net.sf.saxon.functions
Class DistinctValues.DistinctIterator

java.lang.Object
  net.sf.saxon.functions.DistinctValues.DistinctIterator

All Implemented Interfaces:

SequenceIterator

Enclosing class:

DistinctValues

public static class DistinctValues.DistinctIterator
extends Object
implements SequenceIterator

Iterator class to return the distinct values in a sequence

Field Summary

Fields inherited from interface net.sf.saxon.om.SequenceIterator

GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Constructor Summary

DistinctValues.DistinctIterator(SequenceIterator base, AtomicComparer comparer)
Create an iterator over the distinct values in a sequence

Method Summary

void	close() Close the iterator.
Item	current() Get the current value in the sequence (the one returned by the most recent call on next()).
SequenceIterator	getAnother() Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.
int	getProperties() Get properties of this iterator, as a bit-significant integer.
Item	next() Get the next item in the sequence.
int	position() Get the current position.

Methods inherited from class java.lang.Object

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

Constructor Detail

DistinctValues.DistinctIterator

public DistinctValues.DistinctIterator(SequenceIterator base,
                                       AtomicComparer comparer)

Create an iterator over the distinct values in a sequence

Parameters:

base - the input sequence. This must return atomic values only.

comparer - The comparer used to obtain comparison keys from each value; these comparison keys are themselves compared using equals().

Method Detail

next

public Item next()
          throws XPathException

Get the next item in the sequence.

Specified by:

next in interface SequenceIterator

Returns:

the next item, or null if there are no more items.

Throws:

XPathException - if an error occurs retrieving the next item

current

public Item current()

Get the current value in the sequence (the one returned by the most recent call on next()). This will be null before the first call of next().

Specified by:

current in interface SequenceIterator

Returns:

the current item, the one most recently returned by a call on next(); or null, if next() has not been called, or if the end of the sequence has been reached.

position

public int position()

Get the current position. This will be zero before the first call on next(), otherwise it will be the number of times that next() has been called.

Specified by:

position in interface SequenceIterator

Returns:

the current position, the position of the item returned by the most recent call of next()

close

public void close()

Description copied from interface: SequenceIterator

Close the iterator. This indicates to the supplier of the data that the client does not require any more items to be delivered by the iterator. This may enable the supplier to release resources. After calling close(), no further calls on the iterator should be made; if further calls are made, the effect of such calls is undefined.

(Currently, closing an iterator is important only when the data is being "pushed" in another thread. Closing the iterator terminates that thread and means that it needs to do no additional work. Indeed, failing to close the iterator may cause the push thread to hang waiting for the buffer to be emptied.)

Specified by:

close in interface SequenceIterator

getAnother

public SequenceIterator getAnother()
                            throws XPathException

Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.

Specified by:

getAnother in interface SequenceIterator

Returns:

a SequenceIterator that iterates over the same items, positioned before the first item

Throws:

XPathException - if any error occurs

getProperties

public int getProperties()

Get properties of this iterator, as a bit-significant integer.

Specified by:

getProperties in interface SequenceIterator

Returns:

the properties of this iterator. This will be some combination of properties such as SequenceIterator.GROUNDED, SequenceIterator.LAST_POSITION_FINDER, and SequenceIterator.LOOKAHEAD. It is always acceptable to return the value zero, indicating that there are no known special properties. It is acceptable for the properties of the iterator to change depending on its state.