Class EmptyIterator

java.lang.Object
net.sf.saxon.om.EmptyIterator
All Implemented Interfaces:
LastPositionFinder, ReversibleIterator, AxisIterator, GroundedIterator, LookaheadIterator, SequenceIterator
public class EmptyIterator extends Object implements AxisIterator, ReversibleIterator, LastPositionFinder, GroundedIterator, LookaheadIterator
EmptyIterator: an iterator over an empty sequence. Since such an iterator has no state, only one instance is required; therefore a singleton instance is available via the static getInstance() method.

  • Constructor Details

    • EmptyIterator

      public EmptyIterator()

  • Method Details

    • getInstance

      public static EmptyIterator getInstance()
      Get an EmptyIterator, an iterator over an empty sequence.
      Returns:
      an EmptyIterator (in practice, this always returns the same one)

    • next

      public Item next()
      Get the next item. This method should not be called unless hasNext() returns true.
      Specified by:
      next in interface AxisIterator
      Specified by:
      next in interface SequenceIterator
      Returns:
      the next item. For the EmptyIterator this is always null.

    • current

      public Item current()
      Get the current item, that is, the item returned by the most recent call of next().
      Specified by:
      current in interface AxisIterator
      Specified by:
      current in interface SequenceIterator
      Returns:
      the current item. For the EmptyIterator this is always null.

    • position

      public int position()
      Get the position of the current item.
      Specified by:
      position in interface AxisIterator
      Specified by:
      position in interface SequenceIterator
      Returns:
      the position of the current item. For the EmptyIterator this is always zero (whether or not the next() method has been called).

    • getLastPosition

      public int getLastPosition()
      Get the position of the last item in the sequence.
      Specified by:
      getLastPosition in interface LastPositionFinder
      Returns:
      the position of the last item in the sequence, always zero in this implementation

    • getAnother

      public SequenceIterator getAnother()
      Get another iterator over the same items, positioned at the start.
      Specified by:
      getAnother in interface AxisIterator
      Specified by:
      getAnother in interface SequenceIterator
      Returns:
      another iterator over an empty sequence (in practice, it returns the same iterator each time)

    • getReverseIterator

      public SequenceIterator getReverseIterator()
      Get another iterator over the same items, in reverse order.
      Specified by:
      getReverseIterator in interface ReversibleIterator
      Returns:
      a reverse iterator over an empty sequence (in practice, it returns the same iterator each time)

    • getProperties

      public int getProperties()
      Get properties of this iterator, as a bit-significant integer.
      Specified by:
      getProperties in interface SequenceIterator
      Returns:
      the properties of this iterator. This will be some combination of properties such as SequenceIterator.GROUNDED, SequenceIterator.LAST_POSITION_FINDER, and SequenceIterator.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.

    • materialize

      public Value materialize()
      Return a Value containing all the items in the sequence returned by this SequenceIterator. This should be an "in-memory" value, not a Closure.
      Specified by:
      materialize in interface GroundedIterator
      Returns:
      the corresponding Value

    • hasNext

      public boolean hasNext()
      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.
      Specified by:
      hasNext in interface LookaheadIterator
      Returns:
      true if there are more nodes