Class IteratorUtils
Iterator
 instances. The implementations are provided in the iterators subpackage.- Since:
- 2.1
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Field SummaryFieldsModifier and TypeFieldDescriptionstatic final ResettableIteratorAn iterator over no elements.static final ResettableListIteratorA list iterator over no elements.static final MapIteratorA map iterator over no elements.static final OrderedIteratorAn ordered iterator over no elements.static final OrderedMapIteratorAn ordered map iterator over no elements.
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Method SummaryModifier and TypeMethodDescriptionstatic <E> ResettableIterator<E> arrayIterator(E... array) Gets an iterator over an object array.static <E> ResettableIterator<E> arrayIterator(E[] array, int start) Gets an iterator over the end part of an object array.static <E> ResettableIterator<E> arrayIterator(E[] array, int start, int end) Gets an iterator over part of an object array.static <E> ResettableIterator<E> arrayIterator(Object array) Gets an iterator over an object or primitive array.static <E> ResettableIterator<E> arrayIterator(Object array, int start) Gets an iterator over the end part of an object or primitive array.static <E> ResettableIterator<E> arrayIterator(Object array, int start, int end) Gets an iterator over part of an object or primitive array.static <E> ResettableListIterator<E> arrayListIterator(E... array) Gets a list iterator over an object array.static <E> ResettableListIterator<E> arrayListIterator(E[] array, int start) Gets a list iterator over the end part of an object array.static <E> ResettableListIterator<E> arrayListIterator(E[] array, int start, int end) Gets a list iterator over part of an object array.static <E> ResettableListIterator<E> arrayListIterator(Object array) Gets a list iterator over an object or primitive array.static <E> ResettableListIterator<E> arrayListIterator(Object array, int start) Gets a list iterator over the end part of an object or primitive array.static <E> ResettableListIterator<E> arrayListIterator(Object array, int start, int end) Gets a list iterator over part of an object or primitive array.static <E> Enumeration<E> asEnumeration(Iterator<? extends E> iterator) Gets an enumeration that wraps an iterator.static <E> Iterable<E> asIterable(Iterator<? extends E> iterator) Gets anIterablethat wraps an iterator.static <E> Iterator<E> asIterator(Enumeration<? extends E> enumeration) Gets an iterator that provides an iterator view of the given enumeration.static <E> Iterator<E> asIterator(Enumeration<? extends E> enumeration, Collection<? super E> removeCollection) Gets an iterator that provides an iterator view of the given enumeration that will remove elements from the specified collection.static <E> Iterable<E> asMultipleUseIterable(Iterator<? extends E> iterator) Gets an iterable that wraps an iterator.static <E> BoundedIterator<E> boundedIterator(Iterator<? extends E> iterator, long max) Decorates the specified iterator to return at most the given number of elements.static <E> BoundedIterator<E> boundedIterator(Iterator<? extends E> iterator, long offset, long max) Decorates the specified iterator to return at most the given number of elements, skipping all elements until the iterator reaches the position atoffset.static <E> Iterator<E> chainedIterator(Collection<? extends Iterator<? extends E>> iterators) Gets an iterator that iterates through a collections ofIterators one after another.static <E> Iterator<E> chainedIterator(Iterator<? extends E>... iterators) Gets an iterator that iterates through an array ofIterators one after another.static <E> Iterator<E> chainedIterator(Iterator<? extends E> iterator1, Iterator<? extends E> iterator2) Gets an iterator that iterates through twoIterators one after another.static <E> Iterator<E> chainedIterator(Iterator<? extends Iterator<? extends E>> iterators) Gets an iterator that iterates through anIteratorof Iterators one after another.static <E> Iterator<E> collatedIterator(Comparator<? super E> comparator, Collection<Iterator<? extends E>> iterators) Gets an iterator that provides an ordered iteration over the elements contained in a collection ofIterators.static <E> Iterator<E> collatedIterator(Comparator<? super E> comparator, Iterator<? extends E>... iterators) Gets an iterator that provides an ordered iteration over the elements contained in an array ofIterators.static <E> Iterator<E> collatedIterator(Comparator<? super E> comparator, Iterator<? extends E> iterator1, Iterator<? extends E> iterator2) Gets an iterator that provides an ordered iteration over the elements contained in a collection of orderedIterators.static <E> booleanChecks if the object is contained in the given iterator.static <E> ResettableIterator<E> Gets an empty iterator.static <E> ResettableListIterator<E> Gets an empty list iterator.static <K,V> MapIterator <K, V> Gets an empty map iterator.static <E> OrderedIterator<E> Gets an empty ordered iterator.static <K,V> OrderedMapIterator <K, V> Gets an empty ordered map iterator.static <E> Iterator<E> filteredIterator(Iterator<? extends E> iterator, Predicate<? super E> predicate) Gets an iterator that filters another iterator.static <E> ListIterator<E> filteredListIterator(ListIterator<? extends E> listIterator, Predicate<? super E> predicate) Gets a list iterator that filters another list iterator.static <E> EFinds the first element in the given iterator which matches the given predicate.static <E> EShortcut forget(iterator, 0).static <E> voidApplies the closure to each element of the provided iterator.static <E> EforEachButLast(Iterator<E> iterator, Closure<? super E> closure) Executes the given closure on each but the last element in the iterator.static <E> EGets theindex-th value inIterator, throwingIndexOutOfBoundsExceptionif there is no such element.static Iterator<?> getIterator(Object obj) Gets a suitable Iterator for the given object.static <E> intReturns the index of the first element in the specified iterator that matches the given predicate.static booleanChecks if the given iterator is empty.static <E> ResettableIterator<E> loopingIterator(Collection<? extends E> collection) Gets an iterator that loops continuously over the supplied collection.static <E> ResettableListIterator<E> loopingListIterator(List<E> list) Gets an iterator that loops continuously over the supplied list.static <E> booleanmatchesAll(Iterator<E> iterator, Predicate<? super E> predicate) Answers true if a predicate is true for every element of an iterator.static <E> booleanmatchesAny(Iterator<E> iterator, Predicate<? super E> predicate) Answers true if a predicate is true for any element of the iterator.static NodeListIteratornodeListIterator(Node node) Gets anIteratorthat wraps the specified node's childNodes.static NodeListIteratornodeListIterator(NodeList nodeList) static <E> Iterator<E> objectGraphIterator(E root, Transformer<? super E, ? extends E> transformer) Gets an iterator that operates over an object graph.static <E> Iterator<E> peekingIterator(Iterator<? extends E> iterator) Gets an iterator that supports one-element lookahead.static <E> Iterator<E> pushbackIterator(Iterator<? extends E> iterator) Gets an iterator that supports pushback of elements.static <E> ResettableIterator<E> singletonIterator(E object) Gets a singleton iterator.static <E> ListIterator<E> singletonListIterator(E object) Gets a singleton list iterator.static intReturns the number of elements contained in the given iterator.static <E> SkippingIterator<E> skippingIterator(Iterator<E> iterator, long offset) Decorates the specified iterator to skip the first N elements.static <E> Stream<E> Creates a stream on the given Iterable.static <E> Stream<E> Creates a stream on the given Iterator.static Object[]Gets an array based on an iterator.static <E> E[]Gets an array based on an iterator.static <E> List<E> Gets a list based on an iterator.static <E> List<E> Gets a list based on an iterator.static <E> ListIterator<E> toListIterator(Iterator<? extends E> iterator) Gets a list iterator based on a simple iterator.static <E> Set<E> Gets a set based on an iterator.static <E> Set<E> Gets a set based on an iterator.static <E> StringReturns a string representation of the elements of the specified iterator.static <E> StringtoString(Iterator<E> iterator, Transformer<? super E, String> transformer) Returns a string representation of the elements of the specified iterator.static <E> StringtoString(Iterator<E> iterator, Transformer<? super E, String> transformer, String delimiter, String prefix, String suffix) Returns a string representation of the elements of the specified iterator.static <I,O> Iterator <O> transformedIterator(Iterator<? extends I> iterator, Transformer<? super I, ? extends O> transformer) Gets an iterator that transforms the elements of another iterator.static <E> Iterator<E> unmodifiableIterator(Iterator<E> iterator) Gets an immutable version of anIterator.static <E> ListIterator<E> unmodifiableListIterator(ListIterator<E> listIterator) Gets an immutable version of aListIterator.static <K,V> MapIterator <K, V> unmodifiableMapIterator(MapIterator<K, V> mapIterator) Gets an immutable version of aMapIterator.static <E> ZippingIterator<E> zippingIterator(Iterator<? extends E>... iterators) Returns an iterator that interleaves elements from the decorated iterators.static <E> ZippingIterator<E> zippingIterator(Iterator<? extends E> a, Iterator<? extends E> b) Returns an iterator that interleaves elements from the decorated iterators.static <E> ZippingIterator<E> zippingIterator(Iterator<? extends E> a, Iterator<? extends E> b, Iterator<? extends E> c) Returns an iterator that interleaves elements from the decorated iterators.
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Field Details- 
EMPTY_ITERATORAn iterator over no elements.
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EMPTY_LIST_ITERATORA list iterator over no elements.
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EMPTY_ORDERED_ITERATORAn ordered iterator over no elements.
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EMPTY_MAP_ITERATORA map iterator over no elements.
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EMPTY_ORDERED_MAP_ITERATORAn ordered map iterator over no elements.
 
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Method Details- 
arrayIteratorGets an iterator over an object array.- Type Parameters:
- E- the element type
- Parameters:
- array- the array over which to iterate
- Returns:
- an iterator over the array
- Throws:
- NullPointerException- if array is null
 
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arrayIteratorGets an iterator over the end part of an object array.- Type Parameters:
- E- the element type
- Parameters:
- array- the array over which to iterate
- start- the index to start iterating at
- Returns:
- an iterator over part of the array
- Throws:
- IndexOutOfBoundsException- if start is less than zero or greater than the length of the array
- NullPointerException- if array is null
 
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arrayIteratorGets an iterator over part of an object array.- Type Parameters:
- E- the element type
- Parameters:
- array- the array over which to iterate
- start- the index to start iterating at
- end- the index to finish iterating at
- Returns:
- an iterator over part of the array
- Throws:
- IndexOutOfBoundsException- if array bounds are invalid
- IllegalArgumentException- if end is before start
- NullPointerException- if array is null
 
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arrayIteratorGets an iterator over an object or primitive array.This method will handle primitive arrays as well as object arrays. The primitives will be wrapped in the appropriate wrapper class. - Type Parameters:
- E- the element type
- Parameters:
- array- the array over which to iterate
- Returns:
- an iterator over the array
- Throws:
- IllegalArgumentException- if the array is not an array
- NullPointerException- if array is null
 
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arrayIteratorGets an iterator over the end part of an object or primitive array.This method will handle primitive arrays as well as object arrays. The primitives will be wrapped in the appropriate wrapper class. - Type Parameters:
- E- the element type
- Parameters:
- array- the array over which to iterate
- start- the index to start iterating at
- Returns:
- an iterator over part of the array
- Throws:
- IllegalArgumentException- if the array is not an array
- IndexOutOfBoundsException- if start is less than zero or greater than the length of the array
- NullPointerException- if array is null
 
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arrayIteratorGets an iterator over part of an object or primitive array.This method will handle primitive arrays as well as object arrays. The primitives will be wrapped in the appropriate wrapper class. - Type Parameters:
- E- the element type
- Parameters:
- array- the array over which to iterate
- start- the index to start iterating at
- end- the index to finish iterating at
- Returns:
- an iterator over part of the array
- Throws:
- IllegalArgumentException- if the array is not an array or end is before start
- IndexOutOfBoundsException- if array bounds are invalid
- NullPointerException- if array is null
 
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arrayListIteratorGets a list iterator over an object array.- Type Parameters:
- E- the element type
- Parameters:
- array- the array over which to iterate
- Returns:
- a list iterator over the array
- Throws:
- NullPointerException- if array is null
 
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arrayListIteratorGets a list iterator over the end part of an object array.- Type Parameters:
- E- the element type
- Parameters:
- array- the array over which to iterate
- start- the index to start iterating at
- Returns:
- a list iterator over part of the array
- Throws:
- IndexOutOfBoundsException- if start is less than zero
- NullPointerException- if array is null
 
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arrayListIteratorGets a list iterator over part of an object array.- Type Parameters:
- E- the element type
- Parameters:
- array- the array over which to iterate
- start- the index to start iterating at
- end- the index to finish iterating at
- Returns:
- a list iterator over part of the array
- Throws:
- IndexOutOfBoundsException- if array bounds are invalid
- IllegalArgumentException- if end is before start
- NullPointerException- if array is null
 
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arrayListIteratorGets a list iterator over an object or primitive array.This method will handle primitive arrays as well as object arrays. The primitives will be wrapped in the appropriate wrapper class. - Type Parameters:
- E- the element type
- Parameters:
- array- the array over which to iterate
- Returns:
- a list iterator over the array
- Throws:
- IllegalArgumentException- if the array is not an array
- NullPointerException- if array is null
 
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arrayListIteratorGets a list iterator over the end part of an object or primitive array.This method will handle primitive arrays as well as object arrays. The primitives will be wrapped in the appropriate wrapper class. - Type Parameters:
- E- the element type
- Parameters:
- array- the array over which to iterate
- start- the index to start iterating at
- Returns:
- a list iterator over part of the array
- Throws:
- IllegalArgumentException- if the array is not an array
- IndexOutOfBoundsException- if start is less than zero
- NullPointerException- if array is null
 
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arrayListIteratorGets a list iterator over part of an object or primitive array.This method will handle primitive arrays as well as object arrays. The primitives will be wrapped in the appropriate wrapper class. - Type Parameters:
- E- the element type
- Parameters:
- array- the array over which to iterate
- start- the index to start iterating at
- end- the index to finish iterating at
- Returns:
- a list iterator over part of the array
- Throws:
- IllegalArgumentException- if the array is not an array or end is before start
- IndexOutOfBoundsException- if array bounds are invalid
- NullPointerException- if array is null
 
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asEnumerationGets an enumeration that wraps an iterator.- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to use, may not be null
- Returns:
- a new enumeration
- Throws:
- NullPointerException- if iterator is null
 
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asIterable- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to use, may not be null
- Returns:
- a new, single use Iterable
- Throws:
- NullPointerException- if iterator is null
 
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asIteratorGets an iterator that provides an iterator view of the given enumeration.- Type Parameters:
- E- the element type
- Parameters:
- enumeration- the enumeration to use, may not be null
- Returns:
- a new iterator
- Throws:
- NullPointerException- if enumeration is null
 
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asIteratorpublic static <E> Iterator<E> asIterator(Enumeration<? extends E> enumeration, Collection<? super E> removeCollection) Gets an iterator that provides an iterator view of the given enumeration that will remove elements from the specified collection.- Type Parameters:
- E- the element type
- Parameters:
- enumeration- the enumeration to use, may not be null
- removeCollection- the collection to remove elements from, may not be null
- Returns:
- a new iterator
- Throws:
- NullPointerException- if enumeration or removeCollection is null
 
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asMultipleUseIterableGets an iterable that wraps an iterator. The returned iterable can be used for multiple iterations.- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to use, may not be null
- Returns:
- a new, multiple use iterable
- Throws:
- NullPointerException- if iterator is null
 
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boundedIteratorDecorates the specified iterator to return at most the given number of elements.- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to decorate
- max- the maximum number of elements returned by this iterator
- Returns:
- a new bounded iterator
- Throws:
- NullPointerException- if the iterator is null
- IllegalArgumentException- if max is negative
- Since:
- 4.1
 
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boundedIteratorpublic static <E> BoundedIterator<E> boundedIterator(Iterator<? extends E> iterator, long offset, long max) Decorates the specified iterator to return at most the given number of elements, skipping all elements until the iterator reaches the position atoffset.The iterator is immediately advanced until it reaches the position at offset, incurring O(n) time.- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to decorate
- offset- the index of the first element of the decorated iterator to return
- max- the maximum number of elements returned by this iterator
- Returns:
- a new bounded iterator
- Throws:
- NullPointerException- if the iterator is null
- IllegalArgumentException- if either offset or max is negative
- Since:
- 4.1
 
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chainedIteratorpublic static <E> Iterator<E> chainedIterator(Collection<? extends Iterator<? extends E>> iterators) Gets an iterator that iterates through a collections ofIterators one after another.- Type Parameters:
- E- the element type
- Parameters:
- iterators- the iterators to use, not null or empty or contain nulls
- Returns:
- a combination iterator over the iterators
- Throws:
- NullPointerException- if iterators collection is null or contains a null
- ClassCastException- if the iterators collection contains the wrong object type
 
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chainedIteratorGets an iterator that iterates through an array ofIterators one after another.- Type Parameters:
- E- the element type
- Parameters:
- iterators- the iterators to use, not null or empty or contain nulls
- Returns:
- a combination iterator over the iterators
- Throws:
- NullPointerException- if iterators array is null or contains a null
 
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chainedIteratorpublic static <E> Iterator<E> chainedIterator(Iterator<? extends E> iterator1, Iterator<? extends E> iterator2) Gets an iterator that iterates through twoIterators one after another.- Type Parameters:
- E- the element type
- Parameters:
- iterator1- the first iterator to use, not null
- iterator2- the second iterator to use, not null
- Returns:
- a combination iterator over the iterators
- Throws:
- NullPointerException- if either iterator is null
 
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chainedIteratorGets an iterator that iterates through anIteratorof Iterators one after another.- Type Parameters:
- E- the element type
- Parameters:
- iterators- the iterators to use, not null or empty or contain nulls
- Returns:
- a combination iterator over the iterators
- Throws:
- NullPointerException- if iterators collection is null or contains a null
- ClassCastException- if the iterators collection contains the wrong object type
- Since:
- 4.5.0-M3
 
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collatedIteratorpublic static <E> Iterator<E> collatedIterator(Comparator<? super E> comparator, Collection<Iterator<? extends E>> iterators) Gets an iterator that provides an ordered iteration over the elements contained in a collection ofIterators.Given two ordered IteratorsAandB, theIterator.next()method will return the lesser ofA.next()andB.next()and so on.The comparator is optional. If null is specified then natural order is used. - Type Parameters:
- E- the element type
- Parameters:
- comparator- the comparator to use, may be null for natural order
- iterators- the iterators to use, not null or empty or contain nulls
- Returns:
- a combination iterator over the iterators
- Throws:
- NullPointerException- if iterators collection is null or contains a null
- ClassCastException- if the iterators collection contains the wrong object type
 
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collatedIteratorpublic static <E> Iterator<E> collatedIterator(Comparator<? super E> comparator, Iterator<? extends E>... iterators) Gets an iterator that provides an ordered iteration over the elements contained in an array ofIterators.Given two ordered IteratorsAandB, theIterator.next()method will return the lesser ofA.next()andB.next()and so on.The comparator is optional. If null is specified then natural order is used. - Type Parameters:
- E- the element type
- Parameters:
- comparator- the comparator to use, may be null for natural order
- iterators- the iterators to use, not null or empty or contain nulls
- Returns:
- a combination iterator over the iterators
- Throws:
- NullPointerException- if iterators array is null or contains a null value
 
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collatedIteratorpublic static <E> Iterator<E> collatedIterator(Comparator<? super E> comparator, Iterator<? extends E> iterator1, Iterator<? extends E> iterator2) Gets an iterator that provides an ordered iteration over the elements contained in a collection of orderedIterators.Given two ordered IteratorsAandB, theIterator.next()method will return the lesser ofA.next()andB.next().The comparator is optional. If null is specified then natural order is used. - Type Parameters:
- E- the element type
- Parameters:
- comparator- the comparator to use, may be null for natural order
- iterator1- the first iterators to use, not null
- iterator2- the first iterators to use, not null
- Returns:
- a combination iterator over the iterators
- Throws:
- NullPointerException- if either iterator is null
 
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containsChecks if the object is contained in the given iterator.A nullor empty iterator returns false.- Type Parameters:
- E- the type of object the- Iteratorcontains
- Parameters:
- iterator- the iterator to check, may be null
- object- the object to check
- Returns:
- true if the object is contained in the iterator, false otherwise
- Since:
- 4.1
 
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emptyIteratorGets an empty iterator.This iterator is a valid iterator object that will iterate over nothing. - Type Parameters:
- E- the element type
- Returns:
- an iterator over nothing
 
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emptyListIteratorGets an empty list iterator.This iterator is a valid list iterator object that will iterate over nothing. - Type Parameters:
- E- the element type
- Returns:
- a list iterator over nothing
 
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emptyMapIteratorGets an empty map iterator.This iterator is a valid map iterator object that will iterate over nothing. - Type Parameters:
- K- the key type
- V- the value type
- Returns:
- a map iterator over nothing
 
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emptyOrderedIteratorGets an empty ordered iterator.This iterator is a valid iterator object that will iterate over nothing. - Type Parameters:
- E- the element type
- Returns:
- an ordered iterator over nothing
 
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emptyOrderedMapIteratorGets an empty ordered map iterator.This iterator is a valid map iterator object that will iterate over nothing. - Type Parameters:
- K- the key type
- V- the value type
- Returns:
- a map iterator over nothing
 
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filteredIteratorpublic static <E> Iterator<E> filteredIterator(Iterator<? extends E> iterator, Predicate<? super E> predicate) Gets an iterator that filters another iterator.The returned iterator will only return objects that match the specified filtering predicate. - Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to use, not null
- predicate- the predicate to use as a filter, not null
- Returns:
- a new filtered iterator
- Throws:
- NullPointerException- if either parameter is null
 
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filteredListIteratorpublic static <E> ListIterator<E> filteredListIterator(ListIterator<? extends E> listIterator, Predicate<? super E> predicate) Gets a list iterator that filters another list iterator.The returned iterator will only return objects that match the specified filtering predicate. - Type Parameters:
- E- the element type
- Parameters:
- listIterator- the list iterator to use, not null
- predicate- the predicate to use as a filter, not null
- Returns:
- a new filtered iterator
- Throws:
- NullPointerException- if either parameter is null
 
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findFinds the first element in the given iterator which matches the given predicate.A nullor empty iterator returns null.- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to search, may be null
- predicate- the predicate to use, must not be null
- Returns:
- the first element of the iterator which matches the predicate or null if none could be found
- Throws:
- NullPointerException- if predicate is null
- Since:
- 4.1
 
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firstShortcut forget(iterator, 0).Returns the firstvalue inIterator, throwingIndexOutOfBoundsExceptionif there is no such element.The Iterator is advanced to 0(or to the end, if0exceeds the number of entries) as a side effect of this method.- Type Parameters:
- E- the type of object in the- Iterator
- Parameters:
- iterator- the iterator to get a value from
- Returns:
- the first object
- Throws:
- IndexOutOfBoundsException- if the request is invalid
- Since:
- 4.2
 
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forEachApplies the closure to each element of the provided iterator.- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to use, may be null
- closure- the closure to apply to each element, may not be null
- Throws:
- NullPointerException- if closure is null
- Since:
- 4.1
 
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forEachButLastExecutes the given closure on each but the last element in the iterator.If the input iterator is null no change is made. - Type Parameters:
- E- the type of object the- Iteratorcontains
- Parameters:
- iterator- the iterator to get the input from, may be null
- closure- the closure to perform, may not be null
- Returns:
- the last element in the iterator, or null if iterator is null or empty
- Throws:
- NullPointerException- if closure is null
- Since:
- 4.1
 
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getGets theindex-th value inIterator, throwingIndexOutOfBoundsExceptionif there is no such element.The Iterator is advanced to index(or to the end, ifindexexceeds the number of entries) as a side effect of this method.- Type Parameters:
- E- the type of object in the- Iterator.
- Parameters:
- iterator- the iterator to get a value from.
- index- the index to get, 0-based.
- Returns:
- the object at the specified index.
- Throws:
- IndexOutOfBoundsException- if the index is invalid.
- Since:
- 4.1
 
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getIteratorGets a suitable Iterator for the given object.This method can handle objects as follows - null - empty iterator
- Iterator - returned directly
- Enumeration - wrapped
- Collection - iterator from collection returned
- Map - values iterator returned
- Dictionary - values (elements) enumeration returned as iterator
- array - iterator over array returned
- object with iterator() public method accessed by reflection
- object - singleton iterator
- NodeList - iterator over the list
- Node - iterator over the child nodes
 - Parameters:
- obj- the object to convert to an iterator
- Returns:
- a suitable iterator, never null
 
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indexOfReturns the index of the first element in the specified iterator that matches the given predicate.A nullor empty iterator returns -1.- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to search, may be null
- predicate- the predicate to use, may not be null
- Returns:
- the index of the first element which matches the predicate or -1 if none matches
- Throws:
- NullPointerException- if predicate is null
- Since:
- 4.1
 
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isEmpty
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loopingIteratorGets an iterator that loops continuously over the supplied collection.The iterator will only stop looping if the remove method is called enough times to empty the collection, or if the collection is empty to start with. - Type Parameters:
- E- the element type
- Parameters:
- collection- the collection to iterate over, not null
- Returns:
- a new looping iterator
- Throws:
- NullPointerException- if the collection is null
 
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loopingListIteratorGets an iterator that loops continuously over the supplied list.The iterator will only stop looping if the remove method is called enough times to empty the list, or if the list is empty to start with. - Type Parameters:
- E- the element type
- Parameters:
- list- the list to iterate over, not null
- Returns:
- a new looping iterator
- Throws:
- NullPointerException- if the list is null
- Since:
- 3.2
 
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matchesAllAnswers true if a predicate is true for every element of an iterator.A nullor empty iterator returns true.- Type Parameters:
- E- the type of object the- Iteratorcontains
- Parameters:
- iterator- the- Iteratorto use, may be null
- predicate- the predicate to use, may not be null
- Returns:
- true if every element of the collection matches the predicate or if the collection is empty, false otherwise
- Throws:
- NullPointerException- if predicate is null
- Since:
- 4.1
 
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matchesAnyAnswers true if a predicate is true for any element of the iterator.A nullor empty iterator returns false.- Type Parameters:
- E- the type of object the- Iteratorcontains
- Parameters:
- iterator- the- Iteratorto use, may be null
- predicate- the predicate to use, may not be null
- Returns:
- true if any element of the collection matches the predicate, false otherwise
- Throws:
- NullPointerException- if predicate is null
- Since:
- 4.1
 
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nodeListIteratorGets anIteratorthat wraps the specified node's childNodes. The returnedIteratorcan be used for a single iteration.Convenience method, allows easy iteration over NodeLists: Iterator<Node> iterator = IteratorUtils.nodeListIterator(node); for (Node childNode : IteratorUtils.asIterable(iterator)) { ... }- Parameters:
- node- the node to use, may not be null
- Returns:
- a new, single use Iterator
- Throws:
- NullPointerException- if node is null
- Since:
- 4.0
 
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nodeListIteratorGets anIteratorthat wraps the specifiedNodeList. The returnedIteratorcan be used for a single iteration.- Parameters:
- nodeList- the node list to use, may not be null
- Returns:
- a new, single use Iterator
- Throws:
- NullPointerException- if nodeList is null
- Since:
- 4.0
 
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objectGraphIteratorpublic static <E> Iterator<E> objectGraphIterator(E root, Transformer<? super E, ? extends E> transformer) Gets an iterator that operates over an object graph.This iterator can extract multiple objects from a complex tree-like object graph. The iteration starts from a single root object. It uses a Transformerto extract the iterators and elements. Its main benefit is that no intermediateListis created.For example, consider an object graph: |- Branch -- Leaf | \- Leaf |- Tree | /- Leaf | |- Branch -- Leaf Forest | \- Leaf | |- Branch -- Leaf | | \- Leaf |- Tree | /- Leaf |- Branch -- Leaf |- Branch -- LeafThe following Transformer, used in this class, will extract all the Leaf objects without creating a combined intermediate list:public Object transform(Object input) { if (input instanceof Forest) { return ((Forest) input).treeIterator(); } if (input instanceof Tree) { return ((Tree) input).branchIterator(); } if (input instanceof Branch) { return ((Branch) input).leafIterator(); } if (input instanceof Leaf) { return input; } throw new ClassCastException(); }Internally, iteration starts from the root object. When next is called, the transformer is called to examine the object. The transformer will return either an iterator or an object. If the object is an Iterator, the next element from that iterator is obtained and the process repeats. If the element is an object it is returned. Under many circumstances, linking Iterators together in this manner is more efficient (and convenient) than using nested for loops to extract a list. - Type Parameters:
- E- the element type
- Parameters:
- root- the root object to start iterating from, null results in an empty iterator
- transformer- the transformer to use, see above, null uses no effect transformer
- Returns:
- a new object graph iterator
- Since:
- 3.1
 
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peekingIteratorGets an iterator that supports one-element lookahead.- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to decorate, not null
- Returns:
- a peeking iterator
- Throws:
- NullPointerException- if the iterator is null
- Since:
- 4.0
 
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pushbackIteratorGets an iterator that supports pushback of elements.- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to decorate, not null
- Returns:
- a pushback iterator
- Throws:
- NullPointerException- if the iterator is null
- Since:
- 4.0
 
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singletonIteratorGets a singleton iterator.This iterator is a valid iterator object that will iterate over the specified object. - Type Parameters:
- E- the element type
- Parameters:
- object- the single object over which to iterate
- Returns:
- a singleton iterator over the object
 
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singletonListIteratorGets a singleton list iterator.This iterator is a valid list iterator object that will iterate over the specified object. - Type Parameters:
- E- the element type
- Parameters:
- object- the single object over which to iterate
- Returns:
- a singleton list iterator over the object
 
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size
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skippingIteratorDecorates the specified iterator to skip the first N elements.- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to decorate
- offset- the first number of elements to skip
- Returns:
- a new skipping iterator
- Throws:
- NullPointerException- if the iterator is null
- IllegalArgumentException- if offset is negative
- Since:
- 4.1
 
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streamCreates a stream on the given Iterable.- Type Parameters:
- E- the type of elements in the Iterable.
- Parameters:
- iterable- the Iterable to stream or null.
- Returns:
- a new Stream or Stream.empty()if the Iterable is null.
- Since:
- 4.5.0-M3
 
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streamCreates a stream on the given Iterator.- Type Parameters:
- E- the type of elements in the Iterator.
- Parameters:
- iterator- the Iterator to stream or null.
- Returns:
- a new Stream or Stream.empty()if the Iterator is null.
- Since:
- 4.5.0-M3
 
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toArrayGets an array based on an iterator.As the wrapped Iterator is traversed, an ArrayList of its values is created. At the end, this is converted to an array. - Parameters:
- iterator- the iterator to use, not null
- Returns:
- an array of the iterator contents
- Throws:
- NullPointerException- if iterator parameter is null
 
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toArrayGets an array based on an iterator.As the wrapped Iterator is traversed, an ArrayList of its values is created. At the end, this is converted to an array. - Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to use, not null
- arrayClass- the class of array to create
- Returns:
- an array of the iterator contents
- Throws:
- NullPointerException- if iterator parameter or arrayClass is null
- ArrayStoreException- if the arrayClass is invalid
 
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toListGets a list based on an iterator.As the wrapped Iterator is traversed, an ArrayList of its values is created. At the end, the list is returned. - Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to use, not null
- Returns:
- a list of the iterator contents
- Throws:
- NullPointerException- if iterator parameter is null
 
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toListGets a list based on an iterator.As the wrapped Iterator is traversed, an ArrayList of its values is created. At the end, the list is returned. - Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to use, not null
- estimatedSize- the initial size of the ArrayList
- Returns:
- a list of the iterator contents
- Throws:
- NullPointerException- if iterator parameter is null
- IllegalArgumentException- if the size is less than 1
 
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toListIteratorGets a list iterator based on a simple iterator.As the wrapped Iterator is traversed, a LinkedList of its values is cached, permitting all required operations of ListIterator. - Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to use, may not be null
- Returns:
- a new iterator
- Throws:
- NullPointerException- if iterator parameter is null
 
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toSetGets a set based on an iterator.As the wrapped Iterator is traversed, a HashSet of its values is created. At the end, the set is returned. - Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to use, not null
- Returns:
- a set of the iterator contents
- Throws:
- NullPointerException- if iterator parameter is null
- Since:
- 4.5.0-M4
 
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toSetGets a set based on an iterator.As the wrapped Iterator is traversed, a HashSet of its values is created. At the end, the set is returned. - Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to use, not null
- estimatedSize- the initial size of the HashSet
- Returns:
- a list of the iterator contents
- Throws:
- NullPointerException- if iterator parameter is null
- IllegalArgumentException- if the size is less than 1
- Since:
- 4.5.0-M4
 
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toStringReturns a string representation of the elements of the specified iterator.The string representation consists of a list of the iterator's elements, enclosed in square brackets ( "[]"). Adjacent elements are separated by the characters", "(a comma followed by a space). Elements are converted to strings as byString.valueOf(Object).- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to convert to a string, may be null
- Returns:
- a string representation of iterator
- Since:
- 4.1
 
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toStringReturns a string representation of the elements of the specified iterator.The string representation consists of a list of the iterable's elements, enclosed in square brackets ( "[]"). Adjacent elements are separated by the characters", "(a comma followed by a space). Elements are converted to strings as by using the providedtransformer.- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to convert to a string, may be null
- transformer- the transformer used to get a string representation of an element
- Returns:
- a string representation of iterator
- Throws:
- NullPointerException- if- transformeris null
- Since:
- 4.1
 
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toStringpublic static <E> String toString(Iterator<E> iterator, Transformer<? super E, String> transformer, String delimiter, String prefix, String suffix) Returns a string representation of the elements of the specified iterator.The string representation consists of a list of the iterator's elements, enclosed by the provided prefixandsuffix. Adjacent elements are separated by the provideddelimiter. Elements are converted to strings as by using the providedtransformer.- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to convert to a string, may be null
- transformer- the transformer used to get a string representation of an element
- delimiter- the string to delimit elements
- prefix- the prefix, prepended to the string representation
- suffix- the suffix, appended to the string representation
- Returns:
- a string representation of iterator
- Throws:
- NullPointerException- if either transformer, delimiter, prefix or suffix is null
- Since:
- 4.1
 
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transformedIteratorpublic static <I,O> Iterator<O> transformedIterator(Iterator<? extends I> iterator, Transformer<? super I, ? extends O> transformer) Gets an iterator that transforms the elements of another iterator.The transformation occurs during the next() method and the underlying iterator is unaffected by the transformation. - Type Parameters:
- I- the input type
- O- the output type
- Parameters:
- iterator- the iterator to use, not null
- transformer- the transform to use, not null
- Returns:
- a new transforming iterator
- Throws:
- NullPointerException- if either parameter is null
 
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unmodifiableIteratorGets an immutable version of anIterator. The returned object will always throw anUnsupportedOperationExceptionfor theIterator.remove()method.- Type Parameters:
- E- the element type
- Parameters:
- iterator- the iterator to make immutable
- Returns:
- an immutable version of the iterator
 
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unmodifiableListIteratorGets an immutable version of aListIterator. The returned object will always throw anUnsupportedOperationExceptionfor theIterator.remove(),ListIterator.add(E)andListIterator.set(E)methods.- Type Parameters:
- E- the element type
- Parameters:
- listIterator- the iterator to make immutable
- Returns:
- an immutable version of the iterator
 
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unmodifiableMapIteratorGets an immutable version of aMapIterator. The returned object will always throw anUnsupportedOperationExceptionfor theIterator.remove(),MapIterator.setValue(Object)methods.- Type Parameters:
- K- the key type
- V- the value type
- Parameters:
- mapIterator- the iterator to make immutable
- Returns:
- an immutable version of the iterator
 
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zippingIteratorReturns an iterator that interleaves elements from the decorated iterators.- Type Parameters:
- E- the element type
- Parameters:
- iterators- the array of iterators to interleave
- Returns:
- an iterator, interleaving the decorated iterators
- Throws:
- NullPointerException- if any iterator is null
- Since:
- 4.1
 
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zippingIteratorpublic static <E> ZippingIterator<E> zippingIterator(Iterator<? extends E> a, Iterator<? extends E> b) Returns an iterator that interleaves elements from the decorated iterators.- Type Parameters:
- E- the element type
- Parameters:
- a- the first iterator to interleave
- b- the second iterator to interleave
- Returns:
- an iterator, interleaving the decorated iterators
- Throws:
- NullPointerException- if any iterator is null
- Since:
- 4.1
 
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zippingIteratorpublic static <E> ZippingIterator<E> zippingIterator(Iterator<? extends E> a, Iterator<? extends E> b, Iterator<? extends E> c) Returns an iterator that interleaves elements from the decorated iterators.- Type Parameters:
- E- the element type
- Parameters:
- a- the first iterator to interleave
- b- the second iterator to interleave
- c- the third iterator to interleave
- Returns:
- an iterator, interleaving the decorated iterators
- Throws:
- NullPointerException- if any iterator is null
- Since:
- 4.1
 
 
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