org.apache.commons.collections.iterators
Class CollatingIterator

java.lang.Object
  |
  +--org.apache.commons.collections.iterators.CollatingIterator

public class CollatingIterator

extends Object

implements Iterator

Provides an ordered iteration over the elements contained in a collection of ordered Iterators. In other words, given two ordered Iterators A and B, my next() method will return the lesser of A.next() and B.next().

Since:

2.1

Version:

$Revision: 1.3 $ $Date: 2002/09/07 00:28:53 $

Author:

Rodney Waldhoff, Stephen Colebourne

Constructor Summary

CollatingIterator()
Constructs a new CollatingIterator.

CollatingIterator(Comparator comp)
Constructs a new CollatingIterator that will used the specified comparator for ordering.

CollatingIterator(Comparator comp, Collection iterators)
Constructs a new CollatingIterator that will use the specified comparator to provide ordered iteration over the collection of iterators.

CollatingIterator(Comparator comp, int initIterCapacity)
Constructs a new CollatingIterator that will used the specified comparator for ordering and have the specified initial capacity.

CollatingIterator(Comparator comp, Iterator[] iterators)
Constructs a new CollatingIterator that will use the specified comparator to provide ordered iteration over the array of iterators.

CollatingIterator(Comparator comp, Iterator a, Iterator b)
Constructs a new CollatingIterator that will use the specified comparator to provide ordered iteration over the two given iterators.

Method Summary

void	addIterator(Iterator iterator) Add the given Iterator to my collection to collate.
Comparator	getComparator() Get the Comparator by which I collate.
List	getIterators() Get the list of Iterators (unmodifiable)
boolean	hasNext() Returns true if any child iterator has remaining elements.
Object	next() Returns the next ordered element from a child iterator.
void	remove() Removes the last returned element from the child iterator that produced it.
void	setComparator(Comparator comp) Set the Comparator by which I collate.
void	setIterator(int index, Iterator iterator) Set the Iterator at the given index

Methods inherited from class java.lang.Object

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

Constructor Detail

CollatingIterator

public CollatingIterator()

Constructs a new CollatingIterator. Natural sort order will be used, and child iterators will have to be manually added using the addIterator(Iterator) method.

CollatingIterator

public CollatingIterator(Comparator comp)

Constructs a new CollatingIterator that will used the specified comparator for ordering. Child iterators will have to be manually added using the addIterator(Iterator) method.

Parameters:

comp - the comparator to use for ordering, or null to use natural sort order

CollatingIterator

public CollatingIterator(Comparator comp,
                         int initIterCapacity)

Constructs a new CollatingIterator that will used the specified comparator for ordering and have the specified initial capacity. Child iterators will have to be manually added using the addIterator(Iterator) method.

Parameters:

comp - the comparator to use for ordering, or null to use natural sort order

initIterCapacity - the initial capacity for the internal list of child iterators

CollatingIterator

public CollatingIterator(Comparator comp,
                         Iterator a,
                         Iterator b)

Constructs a new CollatingIterator that will use the specified comparator to provide ordered iteration over the two given iterators.

Parameters:

comp - the comparator to use to sort, or null to use natural sort order

a - the first child ordered iterator

b - the second child ordered iterator

Throws:

NullPointerException - if either iterator is null

CollatingIterator

public CollatingIterator(Comparator comp,
                         Iterator[] iterators)

Constructs a new CollatingIterator that will use the specified comparator to provide ordered iteration over the array of iterators.

Parameters:

comp - the comparator to use to sort, or null to use natural sort order

iterators - the array of iterators

Throws:

NullPointerException - if iterators array is or contains null

CollatingIterator

public CollatingIterator(Comparator comp,
                         Collection iterators)

Constructs a new CollatingIterator that will use the specified comparator to provide ordered iteration over the collection of iterators.

Parameters:

comp - the comparator to use to sort, or null to use natural sort order

iterators - the collection of iterators

Throws:

NullPointerException - if the iterators collection is or contains null

ClassCastException - if the iterators collection contains an element that's not an Iterator

Method Detail

addIterator

public void addIterator(Iterator iterator)

Add the given Iterator to my collection to collate.

Throws:

IllegalStateException - if I've already started iterating

NullPointerException - if the iterator is null

setIterator

public void setIterator(int index,
                        Iterator iterator)
                 throws IndexOutOfBoundsException

Set the Iterator at the given index

Parameters:

index - index of the Iterator to replace

iterator - Iterator to place at the given index

Throws:

IndexOutOfBoundsException - if index < 0 or index > size()

IllegalStateException - if I've already started iterating

NullPointerException - if the iterator is null

getIterators

public List getIterators()

Get the list of Iterators (unmodifiable)

Returns:

the unmodifiable list of iterators added

setComparator

public void setComparator(Comparator comp)

Set the Comparator by which I collate.

Throws:

IllegalStateException - if I've already started iterating

getComparator

public Comparator getComparator()

Get the Comparator by which I collate.

hasNext

public boolean hasNext()

Returns true if any child iterator has remaining elements.

Specified by:

hasNext in interface Iterator

Returns:

true if this iterator has remaining elements

next

public Object next()
            throws NoSuchElementException

Returns the next ordered element from a child iterator.

Specified by:

next in interface Iterator

Returns:

the next ordered element

Throws:

NoSuchElementException - if no child iterator has any more elements

remove

public void remove()

Removes the last returned element from the child iterator that produced it.

Specified by:

remove in interface Iterator

Throws:

IllegalStateException - if there is no last returned element, or if the last returned element has already been removed