Class GroupAdjacentIterator
- All Implemented Interfaces:
Closeable
,AutoCloseable
,LastPositionFinder
,GroupIterator
,SequenceIterator
,LookaheadIterator
Each step of this iterator advances to the first item of the next group, leaving the members of that group in a saved list.
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Nested Class Summary
Nested classes/interfaces inherited from interface net.sf.saxon.om.SequenceIterator
SequenceIterator.Property
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Constructor Summary
ConstructorsConstructorDescriptionGroupAdjacentIterator
(Expression select, Expression keyExpression, XPathContext baseContext, StringCollator collator, boolean composite) -
Method Summary
Modifier and TypeMethodDescriptionvoid
close()
Close the iterator.Get the grouping key of the current groupint
Get the last position (that is, the number of items in the sequence).Get properties of this iterator, as a bit-significant integer.boolean
hasNext()
Determine whether there are more items to come.Get an iterator over the members of the current group, in population order.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
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Constructor Details
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GroupAdjacentIterator
public GroupAdjacentIterator(Expression select, Expression keyExpression, XPathContext baseContext, StringCollator collator, boolean composite) throws XPathException - Throws:
XPathException
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Method Details
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getLength
Description copied from interface:LastPositionFinder
Get the last position (that is, the number of items in the sequence). This method is non-destructive: it does not change the state of the iterator. The result is undefined if the next() method of the iterator has already returned null. This method must not be called unless the result of getProperties() on the iterator includes the bit settingSequenceIterator.Property.LAST_POSITION_FINDER
- Specified by:
getLength
in interfaceLastPositionFinder
- Returns:
- the number of items in the sequence
- Throws:
XPathException
- if an error occurs evaluating the sequence in order to determine the number of items
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getCurrentGroupingKey
Description copied from interface:GroupIterator
Get the grouping key of the current group- Specified by:
getCurrentGroupingKey
in interfaceGroupIterator
- Returns:
- the current grouping key in the case of group-by or group-adjacent, or null in the case of group-starting-with and group-ending-with
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iterateCurrentGroup
Description copied from interface:GroupIterator
Get an iterator over the members of the current group, in population order. This must always be a clean iterator, that is, an iterator that starts at the first item of the group.- Specified by:
iterateCurrentGroup
in interfaceGroupIterator
- Returns:
- an iterator over all the members of the current group, in population order.
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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 property
SequenceIterator.Property.LOOKAHEAD
- Specified by:
hasNext
in interfaceLookaheadIterator
- Returns:
- true if there are more items in the sequence
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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 interfaceSequenceIterator
- 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
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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 interfaceAutoCloseable
- Specified by:
close
in interfaceCloseable
- Specified by:
close
in interfaceSequenceIterator
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getProperties
Get properties of this iterator, as a bit-significant integer.- Specified by:
getProperties
in interfaceSequenceIterator
- Returns:
- the properties of this iterator. This will be some combination of
properties such as
SequenceIterator.Property.GROUNDED
,SequenceIterator.Property.LAST_POSITION_FINDER
, andSequenceIterator.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.
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