Package net.sf.saxon.tree.iter

Class EmptyIterator

java.lang.Object
net.sf.saxon.tree.iter.EmptyIterator
All Implemented Interfaces:
Closeable, AutoCloseable, LastPositionFinder, AtomizedValueIterator, SequenceIterator, GroundedIterator, LookaheadIterator, ReversibleIterator
public class EmptyIterator extends Object implements SequenceIterator, ReversibleIterator, LastPositionFinder, GroundedIterator, LookaheadIterator, AtomizedValueIterator
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

      protected EmptyIterator()
      Protected constructor

  • 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)

    • nextAtomizedValue

      public AtomicSequence nextAtomizedValue()
      Deliver the atomic value that is next in the atomized result
      Specified by:
      nextAtomizedValue in interface AtomizedValueIterator
      Returns:
      the next atomic value

    • next

      public Item next()
      Get the next item.
      Specified by:
      next in interface SequenceIterator
      Returns:
      the next item. For the EmptyIterator this is always null.

    • supportsGetLength

      public boolean supportsGetLength()
      Description copied from interface: LastPositionFinder
      Ask 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
      Specified by:
      supportsGetLength in interface LastPositionFinder
      Returns:
      true if the LastPositionFinder.getLength() method can be called to determine the length of the underlying sequence.

    • getLength

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

    • getReverseIterator

      public EmptyIterator 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)

    • materialize

      public GroundedValue 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

    • getResidue

      public GroundedValue getResidue()
      Description copied from interface: GroundedIterator
      Return a GroundedValue containing all the remaining items in the sequence returned by this SequenceIterator, starting at the current position. This should be an "in-memory" value, not a Closure. This method does not change the state of the iterator (in particular, it does not consume the iterator).
      Specified by:
      getResidue in interface GroundedIterator
      Returns:
      the corresponding Value

    • supportsHasNext

      public boolean supportsHasNext()
      Description copied from interface: LookaheadIterator
      Ask 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)
      Specified by:
      supportsHasNext in interface LookaheadIterator
      Returns:
      true if the LookaheadIterator.hasNext() method is available

    • 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

    • isActuallyGrounded

      public boolean isActuallyGrounded()
      Description copied from interface: GroundedIterator
      Ask if the iterator is actually grounded. This method must be called before calling GroundedIterator.materialize() or GroundedIterator.getResidue(), because the iterator might be grounded under some conditions and not others (usually when it delegates to another iterator)
      Specified by:
      isActuallyGrounded in interface GroundedIterator
      Returns:
      true if this iterator is grounded

    • ofNodes

      public static AxisIterator ofNodes()
      Static method to get an empty AxisIterator
      Returns:
      an empty AxisIterator

    • ofAtomic

      public static AtomicIterator ofAtomic()
      Static method to get an empty AtomicIterator
      Returns:
      an empty AtomicIterator