- All Implemented Interfaces:
public class TailIterator extends java.lang.Object implements SequenceIterator, LastPositionFinder, LookaheadIteratorTailIterator iterates over a base sequence starting at an element other than the first. The base sequence is represented by an iterator which is consumed in the process
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description
close()Close the iterator.
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.
getLength()Get the last position (that is, the number of items in the sequence).
hasNext()Determine whether there are more items to come.
make(SequenceIterator base, int start)Static factory method.
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 static SequenceIterator make(SequenceIterator base, int start) throws XPathExceptionStatic factory method. Creates a TailIterator, unless the base Iterator is an ArrayIterator, in which case it optimizes by creating a new ArrayIterator directly over the underlying array. This optimization is important when doing recursion over a node-set using repeated calls of
base- An iteration of the items to be filtered. The state of this iterator after the operation is undefined - it may or may not be consumed
start- The position of the first item to be included (origin 1). If <= 1, the whole of the base sequence is returned
- an iterator over the items in the sequence from the start item to the end of the sequence. The returned iterator will not necessarily be an instance of this class.
XPathException- if a dynamic error occurs
public Item next()Get 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.
public boolean supportsHasNext()Description copied from interface:
LookaheadIteratorAsk whether the hasNext() method can be called. This method must be called before calling hasNext(), because some iterators implement this interface, but only support look-ahead under particular circumstances (this is usually because they delegate to another iterator)
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 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 void close()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.
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.
public 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. This may require the iterator to calculate the rest of the sequence eagerly. The method is called by a client if it anticipates that it might not read the iterator to completion, but it cannot guarantee that
SequenceIterator.close()will be called when no more items are needed.