Package net.sf.saxon.expr

## Class TailIterator

- java.lang.Object
- - net.sf.saxon.expr.TailIterator

- All Implemented Interfaces:
    `java.io.Closeable`, `java.lang.AutoCloseable`, `LastPositionFinder`, `SequenceIterator`, `LookaheadIterator`

      public class TailIterator
      extends java.lang.Object
      implements SequenceIterator, LastPositionFinder, LookaheadIterator

  TailIterator iterates over a base sequence starting at an element other than the first. The base sequence is represented by an iterator which is consumed in the process

- - ### Nested Class Summary

    - ### Nested classes/interfaces inherited from interface net.sf.saxon.om.SequenceIterator

      `SequenceIterator.Property`

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `void` | `close()` | Close the iterator.
    `int` | `getLength()` | Get the last position (that is, the number of items in the sequence).
    `java.util.EnumSet<SequenceIterator.Property>` | `getProperties()` | Get properties of this iterator, as a bit-significant integer.
    `boolean` | `hasNext()` | Determine whether there are more items to come.
    `static <T extends Item> SequenceIterator` | `make​(SequenceIterator base, int start)` | Static factory method.
    `Item` | `next()` | Get the next item in the sequence.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

    - ### Methods inherited from interface net.sf.saxon.om.SequenceIterator

      `forEachOrFail, materialize`

- - ### Method Detail

    - #### make

          public static <T extends Item> SequenceIterator make​(SequenceIterator base,
                                                               int start)
                                                        throws XPathException

      Static factory method. Creates a TailIterator, unless the base Iterator is an ArrayIterator, in which case it optimizes by creating a new ArrayIterator directly over the underlying array. This optimization is important when doing recursion over a node-set using repeated calls of `$nodes[position()>1]`
      Parameters:
        `base` - An iteration of the items to be filtered
        `start` - The position of the first item to be included (base 1). If <= 1, the whole of the base sequence is returned
      Returns:
        an iterator over the items in the sequence from the start item to the end of the sequence. The returned iterator will not necessarily be an instance of this class.
      Throws:
        `XPathException` - if a dynamic error occurs

    - #### next

          public Item next()
                    throws XPathException

      Description copied from interface: `SequenceIterator`
      Get the next item in the sequence. This method changes the state of the iterator.
      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

    - #### hasNext

          public boolean hasNext()

      Description copied from interface: `LookaheadIterator`
      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 property `SequenceIterator.Property.LOOKAHEAD`

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

    - #### getLength

          public int getLength()
                        throws XPathException

      Description copied from interface: `LastPositionFinder`
      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.Property.LAST_POSITION_FINDER`
      Specified by:
        `getLength` in interface `LastPositionFinder`
      Returns:
        the number of items in the sequence
      Throws:
        `XPathException` - if an error occurs evaluating the sequence in order to determine the number of items

    - #### 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.

      For example, the iterator returned by the unparsed-text-lines() function has a close() method that causes the underlying input stream to be closed, whether or not the file has been read to completion.

      Closing an iterator is important 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 `java.lang.AutoCloseable`
      Specified by:
        `close` in interface `java.io.Closeable`
      Specified by:
        `close` in interface `SequenceIterator`

    - #### getProperties

          public java.util.EnumSet<SequenceIterator.Property> 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.Property.GROUNDED`, `SequenceIterator.Property.LAST_POSITION_FINDER`, and `SequenceIterator.Property.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.