net.sf.saxon.expr
Class UnionEnumeration
java.lang.Object
net.sf.saxon.expr.UnionEnumeration
- All Implemented Interfaces:
- LookaheadIterator, SequenceIterator
- public class UnionEnumeration
- extends java.lang.Object
- implements SequenceIterator, LookaheadIterator
An enumeration representing a nodeset that is a union of two other NodeSets.
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. |
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 |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
UnionEnumeration
public UnionEnumeration(SequenceIterator p1,
SequenceIterator p2,
NodeOrderComparer comparer)
throws XPathException
- Create the iterator. The two input iterators must return nodes in document
order for this to work.
hasNext
public boolean hasNext()
- Description copied from interface:
LookaheadIterator
- 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 nodes
next
public Item next()
throws XPathException
- 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
- 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.
- Throws:
XPathException
- if an error occurs retrieving the next item
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
- 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
- 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.
getAnother
public SequenceIterator getAnother()
throws XPathException
- 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
- Returns:
- a SequenceIterator that iterates over the same items,
positioned before the first item
- Throws:
XPathException
- if any error occurs