Class SingletonItem<T extends Item>

java.lang.Object
net.sf.saxon.value.Value<T>
net.sf.saxon.value.SingletonItem<T>
All Implemented Interfaces:
GroundedValue<T>, ValueRepresentation<T>

public class SingletonItem<T extends Item> extends Value<T> implements GroundedValue<T>
A value that is a sequence containing zero or one items. Used only for items that are not atomic values (that is, nodes, and function items)
  • Field Details

    • item

      protected T extends Item item
  • Constructor Details

    • SingletonItem

      public SingletonItem(T item)
      Create a node-set containing zero or one nodes
      Parameters:
      item - The node or function-item to be contained in the node-set, or null if the sequence is to be empty
  • Method Details

    • asItem

      public T asItem()
      Return the value in the form of an Item
      Overrides:
      asItem in class Value<T extends Item>
      Returns:
      the value in the form of an Item
    • process

      public void process(XPathContext context) throws XPathException
      Process the instruction, without returning any tail calls
      Overrides:
      process in class Value<T extends Item>
      Parameters:
      context - The dynamic context, giving access to the current node, the current variables, etc.
      Throws:
      XPathException - if an error occurs (for example if the value is a closure that needs to be evaluated)
    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Determine the data type of the items in the expression. This method determines the most precise type that it can, because it is called when testing that the node conforms to a required type.
      Overrides:
      getItemType in class Value<T extends Item>
      Parameters:
      th - the type hierarchy cache
      Returns:
      the most precise possible type of the node.
    • getCardinality

      public int getCardinality()
      Determine the static cardinality
      Overrides:
      getCardinality in class Value<T extends Item>
      Returns:
      the cardinality
    • getLength

      public int getLength()
      Get the length of the sequence
      Specified by:
      getLength in interface GroundedValue<T extends Item>
      Overrides:
      getLength in class Value<T extends Item>
      Returns:
      the number of items in the sequence
    • itemAt

      public T itemAt(int n)
      Get the n'th item in the sequence (starting from 0). This is defined for all SequenceValues, but its real benefits come for a SequenceValue stored extensionally (or for a MemoClosure, once all the values have been read)
      Specified by:
      itemAt in interface GroundedValue<T extends Item>
      Overrides:
      itemAt in class Value<T extends Item>
      Parameters:
      n - position of the required item, counting from zero.
      Returns:
      the n'th item in the sequence, where the first item in the sequence is numbered zero. If n is negative or >= the length of the sequence, returns null.
    • subsequence

      public GroundedValue<T> subsequence(int start, int length)
      Get a subsequence of the value
      Specified by:
      subsequence in interface GroundedValue<T extends Item>
      Parameters:
      start - the index of the first item to be included in the result, counting from zero. A negative value is taken as zero. If the value is beyond the end of the sequence, an empty sequence is returned
      length - the number of items to be included in the result. Specify Integer.MAX_VALUE to get the subsequence up to the end of the base sequence. If the value is negative, an empty sequence is returned. If the value goes off the end of the sequence, the result returns items up to the end of the sequence
      Returns:
      the required subsequence. If min is
    • iterate

      public SequenceIterator<T> iterate()
      Return an enumeration of this nodeset value.
      Specified by:
      iterate in class Value<T extends Item>
      Returns:
      an iterator over the sequence of items
    • effectiveBooleanValue

      public boolean effectiveBooleanValue()
      Get the effective boolean value
      Overrides:
      effectiveBooleanValue in class Value<T extends Item>
      Returns:
      the effective boolean value
    • getStringValue

      public String getStringValue()
      Convert the value to a string, using the serialization rules. For atomic values this is the same as a cast; for sequence values it gives a space-separated list. For QNames and NOTATIONS, or lists containing them, it fails.
      Specified by:
      getStringValue in interface ValueRepresentation<T extends Item>
      Overrides:
      getStringValue in class Value<T extends Item>
      Returns:
      the result of converting the value to a string