Class EmptySequence<T extends Item>

java.lang.Object
net.sf.saxon.value.Value<T>
net.sf.saxon.value.EmptySequence<T>
All Implemented Interfaces:
GroundedValue<T>, ValueRepresentation<T>
public final class EmptySequence<T extends Item> extends Value<T> implements GroundedValue<T>
An EmptySequence object represents a sequence containing no members.

  • Method Details

    • getInstance

      public static <T extends Item> EmptySequence<T> getInstance()
      Get the implicit instance of this class
      Returns:
      the singular instances of this class: an empty sequence

    • iterate

      public SequenceIterator<T> iterate()
      Return an iteration over the sequence
      Specified by:
      iterate in class Value<T extends Item>
      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<T extends Item>
      Returns:
      the value in the form of an Item

    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Determine the item type
      Overrides:
      getItemType in class Value<T extends Item>
      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<T extends Item>
      Returns:
      the cardinality

    • getLength

      public final 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:
      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<T extends Item>
      Throws:
      ClassCastException - if the values are not comparable

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Value<T extends Item>

    • effectiveBooleanValue

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

    • itemAt

      public T 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<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 min, int length)
      Get a subsequence of the value
      Specified by:
      subsequence in interface GroundedValue<T extends Item>
      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

    • toString

      public String toString()
      Returns a string representation of the object.
      Overrides:
      toString in class Object