net.sf.saxon.om

Class EmptyAtomicSequence

java.lang.Object

net.sf.saxon.om.EmptyAtomicSequence

All Implemented Interfaces:

java.lang.Iterable<AtomicValue>, AtomicSequence, GroundedValue, Sequence

public class EmptyAtomicSequence
extends java.lang.Object
implements AtomicSequence

An implementation of AtomicSequence that contains no items.

Constructor Summary

Constructors

Constructor and Description
EmptyAtomicSequence()

Method Summary

Modifier and Type	Method and Description
boolean	effectiveBooleanValue() Get the effective boolean value of this sequence
java.lang.CharSequence	getCanonicalLexicalRepresentation() Get the canonical lexical representation as defined in XML Schema.
static EmptyAtomicSequence	getInstance()
int	getLength() Get the length of the sequence
java.lang.Comparable	getSchemaComparable() Get a Comparable value that implements the XML Schema ordering comparison semantics for this value.
java.lang.String	getStringValue() Get a string representation of the sequence.
java.lang.CharSequence	getStringValueCS() Get a string representation of the sequence.
AtomicValue	head() Get the first item in the sequence
AtomicValue	itemAt(int n) Get the Nth item in the sequence, zero-based
AtomicIterator	iterate() Make an iterator over the items in the sequence
java.util.Iterator<AtomicValue>	iterator() Return a Java iterator over the atomic 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

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Detail

EmptyAtomicSequence

public EmptyAtomicSequence()

Method Detail

getInstance

public static EmptyAtomicSequence getInstance()

head

public AtomicValue head()

Description copied from interface: AtomicSequence

Get the first item in the sequence

Specified by:

head in interface AtomicSequence

Specified by:

head in interface GroundedValue

Specified by:

head in interface Sequence

Returns:

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

iterate

public AtomicIterator iterate()

Description copied from interface: AtomicSequence

Make an iterator over the items in the sequence

Specified by:

iterate in interface AtomicSequence

Specified by:

iterate in interface GroundedValue

Specified by:

iterate in interface Sequence

Returns:

an interator over the items in the sequence

itemAt

public AtomicValue itemAt(int n)

Description copied from interface: AtomicSequence

Get the Nth item in the sequence, zero-based

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 Nth item in the sequence, or null if the index is out of range

getLength

public int getLength()

Description copied from interface: AtomicSequence

Get the length of the sequence

Specified by:

getLength in interface AtomicSequence

Specified by:

getLength in interface GroundedValue

Returns:

the number of items in the sequence

getCanonicalLexicalRepresentation

public java.lang.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 java.lang.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 java.lang.CharSequence getStringValueCS()

Description copied from interface: AtomicSequence

Get a string representation of the sequence. The is the space-separated concatenation of the result of casting each of the items in the sequence to xs:string

Specified by:

getStringValueCS in interface AtomicSequence

Specified by:

getStringValueCS in interface GroundedValue

Returns:

a whitespace-separated concatenation of the string values of the items making up the sequence, as a CharSequence.

getStringValue

public java.lang.String getStringValue()

Description copied from interface: AtomicSequence

Get a string representation of the sequence. The is the space-separated concatenation of the result of casting each of the items in the sequence to xs:string

Specified by:

getStringValue in interface AtomicSequence

Specified by:

getStringValue in interface GroundedValue

Returns:

a whitespace-separated concatenation of the string values of the items making up the sequence, as a String.

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

iterator

public java.util.Iterator<AtomicValue> iterator()

Return a Java iterator over the atomic sequence.

Specified by:

iterator in interface java.lang.Iterable<AtomicValue>

Returns:

an Iterator.