net.sf.saxon.value

Class EmptySequence

Implemented Interfaces:
GroundedValue, Serializable, SequenceIterable, ValueRepresentation

public final class EmptySequence
extends Value
implements GroundedValue

An EmptySequence object represents a sequence containing no members.

Field Summary

Fields inherited from class net.sf.saxon.value.Value

EMPTY_CLASS_ARRAY, INDETERMINATE_ORDERING

Fields inherited from interface net.sf.saxon.om.ValueRepresentation

EMPTY_VALUE_ARRAY

Method Summary

Item
asItem()
Return the value in the form of an Item
boolean
effectiveBooleanValue()
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
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
hashCode()
Item
itemAt(int n)
Get the n'th item in the sequence (starting from 0).
SequenceIterator
iterate()
Return an iteration over the sequence
GroundedValue
subsequence(int min, int length)
Get a subsequence of the value

Methods inherited from class net.sf.saxon.value.Value

asItem, asItem, asIterator, asValue, checkPermittedContents, convertJavaObjectToXPath, convertToJava, convertToJava, effectiveBooleanValue, equals, fromItem, getCanonicalLexicalRepresentation, getCardinality, getItemType, getIterator, getLength, getSchemaComparable, getStringValue, getStringValueCS, itemAt, iterate, iterate, makeQNameValue, process, reduce, stringToNumber, toString

Method Details

asItem

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

effectiveBooleanValue

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

equals

public boolean equals(Object other)
Is this expression the same as another expression?
Overrides:
equals in interface Value

getCardinality

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

getInstance

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

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the item type
Overrides:
getItemType in interface Value
Parameters:
th - the type hierarchy cache

getLength

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

hashCode

public int hashCode()

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 interface 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.

iterate

public SequenceIterator iterate()
Return an iteration over the sequence
Overrides:
iterate in interface Value

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