net.sf.saxon.om

Class LazySequence

java.lang.Object

net.sf.saxon.om.LazySequence

All Implemented Interfaces:

Sequence

public class LazySequence
extends java.lang.Object
implements Sequence

A sequence that wraps an iterator, without being materialized. It can only be used once.

See Also:

SequenceTool.makeRepeatable(net.sf.saxon.om.Sequence)

Constructor Summary

Constructors

Constructor and Description
LazySequence(SequenceIterator iterator) Create a virtual sequence backed by an iterator

Method Summary

Modifier and Type	Method and Description
Item	head() Get the first item in the sequence.
SequenceIterator	iterate() Iterate over all the items in the sequence.

Methods inherited from class java.lang.Object

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

Constructor Detail

LazySequence

public LazySequence(SequenceIterator iterator)

Create a virtual sequence backed by an iterator

Parameters:

iterator - the iterator that delivers the items in the sequence

Method Detail

head

public Item head()
          throws XPathException

Get the first item in the sequence. This calls iterate() internally, which means it can only be called once; the method should only be used if the client requires only the first item in the sequence (or knows that the sequence has length one).

Specified by:

head in interface Sequence

Returns:

the first item, or null if the sequence is empty

Throws:

XPathException

iterate

public SequenceIterator iterate()
                         throws XPathException

Iterate over all the items in the sequence. The first time this is called it returns the original iterator backing the sequence. On subsequent calls it clones the original iterator.

Specified by:

iterate in interface Sequence

Returns:

an iterator over the items in the sequence

Throws:

XPathException - if evaluation of the iterator fails.

java.lang.IllegalStateException - if iterate() has already been called