Package net.sf.saxon.value

Class EmptySequence

java.lang.Object
net.sf.saxon.value.Value
net.sf.saxon.value.EmptySequence
All Implemented Interfaces:
Serializable, SequenceIterable, GroundedValue, ValueRepresentation
public final class EmptySequence extends Value implements GroundedValue
An EmptySequence object represents a sequence containing no members.
See Also:

  • Method Details

    • getInstance

      public static EmptySequence getInstance()
      Get the implicit instance of this class

    • iterate

      public SequenceIterator iterate()
      Return an iteration over the sequence
      Specified by:
      iterate in class Value
      Returns:
      an iterator over the sequence of items

    • asItem

      public Item asItem()
      Return the value in the form of an Item
      Overrides:
      asItem in class Value
      Returns:
      the value in the form of an Item

    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Determine the item type
      Overrides:
      getItemType in class Value
      Parameters:
      th - the type hierarchy cache
      Returns:
      for the default implementation: AnyItemType (not known)

    • getCardinality

      public int getCardinality()
      Determine the static cardinality
      Overrides:
      getCardinality in class Value
      Returns:
      the cardinality

    • getLength

      public final int getLength()
      Get the length of the sequence
      Overrides:
      getLength in class Value
      Returns:
      always 0 for an empty sequence

    • equals

      public boolean equals(Object other)
      Is this expression the same as another expression?
      Overrides:
      equals in class Value
      Throws:
      ClassCastException - if the values are not comparable

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • effectiveBooleanValue

      public boolean effectiveBooleanValue()
      Get the effective boolean value - always false
      Overrides:
      effectiveBooleanValue in class Value
      Returns:
      the effective boolean value

    • itemAt

      public Item itemAt(int n)
      Get the n'th item in the sequence (starting from 0). This is defined for all Values, but its real benefits come for a sequence Value stored extensionally (or for a MemoClosure, once all the values have been read)
      Specified by:
      itemAt in interface GroundedValue
      Overrides:
      itemAt in class Value
      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 subsequence(int min, int length)
      Get a subsequence of the value
      Specified by:
      subsequence in interface GroundedValue
      Parameters:
      min - 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