java.lang.Object
- org.apache.commons.collections.IteratorUtils

```
@Deprecated(since="2021-04-30")
public class IteratorUtils
extends java.lang.Object
```
Deprecated.
Commons Collections 3 is in maintenance mode. Commons Collections 4 should be used instead.

Provides static utility methods and decorators for Iterator instances. The implementations are provided in the iterators subpackage.
WARNING: Due to human error certain binary incompatabilities were introduced between Commons Collections 2.1 and 3.0. The class remained source and test compatible, so if you can recompile all your classes and dependencies everything is OK. Those methods which are binary incompatible are marked as such, together with alternate solutions that are binary compatible against versions 2.1.1 and 3.1.

Since:

Commons Collections 2.1

Field Summary

Fields
Modifier and Type	Field	Description
`static ResettableIterator`	`EMPTY_ITERATOR`	Deprecated. An iterator over no elements.
`static ResettableListIterator`	`EMPTY_LIST_ITERATOR`	Deprecated. A list iterator over no elements.
`static MapIterator`	`EMPTY_MAP_ITERATOR`	Deprecated. A map iterator over no elements.
`static OrderedIterator`	`EMPTY_ORDERED_ITERATOR`	Deprecated. An ordered iterator over no elements.
`static OrderedMapIterator`	`EMPTY_ORDERED_MAP_ITERATOR`	Deprecated. An ordered map iterator over no elements.

Constructor Summary

Constructors
Constructor Description

IteratorUtils()
Deprecated.

IteratorUtils is not normally instantiated.

Method Summary

All Methods Static Methods Concrete Methods Deprecated Methods
Modifier and Type	Method	Description
`static ResettableIterator`	`arrayIterator(java.lang.Object array)`	Deprecated. Gets an iterator over an object or primitive array.
`static ResettableIterator`	`arrayIterator(java.lang.Object[] array)`	Deprecated. Gets an iterator over an object array.
`static ResettableIterator`	`arrayIterator(java.lang.Object[] array, int start)`	Deprecated. Gets an iterator over the end part of an object array.
`static ResettableIterator`	`arrayIterator(java.lang.Object[] array, int start, int end)`	Deprecated. Gets an iterator over part of an object array.
`static ResettableIterator`	`arrayIterator(java.lang.Object array, int start)`	Deprecated. Gets an iterator over the end part of an object or primitive array.
`static ResettableIterator`	`arrayIterator(java.lang.Object array, int start, int end)`	Deprecated. Gets an iterator over part of an object or primitive array.
`static ResettableListIterator`	`arrayListIterator(java.lang.Object array)`	Deprecated. Gets a list iterator over an object or primitive array.
`static ResettableListIterator`	`arrayListIterator(java.lang.Object[] array)`	Deprecated. Gets a list iterator over an object array.
`static ResettableListIterator`	`arrayListIterator(java.lang.Object[] array, int start)`	Deprecated. Gets a list iterator over the end part of an object array.
`static ResettableListIterator`	`arrayListIterator(java.lang.Object[] array, int start, int end)`	Deprecated. Gets a list iterator over part of an object array.
`static ResettableListIterator`	`arrayListIterator(java.lang.Object array, int start)`	Deprecated. Gets a list iterator over the end part of an object or primitive array.
`static ResettableListIterator`	`arrayListIterator(java.lang.Object array, int start, int end)`	Deprecated. Gets a list iterator over part of an object or primitive array.
`static java.util.Enumeration`	`asEnumeration(java.util.Iterator iterator)`	Deprecated. Gets an enumeration that wraps an iterator.
`static java.util.Iterator`	`asIterator(java.util.Enumeration enumeration)`	Deprecated. Gets an iterator that provides an iterator view of the given enumeration.
`static java.util.Iterator`	`asIterator(java.util.Enumeration enumeration, java.util.Collection removeCollection)`	Deprecated. Gets an iterator that provides an iterator view of the given enumeration that will remove elements from the specified collection.
`static java.util.Iterator`	`chainedIterator(java.util.Collection iterators)`	Deprecated. Gets an iterator that iterates through a collections of `Iterator`s one after another.
`static java.util.Iterator`	`chainedIterator(java.util.Iterator[] iterators)`	Deprecated. Gets an iterator that iterates through an array of `Iterator`s one after another.
`static java.util.Iterator`	`chainedIterator(java.util.Iterator iterator1, java.util.Iterator iterator2)`	Deprecated. Gets an iterator that iterates through two `Iterator`s one after another.
`static java.util.Iterator`	`collatedIterator(java.util.Comparator comparator, java.util.Collection iterators)`	Deprecated. Gets an iterator that provides an ordered iteration over the elements contained in a collection of `Iterator`s.
`static java.util.Iterator`	`collatedIterator(java.util.Comparator comparator, java.util.Iterator[] iterators)`	Deprecated. Gets an iterator that provides an ordered iteration over the elements contained in an array of `Iterator`s.
`static java.util.Iterator`	`collatedIterator(java.util.Comparator comparator, java.util.Iterator iterator1, java.util.Iterator iterator2)`	Deprecated. Gets an iterator that provides an ordered iteration over the elements contained in a collection of ordered `Iterator`s.
`static ResettableIterator`	`emptyIterator()`	Deprecated. Gets an empty iterator.
`static ResettableListIterator`	`emptyListIterator()`	Deprecated. Gets an empty list iterator.
`static MapIterator`	`emptyMapIterator()`	Deprecated. Gets an empty map iterator.
`static OrderedIterator`	`emptyOrderedIterator()`	Deprecated. Gets an empty ordered iterator.
`static OrderedMapIterator`	`emptyOrderedMapIterator()`	Deprecated. Gets an empty ordered map iterator.
`static java.util.Iterator`	`filteredIterator(java.util.Iterator iterator, Predicate predicate)`	Deprecated. Gets an iterator that filters another iterator.
`static java.util.ListIterator`	`filteredListIterator(java.util.ListIterator listIterator, Predicate predicate)`	Deprecated. Gets a list iterator that filters another list iterator.
`static java.util.Iterator`	`getIterator(java.lang.Object obj)`	Deprecated. Gets a suitable Iterator for the given object.
`static ResettableIterator`	`loopingIterator(java.util.Collection coll)`	Deprecated. Gets an iterator that loops continuously over the supplied collection.
`static ResettableListIterator`	`loopingListIterator(java.util.List list)`	Deprecated. Gets an iterator that loops continuously over the supplied list.
`static java.util.Iterator`	`objectGraphIterator(java.lang.Object root, Transformer transformer)`	Deprecated. Gets an iterator that operates over an object graph.
`static ResettableIterator`	`singletonIterator(java.lang.Object object)`	Deprecated. Gets a singleton iterator.
`static java.util.ListIterator`	`singletonListIterator(java.lang.Object object)`	Deprecated. Gets a singleton list iterator.
`static java.lang.Object[]`	`toArray(java.util.Iterator iterator)`	Deprecated. Gets an array based on an iterator.
`static java.lang.Object[]`	`toArray(java.util.Iterator iterator, java.lang.Class arrayClass)`	Deprecated. Gets an array based on an iterator.
`static java.util.List`	`toList(java.util.Iterator iterator)`	Deprecated. Gets a list based on an iterator.
`static java.util.List`	`toList(java.util.Iterator iterator, int estimatedSize)`	Deprecated. Gets a list based on an iterator.
`static java.util.ListIterator`	`toListIterator(java.util.Iterator iterator)`	Deprecated. Gets a list iterator based on a simple iterator.
`static java.util.Iterator`	`transformedIterator(java.util.Iterator iterator, Transformer transform)`	Deprecated. Gets an iterator that transforms the elements of another iterator.
`static java.util.Iterator`	`unmodifiableIterator(java.util.Iterator iterator)`	Deprecated. Gets an immutable version of an `Iterator`.
`static java.util.ListIterator`	`unmodifiableListIterator(java.util.ListIterator listIterator)`	Deprecated. Gets an immutable version of a `ListIterator`.
`static MapIterator`	`unmodifiableMapIterator(MapIterator mapIterator)`	Deprecated. Gets an immutable version of a `MapIterator`.

Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - EMPTY_ITERATOR
```
public static final ResettableIterator EMPTY_ITERATOR
```
    Deprecated.
    
    An iterator over no elements.
    WARNING: This constant is binary incompatible with Commons Collections 2.1 and 2.1.1. Use EmptyIterator.INSTANCE for compatability with Commons Collections 2.1.1.
  - EMPTY_LIST_ITERATOR
```
public static final ResettableListIterator EMPTY_LIST_ITERATOR
```
    Deprecated.
    
    A list iterator over no elements.
    WARNING: This constant is binary incompatible with Commons Collections 2.1 and 2.1.1. Use EmptyListIterator.INSTANCE for compatability with Commons Collections 2.1.1.
  - EMPTY_ORDERED_ITERATOR
```
public static final OrderedIterator EMPTY_ORDERED_ITERATOR
```
    Deprecated.
    
    An ordered iterator over no elements.
  - EMPTY_MAP_ITERATOR
```
public static final MapIterator EMPTY_MAP_ITERATOR
```
    Deprecated.
    
    A map iterator over no elements.
  - EMPTY_ORDERED_MAP_ITERATOR
```
public static final OrderedMapIterator EMPTY_ORDERED_MAP_ITERATOR
```
    Deprecated.
    
    An ordered map iterator over no elements.
- Constructor Detail
  - IteratorUtils
```
public IteratorUtils()
```
    Deprecated.
    
    IteratorUtils is not normally instantiated.
- Method Detail
  - emptyIterator
```
public static ResettableIterator emptyIterator()
```
    Deprecated.
    
    Gets an empty iterator.
    This iterator is a valid iterator object that will iterate over nothing.
    WARNING: This method is binary incompatible with Commons Collections 2.1 and 2.1.1. Use EmptyIterator.INSTANCE for compatability with Commons Collections 2.1.1.
    
    Returns:
    
    an iterator over nothing
  - emptyListIterator
```
public static ResettableListIterator emptyListIterator()
```
    Deprecated.
    
    Gets an empty list iterator.
    This iterator is a valid list iterator object that will iterate over nothing.
    WARNING: This method is binary incompatible with Commons Collections 2.1 and 2.1.1. Use EmptyListIterator.INSTANCE for compatability with Commons Collections 2.1.1.
    
    Returns:
    
    a list iterator over nothing
  - emptyOrderedIterator
```
public static OrderedIterator emptyOrderedIterator()
```
    Deprecated.
    
    Gets an empty ordered iterator.
    This iterator is a valid iterator object that will iterate over nothing.
    
    Returns:
    
    an ordered iterator over nothing
  - emptyMapIterator
```
public static MapIterator emptyMapIterator()
```
    Deprecated.
    
    Gets an empty map iterator.
    This iterator is a valid map iterator object that will iterate over nothing.
    
    Returns:
    
    a map iterator over nothing
  - emptyOrderedMapIterator
```
public static OrderedMapIterator emptyOrderedMapIterator()
```
    Deprecated.
    
    Gets an empty ordered map iterator.
    This iterator is a valid map iterator object that will iterate over nothing.
    
    Returns:
    
    a map iterator over nothing
  - singletonIterator
```
public static ResettableIterator singletonIterator(java.lang.Object object)
```
    Deprecated.
    
    Gets a singleton iterator.
    This iterator is a valid iterator object that will iterate over the specified object.
    WARNING: This method is binary incompatible with Commons Collections 2.1 and 2.1.1. Use new SingletonIterator(object) for compatability.
    
    Parameters:
    
    object - the single object over which to iterate
    
    Returns:
    
    a singleton iterator over the object
  - singletonListIterator
```
public static java.util.ListIterator singletonListIterator(java.lang.Object object)
```
    Deprecated.
    
    Gets a singleton list iterator.
    This iterator is a valid list iterator object that will iterate over the specified object.
    
    Parameters:
    
    object - the single object over which to iterate
    
    Returns:
    
    a singleton list iterator over the object
  - arrayIterator
```
public static ResettableIterator arrayIterator(java.lang.Object[] array)
```
    Deprecated.
    
    Gets an iterator over an object array.
    WARNING: This method is binary incompatible with Commons Collections 2.1 and 2.1.1. Use new ArrayIterator(array) for compatability.
    
    Parameters:
    
    array - the array over which to iterate
    
    Returns:
    
    an iterator over the array
    
    Throws:
    
    java.lang.NullPointerException - if array is null
  - arrayIterator
```
public static ResettableIterator arrayIterator(java.lang.Object array)
```
    Deprecated.
    
    Gets 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.
    
    Parameters:
    
    array - the array over which to iterate
    
    Returns:
    
    an iterator over the array
    
    Throws:
    
    java.lang.IllegalArgumentException - if the array is not an array
    
    java.lang.NullPointerException - if array is null
  - arrayIterator
```
public static ResettableIterator arrayIterator(java.lang.Object[] array,
                                               int start)
```
    Deprecated.
    
    Gets an iterator over the end part of an object array.
    WARNING: This method is binary incompatible with Commons Collections 2.1 and 2.1.1. Use new ArrayIterator(array,start) for compatability.
    
    Parameters:
    
    array - the array over which to iterate
    
    start - the index to start iterating at
    
    Returns:
    
    an iterator over part of the array
    
    Throws:
    
    java.lang.IndexOutOfBoundsException - if start is less than zero or greater than the length of the array
    
    java.lang.NullPointerException - if array is null
  - arrayIterator
```
public static ResettableIterator arrayIterator(java.lang.Object array,
                                               int start)
```
    Deprecated.
    
    Gets 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.
    
    Parameters:
    
    array - the array over which to iterate
    
    start - the index to start iterating at
    
    Returns:
    
    an iterator over part of the array
    
    Throws:
    
    java.lang.IllegalArgumentException - if the array is not an array
    
    java.lang.IndexOutOfBoundsException - if start is less than zero or greater than the length of the array
    
    java.lang.NullPointerException - if array is null
  - arrayIterator
```
public static ResettableIterator arrayIterator(java.lang.Object[] array,
                                               int start,
                                               int end)
```
    Deprecated.
    
    Gets an iterator over part of an object array.
    WARNING: This method is binary incompatible with Commons Collections 2.1 and 2.1.1. Use new ArrayIterator(array,start,end) for compatability.
    
    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:
    
    java.lang.IndexOutOfBoundsException - if array bounds are invalid
    
    java.lang.IllegalArgumentException - if end is before start
    
    java.lang.NullPointerException - if array is null
  - arrayIterator
```
public static ResettableIterator arrayIterator(java.lang.Object array,
                                               int start,
                                               int end)
```
    Deprecated.
    
    Gets 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.
    
    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:
    
    java.lang.IllegalArgumentException - if the array is not an array
    
    java.lang.IndexOutOfBoundsException - if array bounds are invalid
    
    java.lang.IllegalArgumentException - if end is before start
    
    java.lang.NullPointerException - if array is null
  - arrayListIterator
```
public static ResettableListIterator arrayListIterator(java.lang.Object[] array)
```
    Deprecated.
    
    Gets a list iterator over an object array.
    
    Parameters:
    
    array - the array over which to iterate
    
    Returns:
    
    a list iterator over the array
    
    Throws:
    
    java.lang.NullPointerException - if array is null
  - arrayListIterator
```
public static ResettableListIterator arrayListIterator(java.lang.Object array)
```
    Deprecated.
    
    Gets 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.
    
    Parameters:
    
    array - the array over which to iterate
    
    Returns:
    
    a list iterator over the array
    
    Throws:
    
    java.lang.IllegalArgumentException - if the array is not an array
    
    java.lang.NullPointerException - if array is null
  - arrayListIterator
```
public static ResettableListIterator arrayListIterator(java.lang.Object[] array,
                                                       int start)
```
    Deprecated.
    
    Gets a list iterator over the end part of an object array.
    
    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:
    
    java.lang.IndexOutOfBoundsException - if start is less than zero
    
    java.lang.NullPointerException - if array is null
  - arrayListIterator
```
public static ResettableListIterator arrayListIterator(java.lang.Object array,
                                                       int start)
```
    Deprecated.
    
    Gets 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.
    
    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:
    
    java.lang.IllegalArgumentException - if the array is not an array
    
    java.lang.IndexOutOfBoundsException - if start is less than zero
    
    java.lang.NullPointerException - if array is null
  - arrayListIterator
```
public static ResettableListIterator arrayListIterator(java.lang.Object[] array,
                                                       int start,
                                                       int end)
```
    Deprecated.
    
    Gets a list iterator over part of an object array.
    
    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:
    
    java.lang.IndexOutOfBoundsException - if array bounds are invalid
    
    java.lang.IllegalArgumentException - if end is before start
    
    java.lang.NullPointerException - if array is null
  - arrayListIterator
```
public static ResettableListIterator arrayListIterator(java.lang.Object array,
                                                       int start,
                                                       int end)
```
    Deprecated.
    
    Gets 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.
    
    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:
    
    java.lang.IllegalArgumentException - if the array is not an array
    
    java.lang.IndexOutOfBoundsException - if array bounds are invalid
    
    java.lang.IllegalArgumentException - if end is before start
    
    java.lang.NullPointerException - if array is null
  - unmodifiableIterator
```
public static java.util.Iterator unmodifiableIterator(java.util.Iterator iterator)
```
    Deprecated.
    
    Gets an immutable version of an Iterator. The returned object will always throw an UnsupportedOperationException for the Iterator.remove() method.
    
    Parameters:
    
    iterator - the iterator to make immutable
    
    Returns:
    
    an immutable version of the iterator
  - unmodifiableListIterator
```
public static java.util.ListIterator unmodifiableListIterator(java.util.ListIterator listIterator)
```
    Deprecated.
    
    Gets an immutable version of a ListIterator. The returned object will always throw an UnsupportedOperationException for the Iterator.remove(), ListIterator.add(E) and ListIterator.set(E) methods.
    
    Parameters:
    
    listIterator - the iterator to make immutable
    
    Returns:
    
    an immutable version of the iterator
  - unmodifiableMapIterator
```
public static MapIterator unmodifiableMapIterator(MapIterator mapIterator)
```
    Deprecated.
    
    Gets an immutable version of a MapIterator. The returned object will always throw an UnsupportedOperationException for the Iterator.remove(), MapIterator.setValue(Object) methods.
    
    Parameters:
    
    mapIterator - the iterator to make immutable
    
    Returns:
    
    an immutable version of the iterator
  - chainedIterator
```
public static java.util.Iterator chainedIterator(java.util.Iterator iterator1,
                                                 java.util.Iterator iterator2)
```
    Deprecated.
    
    Gets an iterator that iterates through two Iterators one after another.
    
    Parameters:
    
    iterator1 - the first iterators to use, not null
    
    iterator2 - the first iterators to use, not null
    
    Returns:
    
    a combination iterator over the iterators
    
    Throws:
    
    java.lang.NullPointerException - if either iterator is null
  - chainedIterator
```
public static java.util.Iterator chainedIterator(java.util.Iterator[] iterators)
```
    Deprecated.
    
    Gets an iterator that iterates through an array of Iterators one after another.
    
    Parameters:
    
    iterators - the iterators to use, not null or empty or contain nulls
    
    Returns:
    
    a combination iterator over the iterators
    
    Throws:
    
    java.lang.NullPointerException - if iterators array is null or contains a null
  - chainedIterator
```
public static java.util.Iterator chainedIterator(java.util.Collection iterators)
```
    Deprecated.
    
    Gets an iterator that iterates through a collections of Iterators one after another.
    
    Parameters:
    
    iterators - the iterators to use, not null or empty or contain nulls
    
    Returns:
    
    a combination iterator over the iterators
    
    Throws:
    
    java.lang.NullPointerException - if iterators collection is null or contains a null
    
    java.lang.ClassCastException - if the iterators collection contains the wrong object type
  - collatedIterator
```
public static java.util.Iterator collatedIterator(java.util.Comparator comparator,
                                                  java.util.Iterator iterator1,
                                                  java.util.Iterator iterator2)
```
    Deprecated.
    
    Gets an iterator that provides an ordered iteration over the elements contained in a collection of ordered Iterators.
    Given two ordered Iterators A and B, the Iterator.next() method will return the lesser of A.next() and B.next().
    The comparator is optional. If null is specified then natural order is used.
    
    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:
    
    java.lang.NullPointerException - if either iterator is null
  - collatedIterator
```
public static java.util.Iterator collatedIterator(java.util.Comparator comparator,
                                                  java.util.Iterator[] iterators)
```
    Deprecated.
    
    Gets an iterator that provides an ordered iteration over the elements contained in an array of Iterators.
    Given two ordered Iterators A and B, the Iterator.next() method will return the lesser of A.next() and B.next() and so on.
    The comparator is optional. If null is specified then natural order is used.
    
    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:
    
    java.lang.NullPointerException - if iterators array is null or contains a null
  - collatedIterator
```
public static java.util.Iterator collatedIterator(java.util.Comparator comparator,
                                                  java.util.Collection iterators)
```
    Deprecated.
    
    Gets an iterator that provides an ordered iteration over the elements contained in a collection of Iterators.
    Given two ordered Iterators A and B, the Iterator.next() method will return the lesser of A.next() and B.next() and so on.
    The comparator is optional. If null is specified then natural order is used.
    
    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:
    
    java.lang.NullPointerException - if iterators collection is null or contains a null
    
    java.lang.ClassCastException - if the iterators collection contains the wrong object type
  - objectGraphIterator
```
public static java.util.Iterator objectGraphIterator(java.lang.Object root,
                                                     Transformer transformer)
```
    Deprecated.
    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 Transformer to extract the iterators and elements. Its main benefit is that no intermediate List is created.
    For example, consider an object graph:
    |- Branch -- Leaf | \- Leaf |- Tree | /- Leaf | |- Branch -- Leaf Forest | \- Leaf | |- Branch -- Leaf | | \- Leaf |- Tree | /- Leaf |- Branch -- Leaf |- Branch -- Leaf
    The 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.
    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:
    
    Commons Collections 3.1
  - transformedIterator
```
public static java.util.Iterator transformedIterator(java.util.Iterator iterator,
                                                     Transformer transform)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    iterator - the iterator to use, not null
    
    transform - the transform to use, not null
    
    Returns:
    
    a new transforming iterator
    
    Throws:
    
    java.lang.NullPointerException - if either parameter is null
  - filteredIterator
```
public static java.util.Iterator filteredIterator(java.util.Iterator iterator,
                                                  Predicate predicate)
```
    Deprecated.
    
    Gets an iterator that filters another iterator.
    The returned iterator will only return objects that match the specified filtering predicate.
    
    Parameters:
    
    iterator - the iterator to use, not null
    
    predicate - the predicate to use as a filter, not null
    
    Returns:
    
    a new filtered iterator
    
    Throws:
    
    java.lang.NullPointerException - if either parameter is null
  - filteredListIterator
```
public static java.util.ListIterator filteredListIterator(java.util.ListIterator listIterator,
                                                          Predicate predicate)
```
    Deprecated.
    
    Gets a list iterator that filters another list iterator.
    The returned iterator will only return objects that match the specified filtering predicate.
    
    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:
    
    java.lang.NullPointerException - if either parameter is null
  - loopingIterator
```
public static ResettableIterator loopingIterator(java.util.Collection coll)
```
    Deprecated.
    
    Gets 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.
    
    Parameters:
    
    coll - the collection to iterate over, not null
    
    Returns:
    
    a new looping iterator
    
    Throws:
    
    java.lang.NullPointerException - if the collection is null
  - loopingListIterator
```
public static ResettableListIterator loopingListIterator(java.util.List list)
```
    Deprecated.
    
    Gets 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.
    
    Parameters:
    
    list - the list to iterate over, not null
    
    Returns:
    
    a new looping iterator
    
    Throws:
    
    java.lang.NullPointerException - if the list is null
    
    Since:
    
    Commons Collections 3.2
  - asIterator
```
public static java.util.Iterator asIterator(java.util.Enumeration enumeration)
```
    Deprecated.
    
    Gets an iterator that provides an iterator view of the given enumeration.
    
    Parameters:
    
    enumeration - the enumeration to use
    
    Returns:
    
    a new iterator
  - asIterator
```
public static java.util.Iterator asIterator(java.util.Enumeration enumeration,
                                            java.util.Collection removeCollection)
```
    Deprecated.
    
    Gets an iterator that provides an iterator view of the given enumeration that will remove elements from the specified collection.
    
    Parameters:
    
    enumeration - the enumeration to use
    
    removeCollection - the collection to remove elements from
    
    Returns:
    
    a new iterator
  - asEnumeration
```
public static java.util.Enumeration asEnumeration(java.util.Iterator iterator)
```
    Deprecated.
    
    Gets an enumeration that wraps an iterator.
    
    Parameters:
    
    iterator - the iterator to use, not null
    
    Returns:
    
    a new enumeration
    
    Throws:
    
    java.lang.NullPointerException - if iterator is null
  - toListIterator
```
public static java.util.ListIterator toListIterator(java.util.Iterator iterator)
```
    Deprecated.
    
    Gets 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.
    
    Parameters:
    
    iterator - the iterator to use, not null
    
    Returns:
    
    a new iterator
    
    Throws:
    
    java.lang.NullPointerException - if iterator parameter is null
  - toArray
```
public static java.lang.Object[] toArray(java.util.Iterator iterator)
```
    Deprecated.
    
    Gets 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:
    
    java.lang.NullPointerException - if iterator parameter is null
  - toArray
```
public static java.lang.Object[] toArray(java.util.Iterator iterator,
                                         java.lang.Class arrayClass)
```
    Deprecated.
    
    Gets 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
    
    arrayClass - the class of array to create
    
    Returns:
    
    an array of the iterator contents
    
    Throws:
    
    java.lang.NullPointerException - if iterator parameter is null
    
    java.lang.NullPointerException - if arrayClass is null
    
    java.lang.ClassCastException - if the arrayClass is invalid
  - toList
```
public static java.util.List toList(java.util.Iterator iterator)
```
    Deprecated.
    
    Gets 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.
    
    Parameters:
    
    iterator - the iterator to use, not null
    
    Returns:
    
    a list of the iterator contents
    
    Throws:
    
    java.lang.NullPointerException - if iterator parameter is null
  - toList
```
public static java.util.List toList(java.util.Iterator iterator,
                                    int estimatedSize)
```
    Deprecated.
    
    Gets 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.
    
    Parameters:
    
    iterator - the iterator to use, not null
    
    estimatedSize - the initial size of the ArrayList
    
    Returns:
    
    a list of the iterator contents
    
    Throws:
    
    java.lang.NullPointerException - if iterator parameter is null
    
    java.lang.IllegalArgumentException - if the size is less than 1
  - getIterator
```
public static java.util.Iterator getIterator(java.lang.Object obj)
```
    Deprecated.
    Gets a suitable Iterator for the given object.
    This method can handles 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
    Parameters:
    
    obj - the object to convert to an iterator
    
    Returns:
    
    a suitable iterator, never null

Class IteratorUtils

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

EMPTY_ITERATOR

EMPTY_LIST_ITERATOR

EMPTY_ORDERED_ITERATOR

EMPTY_MAP_ITERATOR

EMPTY_ORDERED_MAP_ITERATOR

Constructor Detail

IteratorUtils

Method Detail

emptyIterator

emptyListIterator

emptyOrderedIterator

emptyMapIterator

emptyOrderedMapIterator

singletonIterator

singletonListIterator

arrayIterator

arrayIterator

arrayIterator

arrayIterator

arrayIterator

arrayIterator

arrayListIterator

arrayListIterator

arrayListIterator

arrayListIterator

arrayListIterator

arrayListIterator

unmodifiableIterator

unmodifiableListIterator

unmodifiableMapIterator

chainedIterator

chainedIterator

chainedIterator

collatedIterator

collatedIterator

collatedIterator

objectGraphIterator

transformedIterator

filteredIterator

filteredListIterator

loopingIterator

loopingListIterator

asIterator

asIterator

asEnumeration

toListIterator

toArray

toArray

toList

toList

getIterator