Package org.apache.commons.collections

Class IteratorUtils

java.lang.Object
org.apache.commons.collections.IteratorUtils
@Deprecated(since="2021-04-30") public class IteratorUtils extends Object
Deprecated.
Apache Commons Collections version 3.x is being deprecated from AEMaaCS. The upgraded version 4.4 of Commons Collections is already included as replacement. Customers are advised to upgrade to this version of the library. Please note: the package name was changed to org.apache.commons.collections4. Further note that there are AEM APIs currently exposing the old collections classes; these will be updated in upcoming releases.
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 Details

    • 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 Details

    • IteratorUtils

      public IteratorUtils()
      Deprecated.
      IteratorUtils is not normally instantiated.

  • Method Details

    • 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(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 ListIterator singletonListIterator(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(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:
      NullPointerException - if array is null

    • arrayIterator

      public static ResettableIterator arrayIterator(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:
      IllegalArgumentException - if the array is not an array
      NullPointerException - if array is null

    • arrayIterator

      public static ResettableIterator arrayIterator(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:
      IndexOutOfBoundsException - if start is less than zero or greater than the length of the array
      NullPointerException - if array is null

    • arrayIterator

      public static ResettableIterator arrayIterator(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:
      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

    • arrayIterator

      public static ResettableIterator arrayIterator(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:
      IndexOutOfBoundsException - if array bounds are invalid
      IllegalArgumentException - if end is before start
      NullPointerException - if array is null

    • arrayIterator

      public static ResettableIterator arrayIterator(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:
      IllegalArgumentException - if the array is not an array
      IndexOutOfBoundsException - if array bounds are invalid
      IllegalArgumentException - if end is before start
      NullPointerException - if array is null

    • arrayListIterator

      public static ResettableListIterator arrayListIterator(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:
      NullPointerException - if array is null

    • arrayListIterator

      public static ResettableListIterator arrayListIterator(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:
      IllegalArgumentException - if the array is not an array
      NullPointerException - if array is null

    • arrayListIterator

      public static ResettableListIterator arrayListIterator(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:
      IndexOutOfBoundsException - if start is less than zero
      NullPointerException - if array is null

    • arrayListIterator

      public static ResettableListIterator arrayListIterator(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:
      IllegalArgumentException - if the array is not an array
      IndexOutOfBoundsException - if start is less than zero
      NullPointerException - if array is null

    • arrayListIterator

      public static ResettableListIterator arrayListIterator(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:
      IndexOutOfBoundsException - if array bounds are invalid
      IllegalArgumentException - if end is before start
      NullPointerException - if array is null

    • arrayListIterator

      public static ResettableListIterator arrayListIterator(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:
      IllegalArgumentException - if the array is not an array
      IndexOutOfBoundsException - if array bounds are invalid
      IllegalArgumentException - if end is before start
      NullPointerException - if array is null

    • unmodifiableIterator

      public static Iterator unmodifiableIterator(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 ListIterator unmodifiableListIterator(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 Iterator chainedIterator(Iterator iterator1, 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:
      NullPointerException - if either iterator is null

    • chainedIterator

      public static Iterator chainedIterator(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:
      NullPointerException - if iterators array is null or contains a null

    • chainedIterator

      public static Iterator chainedIterator(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:
      NullPointerException - if iterators collection is null or contains a null
      ClassCastException - if the iterators collection contains the wrong object type

    • collatedIterator

      public static Iterator collatedIterator(Comparator comparator, Iterator iterator1, 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:
      NullPointerException - if either iterator is null

    • collatedIterator

      public static Iterator collatedIterator(Comparator comparator, 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:
      NullPointerException - if iterators array is null or contains a null

    • collatedIterator

      public static Iterator collatedIterator(Comparator comparator, 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:
      NullPointerException - if iterators collection is null or contains a null
      ClassCastException - if the iterators collection contains the wrong object type

    • objectGraphIterator

      public static Iterator objectGraphIterator(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 Iterator transformedIterator(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:
      NullPointerException - if either parameter is null

    • filteredIterator

      public static Iterator filteredIterator(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:
      NullPointerException - if either parameter is null

    • filteredListIterator

      public static ListIterator filteredListIterator(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:
      NullPointerException - if either parameter is null

    • loopingIterator

      public static ResettableIterator loopingIterator(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:
      NullPointerException - if the collection is null

    • loopingListIterator

      public static ResettableListIterator loopingListIterator(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:
      NullPointerException - if the list is null
      Since:
      Commons Collections 3.2

    • asIterator

      public static Iterator asIterator(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 Iterator asIterator(Enumeration enumeration, 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 Enumeration asEnumeration(Iterator iterator)
      Deprecated.
      Gets an enumeration that wraps an iterator.
      Parameters:
      iterator - the iterator to use, not null
      Returns:
      a new enumeration
      Throws:
      NullPointerException - if iterator is null

    • toListIterator

      public static ListIterator toListIterator(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:
      NullPointerException - if iterator parameter is null

    • toArray

      public static Object[] toArray(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:
      NullPointerException - if iterator parameter is null

    • toArray

      public static Object[] toArray(Iterator iterator, 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:
      NullPointerException - if iterator parameter is null
      NullPointerException - if arrayClass is null
      ClassCastException - if the arrayClass is invalid

    • toList

      public static List toList(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:
      NullPointerException - if iterator parameter is null

    • toList

      public static List toList(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:
      NullPointerException - if iterator parameter is null
      IllegalArgumentException - if the size is less than 1

    • getIterator

      public static Iterator getIterator(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