Class EmptyIterator<T extends Item>

    • Constructor Detail

      • EmptyIterator

        protected EmptyIterator()
        Protected constructor
    • Method Detail

      • 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)
      • current

        public T current()
        Get the current item, that is, the item returned by the most recent call of next().
        Specified by:
        current in interface SequenceIterator<T extends Item>
        Specified by:
        current in interface UnfailingIterator<T extends Item>
        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 SequenceIterator<T extends Item>
        Specified by:
        position in interface UnfailingIterator<T extends Item>
        Returns:
        the position of the current item. For the EmptyIterator this is always zero (whether or not the next() method has been called).
      • getLength

        public int getLength()
        Get the position of the last item in the sequence.
        Specified by:
        getLength in interface LastPositionFinder<T extends Item>
        Returns:
        the position of the last item in the sequence, always zero in this implementation
      • close

        public void close()
        Description copied from interface: SequenceIterator
        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.

        (Currently, closing an iterator is important only 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.)

        Specified by:
        close in interface SequenceIterator<T extends Item>
      • atomize

        public Value atomize()
        Return the atomized value of the current node.
        Returns:
        the atomized value.
        Throws:
        java.lang.NullPointerException - always, because there is no current node
      • getStringValue

        public java.lang.CharSequence getStringValue()
        Return the string value of the current node.
        Returns:
        the string value, as an instance of CharSequence.
        Throws:
        java.lang.NullPointerException - if there is no current node
      • 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)
      • 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<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