Package net.sf.saxon.expr

## Class CardinalityCheckingIterator

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

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

      public final class CardinalityCheckingIterator
      extends java.lang.Object
      implements SequenceIterator

  CardinalityCheckingIterator returns the items in an underlying sequence unchanged, but checks that the number of items conforms to the required cardinality. Because cardinality checks are required to take place even if the consumer of the sequence does not require all the items, we read the first two items at initialization time. This is sufficient to perform the checks; after that we can simply return the items from the base sequence.

- - ### Nested Class Summary

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

      `SequenceIterator.Property`

  - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `CardinalityCheckingIterator​(SequenceIterator base, int requiredCardinality, RoleDiagnostic role, Location locator)` | Construct an CardinalityCheckingIterator that will return the same items as the base sequence, checking how many there are

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `void` | `close()` | Close the iterator.
    `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, getProperties, materialize`

- - ### Constructor Detail

    - #### CardinalityCheckingIterator

          public CardinalityCheckingIterator​(SequenceIterator base,
                                             int requiredCardinality,
                                             RoleDiagnostic role,
                                             Location locator)
                                      throws XPathException

      Construct an CardinalityCheckingIterator that will return the same items as the base sequence, checking how many there are
      Parameters:
        `base` - the base iterator
        `requiredCardinality` - the required Cardinality
        `role` - information for use if a failure occurs
        `locator` - the location in the source stylesheet or query
      Throws:
        `XPathException` - if a failure is detected

  - ### Method Detail

    - #### 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

    - #### 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`