- All Implemented Interfaces:
public class UnionIterator extends java.lang.Object implements SequenceIterator, LookaheadIteratorA multi-way union delivering the sorted results obtained from a number of sorted input iterators
All Methods Instance Methods Concrete Methods Modifier and Type Method Description
close()Close the iterator.
getProperties()Get properties of this iterator
hasNext()Determine whether there are more items to come.
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
public UnionIterator(java.util.List<SequenceIterator> inputs, ItemOrderComparer comparer) throws XPathExceptionCreate the iterator. The two input iterators must return nodes in document order for this to work.
inputs- iterators over the first operand sequence (in document order)
comparer- used to test whether nodes are in document order. Different versions are used for intra-document and cross-document operations
XPathException- if an error occurs reading the first item of either operand
public boolean hasNext()Description copied from interface:
LookaheadIteratorDetermine 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 property
public NodeInfo next() throws XPathExceptionDescription copied from interface:
SequenceIteratorGet the next item in the sequence. This method changes the state of the iterator.
- Specified by:
- 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.
XPathException- if an error occurs retrieving the next item
public void close()Description copied from interface:
SequenceIteratorClose 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.
public java.util.EnumSet<SequenceIterator.Property> getProperties()Get properties of this iterator
- Specified by:
- the properties of this iterator. This will be some combination of
properties such as
SequenceIterator.Property.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.