org.apache.commons.collections.iterators
Class FilterIterator

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

All Implemented Interfaces:

java.util.Iterator

Direct Known Subclasses:

UniqueFilterIterator

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

Decorates another Iterator using a predicate to filter elements.

This iterator decorates the underlying iterator, only allowing through those elements that match the specified Predicate.

Since:

Commons Collections 1.0

Version:

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

Author:

James Strachan, Jan Sorensen, Ralph Wagner, Stephen Colebourne

Constructor Summary

FilterIterator()
Constructs a new FilterIterator that will not function until setIterator is invoked.

FilterIterator(java.util.Iterator iterator)
Constructs a new FilterIterator that will not function until setPredicate is invoked.

FilterIterator(java.util.Iterator iterator, Predicate predicate)
Constructs a new FilterIterator that will use the given iterator and predicate.

Method Summary

java.util.Iterator	getIterator() Gets the iterator this iterator is using.
Predicate	getPredicate() Gets the predicate this iterator is using.
boolean	hasNext() Returns true if the underlying iterator contains an object that matches the predicate.
java.lang.Object	next() Returns the next object that matches the predicate.
void	remove() Removes from the underlying collection of the base iterator the last element returned by this iterator.
void	setIterator(java.util.Iterator iterator) Sets the iterator for this iterator to use.
void	setPredicate(Predicate predicate) Sets the predicate this the iterator to use.

Methods inherited from class java.lang.Object

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

Constructor Detail

FilterIterator

public FilterIterator()

Constructs a new FilterIterator that will not function until setIterator is invoked.

FilterIterator

public FilterIterator(java.util.Iterator iterator)

Constructs a new FilterIterator that will not function until setPredicate is invoked.

Parameters:

iterator - the iterator to use

FilterIterator

public FilterIterator(java.util.Iterator iterator,
                      Predicate predicate)

Constructs a new FilterIterator that will use the given iterator and predicate.

Parameters:

iterator - the iterator to use

predicate - the predicate to use

Method Detail

hasNext

public boolean hasNext()

Returns true if the underlying iterator contains an object that matches the predicate.

Specified by:

hasNext in interface java.util.Iterator

Returns:

true if there is another object that matches the predicate

Throws:

java.lang.NullPointerException - if either the iterator or predicate are null

next

public java.lang.Object next()

Returns the next object that matches the predicate.

Specified by:

next in interface java.util.Iterator

Returns:

the next object which matches the given predicate

Throws:

java.lang.NullPointerException - if either the iterator or predicate are null

java.util.NoSuchElementException - if there are no more elements that match the predicate

remove

public void remove()

Removes from the underlying collection of the base iterator the last element returned by this iterator. This method can only be called if next() was called, but not after hasNext(), because the hasNext() call changes the base iterator.

Specified by:

remove in interface java.util.Iterator

Throws:

java.lang.IllegalStateException - if hasNext() has already been called.

getIterator

public java.util.Iterator getIterator()

Gets the iterator this iterator is using.

Returns:

the iterator

setIterator

public void setIterator(java.util.Iterator iterator)

Sets the iterator for this iterator to use. If iteration has started, this effectively resets the iterator.

Parameters:

iterator - the iterator to use

getPredicate

public Predicate getPredicate()

Gets the predicate this iterator is using.

Returns:

the predicate

setPredicate

public void setPredicate(Predicate predicate)

Sets the predicate this the iterator to use.

Parameters:

predicate - the predicate to use