

T -

Parameters:

a -

b -

nextSelector -

Returns:

merge

public static <T> ObjIterator<T> merge(Iterator<? extends T> a,
                                       Iterator<? extends T> b,
                                       BiFunction<? super T,? super T,MergeResult> nextSelector)

Type Parameters:

T -

Parameters:

a -

b -

nextSelector -

Returns:

merge

public static <T> ObjIterator<T> merge(List<? extends Collection<? extends T>> c,
                                       BiFunction<? super T,? super T,MergeResult> nextSelector)

mergge

public static <T> ObjIterator<T> mergge(Collection<? extends Collection<? extends T>> c,
                                        BiFunction<? super T,? super T,MergeResult> nextSelector)

merge

public static <T> ObjIterator<T> merge(Collection<? extends Iterator<? extends T>> c,
                                       BiFunction<? super T,? super T,MergeResult> nextSelector)

Parameters:

c -

nextSelector - first parameter is selected if Nth.FIRST is returned, otherwise the second parameter is selected.

Returns:

mergeSorted

public static <T extends Comparable> ObjIterator<T> mergeSorted(Collection<? extends T> a,
                                                                Collection<? extends T> b)

Type Parameters:

T -

Parameters:

a - should be in non-descending order as this method does not sort its input.

b - should be in non-descending order as this method does not sort its input.

Returns:

mergeSorted

public static <T> ObjIterator<T> mergeSorted(Collection<? extends T> a,
                                             Collection<? extends T> b,
                                             Comparator<? super T> cmp)

Type Parameters:

T -

Parameters:

a - should be in non-descending order as this method does not sort its input.

b - should be in non-descending order as this method does not sort its input.

cmp -

Returns:

mergeSorted

public static <T extends Comparable> ObjIterator<T> mergeSorted(Iterator<? extends T> a,
                                                                Iterator<? extends T> b)

Type Parameters:

T -

Parameters:

a - should be in non-descending order as this method does not sort its input.

b - should be in non-descending order as this method does not sort its input.

Returns:

mergeSorted

public static <T> ObjIterator<T> mergeSorted(Iterator<? extends T> a,
                                             Iterator<? extends T> b,
                                             Comparator<? super T> cmp)

Type Parameters:

T -

Parameters:

a - should be in non-descending order as this method does not sort its input.

b - should be in non-descending order as this method does not sort its input.

cmp -

Returns:

zip

public static <A,B,R> ObjIterator<R> zip(Collection<A> a,
                                         Collection<B> b,
                                         BiFunction<? super A,? super B,R> zipFunction)

Type Parameters:

A -

B -

R -

Parameters:

a -

b -

zipFunction -

Returns:

zip

public static <A,B,R> ObjIterator<R> zip(Iterator<A> a,
                                         Iterator<B> b,
                                         BiFunction<? super A,? super B,R> zipFunction)

Type Parameters:

A -

B -

R -

Parameters:

a -

b -

zipFunction -

Returns:

zip

public static <A,B,C,R> ObjIterator<R> zip(Collection<A> a,
                                           Collection<B> b,
                                           Collection<C> c,
                                           TriFunction<? super A,? super B,? super C,R> zipFunction)

Type Parameters:

A -

B -

C -

R -

Parameters:

a -

b -

c -

zipFunction -

Returns:

zip

public static <A,B,C,R> ObjIterator<R> zip(Iterator<A> a,
                                           Iterator<B> b,
                                           Iterator<C> c,
                                           TriFunction<? super A,? super B,? super C,R> zipFunction)

Type Parameters:

A -

B -

C -

R -

Parameters:

a -

b -

c -

zipFunction -

Returns:

zip

public static <A,B,R> ObjIterator<R> zip(Collection<A> a,
                                         Collection<B> b,
                                         A valueForNoneA,
                                         B valueForNoneB,
                                         BiFunction<? super A,? super B,R> zipFunction)

Type Parameters:

A -

B -

R -

Parameters:

a -

b -

valueForNoneA -

valueForNoneB -

zipFunction -

Returns:

zip

public static <A,B,R> ObjIterator<R> zip(Iterator<A> a,
                                         Iterator<B> b,
                                         A valueForNoneA,
                                         B valueForNoneB,
                                         BiFunction<? super A,? super B,R> zipFunction)

Type Parameters:

A -

B -

R -

Parameters:

a -

b -

valueForNoneA -

valueForNoneB -

zipFunction -

Returns:

zip

public static <A,B,C,R> ObjIterator<R> zip(Collection<A> a,
                                           Collection<B> b,
                                           Collection<C> c,
                                           A valueForNoneA,
                                           B valueForNoneB,
                                           C valueForNoneC,
                                           TriFunction<? super A,? super B,? super C,R> zipFunction)

Type Parameters:

A -

B -

C -

R -

Parameters:

a -

b -

c -

valueForNoneA -

valueForNoneB -

valueForNoneC -

zipFunction -

Returns:

zip

public static <A,B,C,R> ObjIterator<R> zip(Iterator<A> a,
                                           Iterator<B> b,
                                           Iterator<C> c,
                                           A valueForNoneA,
                                           B valueForNoneB,
                                           C valueForNoneC,
                                           TriFunction<? super A,? super B,? super C,R> zipFunction)

Type Parameters:

A -

B -

C -

R -

Parameters:

a -

b -

c -

valueForNoneA -

valueForNoneB -

valueForNoneC -

zipFunction -

Returns:

unzip

public static <T,L,R> BiIterator<L,R> unzip(Iterator<? extends T> iter,
                                            BiConsumer<? super T,Pair<L,R>> unzip)

Type Parameters:

T -

L -

R -

Parameters:

iter -

unzip - the second parameter is an output parameter.

Returns:

unzip

public static <T,L,R> BiIterator<L,R> unzip(Collection<? extends T> c,
                                            BiConsumer<? super T,Pair<L,R>> unzip)

Type Parameters:

T -

L -

R -

Parameters:

c -

unzip - the second parameter is an output parameter.

Returns:

advance

public static long advance(Iterator<?> iterator,
                           long numberToAdvance)

Note: copied from Google Guava under Apache license v2
Calls next() on iterator, either numberToAdvance times or until hasNext() returns false, whichever comes first.

Parameters:

iterator -

numberToAdvance -

Returns:

skip

public static <T> ObjIterator<T> skip(Iterator<? extends T> iter,
                                      long n)

Calls next() on iterator, either n times or until hasNext() returns false, whichever comes first. This is a lazy evaluation operation. The skip action is only triggered when Iterator.hasNext() or Iterator.next() is called.

Type Parameters:

T -

Parameters:

iter -

n -

Returns:

limit

public static <T> ObjIterator<T> limit(Iterator<? extends T> iter,
                                       long count)

Returns a new Iterator.

Type Parameters:

T -

Parameters:

iter -

count -

Returns:

skipAndLimit

public static <T> ObjIterator<T> skipAndLimit(Iterator<? extends T> iter,
                                              long offset,
                                              long count)

Calls next() on iterator, either offset times or until hasNext() returns false, whichever comes first. This is a lazy evaluation operation. The skip action is only triggered when Iterator.hasNext() or Iterator.next() is called.

Type Parameters:

T -

Parameters:

iter -

offset -

count -

Returns:

skipNull

public static <T> ObjIterator<T> skipNull(Iterator<? extends T> iter)

Returns a new ObjIterator with null elements removed.

Type Parameters:

T -

Parameters:

iter -

Returns:

distinct

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

distinctBy

public static <T> ObjIterator<T> distinctBy(Iterator<? extends T> iter,
                                            Function<? super T,?> keyMapper)

filter

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

Type Parameters:

T -

Parameters:

iter -

filter -

Returns:

takeWhile

public static <T> ObjIterator<T> takeWhile(Iterator<? extends T> iter,
                                           Predicate<? super T> filter)

takeWhileInclusive

public static <T> ObjIterator<T> takeWhileInclusive(Iterator<? extends T> iter,
                                                    Predicate<? super T> filter)

dropWhile

public static <T> ObjIterator<T> dropWhile(Iterator<? extends T> iter,
                                           Predicate<? super T> filter)

skipUntil

public static <T> ObjIterator<T> skipUntil(Iterator<? extends T> iter,
                                           Predicate<? super T> filter)

map

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

Type Parameters:

T -

U -

Parameters:

iter -

mapper -

Returns:

flatMap

public static <T,U> ObjIterator<U> flatMap(Iterator<? extends T> iter,
                                           Function<? super T,? extends Collection<? extends U>> mapper)

Type Parameters:

T -

U -

Parameters:

iter -

mapper -

Returns:

flattMap

public static <T,U> ObjIterator<U> flattMap(Iterator<? extends T> iter,
                                            Function<? super T,? extends U[]> mapper)

generate

public static <T,U> ObjIterator<T> generate(U init,
                                            Predicate<? super U> hasNext,
                                            Function<? super U,T> supplier)

Type Parameters:

T -

U -

Parameters:

init -

hasNext -

supplier -

Returns:

generate

public static <T,U> ObjIterator<T> generate(U init,
                                            BiPredicate<? super U,T> hasNext,
                                            BiFunction<? super U,T,T> supplier)

Type Parameters:

T -

U -

Parameters:

init -

hasNext -

supplier -

Returns: