net.sf.saxon.om
Class ReverseArrayIterator

java.lang.Object
  net.sf.saxon.om.ReverseArrayIterator

All Implemented Interfaces:

LastPositionFinder, ReversibleIterator, LookaheadIterator, SequenceIterator, UnfailingIterator

Direct Known Subclasses:

ReverseNodeArrayIterator

public class ReverseArrayIterator
extends Object
implements UnfailingIterator, ReversibleIterator, LookaheadIterator, LastPositionFinder

ReverseArrayIterator is used to enumerate items held in an array in reverse order.

Author:

Michael H. Kay

Field Summary

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

GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

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

GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

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

GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

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

GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Constructor Summary

ReverseArrayIterator(Item[] items, int start, int end)
Create an iterator a slice of an array

Method Summary

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	getLastPosition() Get the last position (that is, the number of items in the sequence).
int	getProperties() Get properties of this iterator, as a bit-significant integer.
SequenceIterator	getReverseIterator() Get an iterator that processes the same items in reverse order.
boolean	hasNext() Determine whether there are more items to come.
Item	next() Get the next item in the sequence.
int	position() Get the current position.

Methods inherited from class java.lang.Object

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

Constructor Detail

ReverseArrayIterator

public ReverseArrayIterator(Item[] items,
                            int start,
                            int end)

Create an iterator a slice of an array

Parameters:

items - The array of items

start - The first item in the array to be be used (this will be the last one in the resulting iteration). Zero-based.

end - The item after the last one in the array to be used (this will be the first one to be returned by the iterator). Zero-based.

Method Detail

hasNext

public boolean hasNext()

Determine whether there are more items to come. Note that this operation is stateless and it is not necessary (or usual) to call it before calling next(). It is used only when there is an explicit need to tell if we are at the last element.

Specified by:

hasNext in interface LookaheadIterator

Returns:

true if there are more items in the sequence

next

public Item next()

Description copied from interface: SequenceIterator

Get the next item in the sequence. This method changes the state of the iterator, in particular it affects the result of subsequent calls of position() and current().

Specified by:

next in interface SequenceIterator

Specified by:

next in interface UnfailingIterator

Returns:

the next item, or null if there are no more items. Once a call on next() has returned null, no further calls should be made. The preferred action for an iterator if subsequent calls on next() are made is to return null again, and all implementations within Saxon follow this rule.

current

public Item current()

Description copied from interface: SequenceIterator

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(). This method does not change the state of the iterator.

Specified by:

current in interface SequenceIterator

Specified by:

current in interface UnfailingIterator

Returns:

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

position

public int position()

Description copied from interface: SequenceIterator

Get the current position. This will usually be zero before the first call on next(), otherwise it will be the number of times that next() has been called. Once next() has returned null, the preferred action is for subsequent calls on position() to return -1, but not all existing implementations follow this practice. (In particular, the EmptyIterator is stateless, and always returns 0 as the value of position(), whether or not next() has been called.)

This method does not change the state of the iterator.

Specified by:

position in interface SequenceIterator

Specified by:

position in interface UnfailingIterator

Returns:

the current position, the position of the item returned by the most recent call of next(). This is 1 after next() has been successfully called once, 2 after it has been called twice, and so on. If next() has never been called, the method returns zero. If the end of the sequence has been reached, the value returned will always be <= 0; the preferred value is -1.

getLastPosition

public int getLastPosition()

Description copied from interface: LastPositionFinder

Get the last position (that is, the number of items in the sequence). This method is non-destructive: it does not change the state of the iterator. The result is undefined if the next() method of the iterator has already returned null. This method must not be called unless the result of getProperties() on the iterator includes the bit setting SequenceIterator.LAST_POSITION_FINDER

Specified by:

getLastPosition in interface LastPositionFinder

getAnother

public SequenceIterator getAnother()

Description copied from interface: SequenceIterator

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

This method allows access to all the items in the sequence without disturbing the current position of the iterator. Internally, its main use is in evaluating the last() function.

This method does not change the state of the iterator.

Specified by:

getAnother in interface SequenceIterator

Specified by:

getAnother in interface UnfailingIterator

Returns:

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

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.

getReverseIterator

public SequenceIterator getReverseIterator()

Get an iterator that processes the same items in reverse order. Since this iterator is processing the items backwards, this method returns an ArrayIterator that processes them forwards.

Specified by:

getReverseIterator in interface ReversibleIterator

Returns:

a new ArrayIterator