net.sf.saxon.expr

Class DifferenceEnumeration

java.lang.Object

net.sf.saxon.expr.DifferenceEnumeration

All Implemented Interfaces:

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

public class DifferenceEnumeration
extends java.lang.Object
implements SequenceIterator

An enumeration representing a nodeset that is teh difference of two other NodeSets. There is an "except" operator in XPath 2.0 to create such an expression.

Constructor Summary

Constructors

Constructor and Description
DifferenceEnumeration(SequenceIterator p1, SequenceIterator p2, java.util.Comparator<? super NodeInfo> comparer) Form an enumeration of the difference of two nodesets, that is, the nodes that are in p1 and that are not in p2.

Method Summary

Modifier and Type	Method and Description
void	close() Close the iterator.
void	discharge() Calling this method instructs the iterator to release any resources it holds, while still remaining able to deliver the remaining items in the sequence.
NodeInfo	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

Constructor Detail

DifferenceEnumeration

public DifferenceEnumeration(SequenceIterator p1,
                             SequenceIterator p2,
                             java.util.Comparator<? super NodeInfo> comparer)
                      throws XPathException

Form an enumeration of the difference of two nodesets, that is, the nodes that are in p1 and that are not in p2.

Parameters:

p1 - the first operand, with nodes delivered in document order

p2 - the second operand, with nodes delivered in document order

comparer - the comparer

Throws:

XPathException - if a failure occurs reading from either input sequence

Method Detail

next

public NodeInfo next()

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.

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.

Closing an iterator is not necessary if the iterator is read to completion: if a call on SequenceIterator.next() returns null, the iterator will be closed automatically. An explicit call on SequenceIterator.close() is needed only when iteration is abandoned prematurely.

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface SequenceIterator

discharge

public void discharge()

Description copied from interface: SequenceIterator

Calling this method instructs the iterator to release any resources it holds, while still remaining able to deliver the remaining items in the sequence. This may require the iterator to calculate the rest of the sequence eagerly. The method is called by a client if it anticipates that it might not read the iterator to completion, but it cannot guarantee that SequenceIterator.close() will be called when no more items are needed.

Specified by:

discharge in interface SequenceIterator