Interface SequenceIterator

    • Method Summary

      All Methods Instance Methods Abstract Methods Default Methods 
      Modifier and Type Method Description
      default void close()
      Close the iterator.
      default void discharge()
      Calling this method instructs the iterator to release any resources it holds, while still remaining able to deliver the remaining items in the sequence.
      Item next()
      Get the next item in the sequence.
    • Method Detail

      • next

        Item next()
        Get the next item in the sequence. This method changes the state of the iterator.
        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:
        UncheckedXPathException - if an error occurs retrieving the next item
        Since:
        8.4. Changed in 11 so it no longer throws a checked exception; instead, any error that occurs is thrown as an unchecked exception.
      • close

        default 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.

        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.

        Closing an iterator is not necessary if the iterator is read to completion: if a call on next() returns null, the iterator will be closed automatically. An explicit call on close() is needed only when iteration is abandoned prematurely.

        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Since:
        9.1. Default implementation added in 9.9.
      • discharge

        default void discharge()
        Calling this method instructs the iterator to release any resources it holds, while still remaining able to deliver the remaining items in the sequence. This may require the iterator to calculate the rest of the sequence eagerly. The method is called by a client if it anticipates that it might not read the iterator to completion, but it cannot guarantee that close() will be called when no more items are needed.
        Since:
        11.1