public class MergeIterator extends java.lang.Object implements SequenceIterator, LookaheadIterator
Constructor and Description |
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MergeIterator(SequenceIterator p1,
SequenceIterator p2,
java.util.Comparator<ObjectValue<ItemWithMergeKeys>> comparer)
Create the iterator.
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Modifier and Type | Method and Description |
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void |
close()
Close the iterator.
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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.
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boolean |
hasNext()
Determine whether there are more items to come.
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ObjectValue<ItemWithMergeKeys> |
next()
Get the next item in the sequence.
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boolean |
supportsHasNext()
Ask whether the hasNext() method can be called.
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public MergeIterator(SequenceIterator p1, SequenceIterator p2, java.util.Comparator<ObjectValue<ItemWithMergeKeys>> comparer) throws XPathException
p1
- iterator over the first operand sequence (in document order)p2
- iterator over the second operand sequencecomparer
- used to test whether nodes are in document order. Different versions
are used for intra-document and cross-document operationsXPathException
- if an error occurs reading from either input iteratorpublic boolean supportsHasNext()
LookaheadIterator
supportsHasNext
in interface LookaheadIterator
LookaheadIterator.hasNext()
method is availablepublic boolean hasNext()
LookaheadIterator
This method must not be called unless the result of LookaheadIterator.supportsHasNext()
is true.
hasNext
in interface LookaheadIterator
public ObjectValue<ItemWithMergeKeys> next()
SequenceIterator
next
in interface SequenceIterator
public void close()
SequenceIterator
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.
close
in interface java.io.Closeable
close
in interface java.lang.AutoCloseable
close
in interface SequenceIterator
public void discharge()
SequenceIterator
SequenceIterator.close()
will be called when no more items are needed.discharge
in interface SequenceIterator
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