net.sf.saxon.tree.iter

Class LookaheadIteratorImpl

java.lang.Object

net.sf.saxon.tree.iter.LookaheadIteratorImpl

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, SequenceIterator, LookaheadIterator

public class LookaheadIteratorImpl
extends java.lang.Object
implements LookaheadIterator

This class wraps any sequence iterator, turning it into a lookahead iterator, by looking ahead one item

Field Summary

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

ATOMIZING, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Method Summary

Modifier and Type	Method and Description
void	close() Close the iterator.
int	getProperties() Get properties of this iterator, as a bit-significant integer.
boolean	hasNext() Determine whether there are more items to come.
static LookaheadIterator	makeLookaheadIterator(SequenceIterator base)
Item	next() Get the next item in the sequence.

Methods inherited from class java.lang.Object

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

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

forEachOrFail, materialize

Method Detail

makeLookaheadIterator

public static LookaheadIterator makeLookaheadIterator(SequenceIterator base)
                                               throws XPathException

Throws:

XPathException

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.

This method must not be called unless the result of getProperties() on the iterator includes the bit setting SequenceIterator.LOOKAHEAD

Specified by:

hasNext in interface LookaheadIterator

Returns:

true if there are more items in the sequence

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.

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

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.

For example, the iterator returned by the unparsed-text-lines() function has a close() method that causes the underlying input stream to be closed, whether or not the file has been read to completion.

Closing an iterator is important 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 java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface SequenceIterator

getProperties

public int getProperties()

Description copied from interface: SequenceIterator

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.