org.apache.commons.collections.iterators
Class CollatingIterator

java.lang.Object
  org.apache.commons.collections.iterators.CollatingIterator

All Implemented Interfaces:

java.util.Iterator

public class CollatingIterator
extends java.lang.Object
implements java.util.Iterator

Provides an ordered iteration over the elements contained in a collection of ordered Iterators.

Given two ordered Iterator instances A and B, the next() method on this iterator will return the lesser of A.next() and B.next().

Since:

Commons Collections 2.1

Version:

$Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $

Author:

Rodney Waldhoff, Stephen Colebourne

Constructor Summary

CollatingIterator()
Constructs a new CollatingIterator.

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

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

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

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

CollatingIterator(java.util.Comparator comp, java.util.Iterator a, java.util.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(java.util.Iterator iterator) Adds the given Iterator to the iterators being collated.
java.util.Comparator	getComparator() Gets the Comparator by which collatation occurs.
java.util.List	getIterators() Gets the list of Iterators (unmodifiable).
boolean	hasNext() Returns true if any child iterator has remaining elements.
java.lang.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(java.util.Comparator comp) Sets the Comparator by which collation occurs.
void	setIterator(int index, java.util.Iterator iterator) Sets 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(java.util.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 to sort, or null to use natural sort order

CollatingIterator

public CollatingIterator(java.util.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 to sort, or null to use natural sort order

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

CollatingIterator

public CollatingIterator(java.util.Comparator comp,
                         java.util.Iterator a,
                         java.util.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:

java.lang.NullPointerException - if either iterator is null

CollatingIterator

public CollatingIterator(java.util.Comparator comp,
                         java.util.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:

java.lang.NullPointerException - if iterators array is or contains null

CollatingIterator

public CollatingIterator(java.util.Comparator comp,
                         java.util.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:

java.lang.NullPointerException - if the iterators collection is or contains null

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

Method Detail

addIterator

public void addIterator(java.util.Iterator iterator)

Adds the given Iterator to the iterators being collated.

Parameters:

iterator - the iterator to add to the collation, must not be null

Throws:

java.lang.IllegalStateException - if iteration has started

java.lang.NullPointerException - if the iterator is null

setIterator

public void setIterator(int index,
                        java.util.Iterator iterator)

Sets the iterator at the given index.

Parameters:

index - index of the Iterator to replace

iterator - Iterator to place at the given index

Throws:

java.lang.IndexOutOfBoundsException - if index < 0 or index > size()

java.lang.IllegalStateException - if iteration has started

java.lang.NullPointerException - if the iterator is null

getIterators

public java.util.List getIterators()

Gets the list of Iterators (unmodifiable).

Returns:

the unmodifiable list of iterators added

getComparator

public java.util.Comparator getComparator()

Gets the Comparator by which collatation occurs.

setComparator

public void setComparator(java.util.Comparator comp)

Sets the Comparator by which collation occurs.

Throws:

java.lang.IllegalStateException - if iteration has started

hasNext

public boolean hasNext()

Returns true if any child iterator has remaining elements.

Specified by:

hasNext in interface java.util.Iterator

Returns:

true if this iterator has remaining elements

next

public java.lang.Object next()
                      throws java.util.NoSuchElementException

Returns the next ordered element from a child iterator.

Specified by:

next in interface java.util.Iterator

Returns:

the next ordered element

Throws:

java.util.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 java.util.Iterator

Throws:

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