Package net.sf.saxon.expr
Class FilterIterator
- java.lang.Object
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- net.sf.saxon.expr.FilterIterator
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- All Implemented Interfaces:
SequenceIterator
- Direct Known Subclasses:
FilterIterator.Leading
,FilterIterator.NonNumeric
public class FilterIterator extends java.lang.Object implements SequenceIterator
A FilterIterator filters an input sequence using a filter expression. Note that a FilterIterator is not used where the filter is a constant number (PositionFilter is used for this purpose instead), so this class does no optimizations for numeric predicates.
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
FilterIterator.Leading
Subclass to support the extension function saxon:leading, which terminates the iteration at the first item whose predicate is falsestatic class
FilterIterator.NonNumeric
Subclass to handle the common special case where it is statically known that the filter cannot return a numeric value
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Field Summary
Fields Modifier and Type Field Description protected SequenceIterator
base
protected Expression
filter
protected XPathContext
filterContext
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Fields inherited from interface net.sf.saxon.om.SequenceIterator
ATOMIZABLE, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD
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Constructor Summary
Constructors Constructor Description FilterIterator(SequenceIterator base, Expression filter, XPathContext context)
Constructor
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description Item
current()
Get the current value in the sequence (the one returned by the most recent call on next()).SequenceIterator
getAnother()
Get another iterator to return the same nodesprotected Item
getNextMatchingItem()
Get the next node that matches the filter predicate if there is one, or null if not.int
getProperties()
Get properties of this iterator, as a bit-significant integer.protected boolean
matches()
Determine whether the context item matches the filter predicateItem
next()
Get the next item if there is oneint
position()
Get the current position.void
setFilterIsSingletonBoolean(boolean isBoolean)
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Field Detail
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base
protected SequenceIterator base
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filter
protected Expression filter
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filterContext
protected XPathContext filterContext
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Constructor Detail
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FilterIterator
public FilterIterator(SequenceIterator base, Expression filter, XPathContext context)
Constructor- Parameters:
base
- An iteration of the items to be filteredfilter
- The expression defining the filter predicatecontext
- The context in which the expression is being evaluated
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Method Detail
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setFilterIsSingletonBoolean
public void setFilterIsSingletonBoolean(boolean isBoolean)
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next
public Item next() throws XPathException
Get the next item if there is one- 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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getNextMatchingItem
protected Item getNextMatchingItem() throws XPathException
Get the next node that matches the filter predicate if there is one, or null if not.- Throws:
XPathException
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matches
protected boolean matches() throws XPathException
Determine whether the context item matches the filter predicate- Throws:
XPathException
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current
public Item current()
Description copied from interface:SequenceIterator
Get the current value in the sequence (the one returned by the most recent call on next()). This will be null before the first call of next(). This method does not change the state of the iterator.- Specified by:
current
in interfaceSequenceIterator
- Returns:
- the current item, the one most recently returned by a call on next(). Returns null if next() has not been called, or if the end of the sequence has been reached.
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position
public int position()
Description copied from interface:SequenceIterator
Get the current position. This will usually be zero before the first call on next(), otherwise it will be the number of times that next() has been called. Once next() has returned null, the preferred action is for subsequent calls on position() to return -1, but not all existing implementations follow this practice. (In particular, the EmptyIterator is stateless, and always returns 0 as the value of position(), whether or not next() has been called.)This method does not change the state of the iterator.
- Specified by:
position
in interfaceSequenceIterator
- Returns:
- the current position, the position of the item returned by the most recent call of next(). This is 1 after next() has been successfully called once, 2 after it has been called twice, and so on. If next() has never been called, the method returns zero. If the end of the sequence has been reached, the value returned will always be <= 0; the preferred value is -1.
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getAnother
public SequenceIterator getAnother() throws XPathException
Get another iterator to return the same nodes- Specified by:
getAnother
in interfaceSequenceIterator
- Returns:
- a SequenceIterator that iterates over the same items, positioned before the first item
- Throws:
XPathException
- if any error occurs
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getProperties
public int 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.GROUNDED
,SequenceIterator.LAST_POSITION_FINDER
, andSequenceIterator.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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