net.sf.saxon.value

Class EmptySequence

public final class EmptySequence extends Value

An EmptySequence object represents a sequence containing no members.

Method Summary
void	display(int level, NamePool pool, PrintStream out) Diagnostic print of expression structure
boolean	effectiveBooleanValue(XPathContext context) Get the effective boolean value - always false
boolean	equals(Object other) Is this expression the same as another expression?
int	getCardinality() Determine the static cardinality
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
static EmptySequence	getInstance() Get the implicit instance of this class
ItemType	getItemType(TypeHierarchy th) Determine the item type
int	getLength() Get the length of the sequence
int	getSpecialProperties() Get the static properties of this expression (other than its type).
int	hashCode()
SequenceIterator	iterate(XPathContext context) Return an iteration over the sequence

Method Detail

display

public void display(int level, NamePool pool, PrintStream out)

Diagnostic print of expression structure

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)

Get the effective boolean value - always false

equals

public boolean equals(Object other)

Is this expression the same as another expression?

Throws: ClassCastException if the values are not comparable

getCardinality

public int getCardinality()

Determine the static cardinality

getImplementationMethod

public int getImplementationMethod()

An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is prefered.

getInstance

public static EmptySequence getInstance()

Get the implicit instance of this class

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the item type

Parameters: th

getLength

public final int getLength()

Get the length of the sequence

Returns: always 0 for an empty sequence

Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.

hashCode

public int hashCode()

iterate

public SequenceIterator iterate(XPathContext context)

Return an iteration over the sequence