net.sf.saxon.om

Class EmptyAtomicSequence

java.lang.Object

net.sf.saxon.om.EmptyAtomicSequence

All Implemented Interfaces:

AtomicSequence, GroundedValue, Sequence

public class EmptyAtomicSequence
extends Object
implements AtomicSequence

An implementation of AtomicSequence that contains no items.

Constructor Summary

Constructors

Constructor and Description
EmptyAtomicSequence()

Method Summary

Methods

Modifier and Type	Method and Description
boolean	effectiveBooleanValue() Get the effective boolean value of this sequence
CharSequence	getCanonicalLexicalRepresentation() Get the canonical lexical representation as defined in XML Schema.
static EmptyAtomicSequence	getInstance()
int	getLength() Get the size of the value (the number of items)
Comparable	getSchemaComparable() Get a Comparable value that implements the XML Schema ordering comparison semantics for this value.
String	getStringValue() Get the string value of this sequence.
CharSequence	getStringValueCS() Get the string value of this sequence.
AtomicValue	head() Get the first item in the sequence.
AtomicValue	itemAt(int n) Get the n'th item in the value, counting from 0
SequenceIterator<? extends AtomicValue>	iterate() Get an iterator performance characteristics, though all should exhibit the same behaviour.over all the items in the sequence
GroundedValue	reduce() Reduce the sequence to its simplest form.
GroundedValue	subsequence(int start, int length) Get a subsequence of the value

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

EmptyAtomicSequence

public EmptyAtomicSequence()

Method Detail

getInstance

public static EmptyAtomicSequence getInstance()

head

public AtomicValue head()

Description copied from interface: Sequence

Get the first item in the sequence.

Specified by:

head in interface AtomicSequence

Specified by:

head in interface Sequence

Returns:

the first item in the sequence if there is one, or null if the sequence is empty

iterate

public SequenceIterator<? extends AtomicValue> iterate()

Description copied from interface: Sequence

Get an iterator performance characteristics, though all should exhibit the same behaviour.over all the items in the sequence

Specified by:

iterate in interface AtomicSequence

Specified by:

iterate in interface Sequence

Returns:

an iterator over all the items

itemAt

public AtomicValue itemAt(int n)

Description copied from interface: GroundedValue

Get the n'th item in the value, counting from 0

Specified by:

itemAt in interface AtomicSequence

Specified by:

itemAt in interface GroundedValue

Parameters:

n - the index of the required item, with 0 representing the first item in the sequence

Returns:

the n'th item if it exists, or null otherwise

getLength

public int getLength()

Description copied from interface: GroundedValue

Get the size of the value (the number of items)

Specified by:

getLength in interface AtomicSequence

Specified by:

getLength in interface GroundedValue

Returns:

the number of items in the sequence

getCanonicalLexicalRepresentation

public CharSequence getCanonicalLexicalRepresentation()

Get the canonical lexical representation as defined in XML Schema. This is not always the same as the result of casting to a string according to the XPath rules.

Specified by:

getCanonicalLexicalRepresentation in interface AtomicSequence

Returns:

the canonical lexical representation if defined in XML Schema; otherwise, the result of casting to string according to the XPath 2.0 rules

getSchemaComparable

public Comparable getSchemaComparable()

Get a Comparable value that implements the XML Schema ordering comparison semantics for this value. The default implementation is written to compare sequences of atomic values. This method is overridden for AtomicValue and its subclasses.

In the case of data types that are partially ordered, the returned Comparable extends the standard semantics of the compareTo() method by returning the value SequenceTool.INDETERMINATE_ORDERING when there is no defined order relationship between two given values.

Specified by:

getSchemaComparable in interface AtomicSequence

Returns:

a Comparable that follows XML Schema comparison rules

getStringValueCS

public CharSequence getStringValueCS()

Description copied from interface: GroundedValue

Get the string value of this sequence. The string value of an item is the result of applying the string() function. The string value of a sequence is the space-separated result of applying the string-join() function using a single space as the separator

Specified by:

getStringValueCS in interface AtomicSequence

Specified by:

getStringValueCS in interface GroundedValue

Returns:

the string value of the sequence.

getStringValue

public String getStringValue()

Description copied from interface: GroundedValue

Get the string value of this sequence. The string value of an item is the result of applying the string() function. The string value of a sequence is the space-separated result of applying the string-join() function using a single space as the separator

Specified by:

getStringValue in interface AtomicSequence

Specified by:

getStringValue in interface GroundedValue

Returns:

the string value of the sequence.

subsequence

public GroundedValue subsequence(int start,
                        int length)

Get a subsequence of the value

Specified by:

subsequence in interface GroundedValue

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

effectiveBooleanValue

public boolean effectiveBooleanValue()
                              throws XPathException

Description copied from interface: GroundedValue

Get the effective boolean value of this sequence

Specified by:

effectiveBooleanValue in interface GroundedValue

Returns:

the effective boolean value

Throws:

XPathException - if the sequence has no effective boolean value (for example a sequence of two integers)

reduce

public GroundedValue reduce()

Reduce the sequence to its simplest form. If the value is an empty sequence, the result will be EmptySequence.getInstance(). If the value is a single atomic value, the result will be an instance of AtomicValue. If the value is a single item of any other kind, the result will be an instance of SingletonItem. Otherwise, the result will typically be unchanged.

Specified by:

reduce in interface GroundedValue

Returns:

the simplified sequence