Package net.sf.saxon.tree.iter

Class EmptyIterator<T extends Item<?>>

java.lang.Object
net.sf.saxon.tree.iter.EmptyIterator<T>
All Implemented Interfaces:
Closeable, AutoCloseable, LastPositionFinder, AtomizedValueIterator<T>, SequenceIterator<T>, GroundedIterator<T>, LookaheadIterator<T>, ReversibleIterator<T>, UnfailingIterator<T>
Direct Known Subclasses:
EmptyIterator.OfAtomic, EmptyIterator.OfNodes
public class EmptyIterator<T extends Item<?>> extends Object implements SequenceIterator<T>, ReversibleIterator<T>, LastPositionFinder, GroundedIterator<T>, LookaheadIterator<T>, UnfailingIterator<T>, AtomizedValueIterator<T>
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)

    • emptyIterator

      public static <T extends Item<?>> EmptyIterator<T> emptyIterator()

    • nextAtomizedValue

      public AtomicSequence nextAtomizedValue()
      Deliver the atomic value that is next in the atomized result
      Specified by:
      nextAtomizedValue in interface AtomizedValueIterator<T extends Item<?>>
      Returns:
      the next atomic value

    • next

      public T next()
      Get the next item.
      Specified by:
      next in interface SequenceIterator<T extends Item<?>>
      Specified by:
      next in interface UnfailingIterator<T extends Item<?>>
      Returns:
      the next item. For the EmptyIterator this is always null.

    • 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<T> getReverseIterator()
      Get another iterator over the same items, in reverse order.
      Specified by:
      getReverseIterator in interface ReversibleIterator<T extends Item<?>>
      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<T extends Item<?>>
      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 GroundedValue<T> 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<T extends Item<?>>
      Specified by:
      materialize in interface SequenceIterator<T extends Item<?>>
      Returns:
      the corresponding Value

    • getResidue

      public GroundedValue<T> 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<T extends Item<?>>
      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<T extends Item<?>>
      Returns:
      true if there are more nodes