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## net.sf.saxon.tree.iter
Class OneItemGoneIterator

    java.lang.Object
      net.sf.saxon.tree.iter.OneItemGoneIterator

All Implemented Interfaces:
  LastPositionFinder, SequenceIterator, GroundedIterator, LookaheadIterator

    public class OneItemGoneIterator

extends Object
implements SequenceIterator, LastPositionFinder, GroundedIterator, LookaheadIterator

This is an iterator over a sequence whose first item has already been read. On entry, the baseIterator must be positioned so the second item in the sequence is the next item to be returned; the first item in the sequence is available by calling current() on the baseIterator.

This avoids the cost of calling getAnother() to re-read the first item (which itself can be an expensive operation, for example if it involves calling a user function).

Field Summary

Fields inherited from interface net.sf.saxon.om.SequenceIterator
`GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD`

Constructor Summary
`OneItemGoneIterator(SequenceIterator baseIterator)` Create an iterator that delivers all the items that the base iterator delivers, even though the first item of the base iterator has already been read

Method Summary
`void` | `close()` Close the iterator.
`Item` | `current()` Get the current value in the sequence (the one returned by the most recent call on next()).
`SequenceIterator` | `getAnother()` Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.
`int` | `getLastPosition()` Get the last position (that is, the number of items in the sequence).
`int` | `getProperties()` Get properties of this iterator, as a bit-significant integer.
`boolean` | `hasNext()` Determine whether there are more items to come.
`GroundedValue` | `materialize()` Return a GroundedValue containing all the items in the sequence returned by this SequenceIterator.
`Item` | `next()` Get the next item in the sequence.
`int` | `position()` Get the current position.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### OneItemGoneIterator

    public OneItemGoneIterator(SequenceIterator baseIterator)

  Create an iterator that delivers all the items that the base iterator delivers, even though the first item of the base iterator has already been read

  Parameters:
    `baseIterator` - the base iterator, whose current position must be 1

Method Detail

### next

    public Item next()
              throws XPathException

  Get the next item in the sequence. This method changes the state of the iterator, in particular it affects the result of subsequent calls of position() and current().

  Specified by:
    `next` in interface `SequenceIterator`
  Returns:
    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.
  Throws:
    `XPathException` - if an error occurs retrieving the next item
  Since:
    8.4

### current

    public Item current()

  Get the current value in the sequence (the one returned by the most recent call on next()). This will be null before the first call of next(). This method does not change the state of the iterator.

  Specified by:
    `current` in interface `SequenceIterator`
  Returns:
    the current item, the one most recently returned by a call on next(). Returns null if next() has not been called, or if the end of the sequence has been reached.
  Since:
    8.4

### position

    public int position()

  Get the current position. This will usually be zero before the first call on next(), otherwise it will be the number of times that next() has been called. Once next() has returned null, the preferred action is for subsequent calls on position() to return -1, but not all existing implementations follow this practice. (In particular, the EmptyIterator is stateless, and always returns 0 as the value of position(), whether or not next() has been called.)

  This method does not change the state of the iterator.

  Specified by:
    `position` in interface `SequenceIterator`
  Returns:
    the current position, the position of the item returned by the most recent call of next(). This is 1 after next() has been successfully called once, 2 after it has been called twice, and so on. If next() has never been called, the method returns zero. If the end of the sequence has been reached, the value returned will always be <= 0; the preferred value is -1.
  Since:
    8.4

### close

    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.

  (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`
  Since:
    9.1

### getAnother

    public SequenceIterator getAnother()
                                throws XPathException

  Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.

  This method allows access to all the items in the sequence without disturbing the current position of the iterator. Internally, its main use is in evaluating the last() function.

  This method does not change the state of the iterator.

  Specified by:
    `getAnother` in interface `SequenceIterator`
  Returns:
    a SequenceIterator that iterates over the same items, positioned before the first item
  Throws:
    `XPathException` - if any error occurs
  Since:
    8.4

### 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.
  Since:
    8.6

### getLastPosition

    public int getLastPosition()
                        throws XPathException

  Get 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 result of getProperties() on the iterator includes the bit setting `SequenceIterator.LAST_POSITION_FINDER`

  Specified by:
    `getLastPosition` in interface `LastPositionFinder`
  Throws:
    `XPathException`

### materialize

    public GroundedValue materialize()
                              throws XPathException

  Return a GroundedValue 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
  Throws:
    `XPathException`

### 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.

  This method must not be called unless the result of getProperties() on the iterator includes the bit setting `SequenceIterator.LOOKAHEAD`

  Specified by:
    `hasNext` in interface `LookaheadIterator`
  Returns:
    true if there are more items in the sequence

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