- All Implemented Interfaces:
public class GroupAdjacentIterator extends java.lang.Object implements GroupIterator, LastPositionFinder, LookaheadIteratorA GroupAdjacentIterator iterates over a sequence of groups defined by xsl:for-each-group group-adjacent="x". The groups are returned in order of first appearance.
Each step of this iterator advances to the first item of the next group, leaving the members of that group in a saved list.
All Methods Instance Methods Concrete Methods Modifier and Type Method Description
close()Close the iterator.
currentGroup()Get a sequence containing the members of the current group, in population order.
getCurrentGroupingKey()Get the grouping key of the current group
getLength()Get the last position (that is, the number of items in the sequence).
getSnapShot(XPathContext context)Get a pseudo-iterator which represents a snapshot of this sequence at the current position
hasNext()Determine whether there are more items to come.
next()Get the next item in the sequence.
supportsGetLength()Ask whether this iterator supports use of the
supportsHasNext()Ask whether the hasNext() method can be called.
public boolean supportsGetLength()Description copied from interface:
LastPositionFinderAsk whether this iterator supports use of the
LastPositionFinder.getLength()method. This method should always be called before calling
LastPositionFinder.getLength(), because an iterator that implements this interface may support use of
LastPositionFinder.getLength()in some situations and not in others
public int getLength()Description copied from interface:
LastPositionFinderGet 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
LastPositionFinder.supportsGetLength()has been called and has returned true.
public AtomicSequence getCurrentGroupingKey()Get the grouping key of the current group
public GroundedValue currentGroup() throws XPathExceptionGet a sequence containing the members of the current group, in population order. This may be a MemoSequence rather than a grounded value
public boolean supportsHasNext()Description copied from interface:
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
public Item next()Description copied from interface:
SequenceIteratorGet the next item in the sequence. This method changes the state of the iterator.
- Specified by:
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.
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.
It is not possible to guarantee that an iterator that is not read to completion or will be closed. For example, if a lazy-evaluated variable
$varis passed to a user-written function, the function may access
$varonly; we have no way of knowing whether further items will be read. For this reason, any
SequenceIteratorthat holds resources which need to be closed should use the
Cleaner, and resources held by a
SequenceIteratorshould be registered with the
Cleaner; if the
SequenceIteratoris then garbage-collected without being closed, the
Cleanerwill ensure that the underlying resources are closed. (An example of a
SequenceIteratorthat uses this mechanism is the