net.sf.saxon.value

Class StringValue

java.lang.Object

net.sf.saxon.om.AbstractItem

net.sf.saxon.value.AtomicValue

net.sf.saxon.value.StringValue

All Implemented Interfaces:

Iterable<AtomicValue>, PullEvent, AtomicSequence, GroundedValue, IdentityComparable, Item, Sequence, ConversionResult

Direct Known Subclasses:

AnyURIValue, UntypedAtomicValue

public class StringValue
extends AtomicValue

An atomic value of type xs:string. This class is also used for types derived from xs:string. Subclasses of StringValue are used for xs:untypedAtomic and xs:anyURI values.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	StringValue.CharacterIterator CharacterIterator is used to iterate over the characters in a string, returning them as integers representing the Unicode code-point.
class	StringValue.UnicodeCharacterIterator

Field Summary

Fields

Modifier and Type	Field and Description
static StringValue	EMPTY_STRING
static StringValue	FALSE
static StringValue	SINGLE_SPACE
static StringValue	TRUE
protected CharSequence	value

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

NaN_MATCH_KEY, typeLabel

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	StringValue() Protected constructor for use by subtypes
	StringValue(CharSequence value) Constructor.
	StringValue(CharSequence value, AtomicType typeLabel) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
String	asString() Returns the underlying string, with the side-effect of storing the string internally for future use, potentially reducing the cost if it is ever needed again
boolean	codepointEquals(StringValue other) Test whether this StringValue is equal to another under the rules of the codepoint collation
boolean	containsSurrogatePairs() Determine whether the string contains surrogate pairs
static CharSequence	contract(int[] codes, int used) Contract an array of integers containing Unicode codepoints into a Java string
AtomicValue	copyAsSubType(AtomicType typeLabel) Create a copy of this atomic value, with a different type label
static String	diagnosticDisplay(String s) Produce a diagnostic representation of the contents of the string
boolean	effectiveBooleanValue() Get the effective boolean value of a string
boolean	equals(Object other) Determine if two AtomicValues are equal, according to XPath rules.
static int[]	expand(CharSequence s) Expand a string containing surrogate pairs into an array of 32-bit characters
CharSequence	getPrimitiveStringValue() Get the string value as a CharSequence
BuiltInAtomicType	getPrimitiveType() Determine the primitive type of the value.
Comparable	getSchemaComparable() Get a Comparable value that implements the XML Schema comparison semantics for this value.
int	getStringLength() Get the length of this string, as defined in XPath.
static int	getStringLength(CharSequence s) Get the length of a string, as defined in XPath.
int	getStringLengthUpperBound() Get an upper bound on the length of the string in Unicode codepoints.
UnicodeString	getUnicodeString() Get a UnicodeString value representing the same characters as this string.
AtomicMatchKey	getXPathComparable(boolean ordered, StringCollator collator, int implicitTimezone) Get an object value that implements the XPath equality and ordering comparison semantics for this value.
int	hashCode()
boolean	isIdentical(AtomicValue v) Determine whether two atomic values are identical, as determined by XML Schema rules.
boolean	isKnownToContainNoSurrogates() Ask whether the string is known to contain no surrogate pairs.
boolean	isZeroLength() Determine whether the string is a zero-length string.
UnfailingIterator	iterateCharacters() Iterate over a string, returning a sequence of integers representing the Unicode code-point values
static StringValue	makeStringValue(CharSequence value) Factory method.
void	setContainsNoSurrogates() Assert that the string is known to contain no surrogate pairs
void	setStringValueCS(CharSequence value) Set the value of the item as a CharSequence.
String	toString() Get string value.

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

asAtomic, checkPermittedContents, getCanonicalLexicalRepresentation, getCardinality, getComponent, getItemType, getStringValue, getStringValueCS, head, identityHashCode, isIdentical, isNaN, itemAt, iterate, iterator, process, setTypeLabel

Methods inherited from class net.sf.saxon.om.AbstractItem

getLength, reduce, subsequence

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface net.sf.saxon.om.AtomicSequence

getLength

Methods inherited from interface net.sf.saxon.om.GroundedValue

reduce, subsequence

Field Detail

EMPTY_STRING

public static final StringValue EMPTY_STRING

SINGLE_SPACE

public static final StringValue SINGLE_SPACE

TRUE

public static final StringValue TRUE

FALSE

public static final StringValue FALSE

value

protected CharSequence value

Constructor Detail

StringValue

protected StringValue()

Protected constructor for use by subtypes

StringValue

public StringValue(CharSequence value)

Constructor. Note that although a StringValue may wrap any kind of CharSequence (usually a String, but it can also be, for example, a StringBuffer), the caller is responsible for ensuring that the value is immutable.

Parameters:

value - the String value. Null is taken as equivalent to "".

StringValue

public StringValue(CharSequence value,
           AtomicType typeLabel)

Constructor. Note that although a StringValue may wrap any kind of CharSequence (usually a String, but it can also be, for example, a StringBuffer), the caller is responsible for ensuring that the value is immutable.

Parameters:

value - the String value.

typeLabel - the type of the value to be created. The caller must ensure that this is a type derived from string and that the string is valid against this type.

Method Detail

setContainsNoSurrogates

public void setContainsNoSurrogates()

Assert that the string is known to contain no surrogate pairs

copyAsSubType

public AtomicValue copyAsSubType(AtomicType typeLabel)

Create a copy of this atomic value, with a different type label

Specified by:

copyAsSubType in class AtomicValue

Parameters:

typeLabel - the type label of the new copy. The caller is responsible for checking that the value actually conforms to this type.

Returns:

the copied value

getPrimitiveType

public BuiltInAtomicType getPrimitiveType()

Determine the primitive type of the value. This delivers the same answer as getItemType().getPrimitiveItemType(). The primitive types are the 19 primitive types of XML Schema, plus xs:integer, xs:dayTimeDuration and xs:yearMonthDuration, and xs:untypedAtomic. For external objects, the result is AnyAtomicType.

Specified by:

getPrimitiveType in class AtomicValue

Returns:

the primitive type

makeStringValue

public static StringValue makeStringValue(CharSequence value)

Factory method. Unlike the constructor, this avoids creating a new StringValue in the case of a zero-length string (and potentially other strings, in future)

Parameters:

value - the String value. Null is taken as equivalent to "".

Returns:

the corresponding StringValue

getPrimitiveStringValue

public final CharSequence getPrimitiveStringValue()

Get the string value as a CharSequence

Specified by:

getPrimitiveStringValue in class AtomicValue

Returns:

the value converted to a string according to the rules for the primitive type

setStringValueCS

public final void setStringValueCS(CharSequence value)

Set the value of the item as a CharSequence.

For system use only. In principle, a StringValue is immutable. However, in special circumstances, if it is newly constructed, the content can be changed to reflect the effect of the whiteSpace facet.

Parameters:

value - the value of the string

getStringLength

public int getStringLength()

Get the length of this string, as defined in XPath. This is not the same as the Java length, as a Unicode surrogate pair counts as a single character

Returns:

the length of the string in Unicode code points

getStringLengthUpperBound

public int getStringLengthUpperBound()

Get an upper bound on the length of the string in Unicode codepoints.

Returns:

a value N such that getStringLength <= N. In practice, if the string is held as UTF16 codepoints this will be the length in UTF16 codepoints; if it is held in Unicode codepoints, it will be the length in Unicode codepoints

getUnicodeString

public UnicodeString getUnicodeString()

Get a UnicodeString value representing the same characters as this string. This is a memo-function; the value is computed the first time it is needed, and is cached for subsequent reuse

Returns:

the corresponding UnicodeString

getStringLength

public static int getStringLength(CharSequence s)

Get the length of a string, as defined in XPath. This is not the same as the Java length, as a Unicode surrogate pair counts as a single character.

Parameters:

s - The string whose length is required

Returns:

the length of the string in Unicode code points

isZeroLength

public boolean isZeroLength()

Determine whether the string is a zero-length string. This may be more efficient than testing whether the length is equal to zero

Returns:

true if the string is zero length

containsSurrogatePairs

public boolean containsSurrogatePairs()

Determine whether the string contains surrogate pairs

Returns:

true if the string contains any non-BMP characters

isKnownToContainNoSurrogates

public boolean isKnownToContainNoSurrogates()

Ask whether the string is known to contain no surrogate pairs.

Returns:

true if it is known to contain no surrogates, false if the answer is not known

iterateCharacters

public UnfailingIterator iterateCharacters()

Iterate over a string, returning a sequence of integers representing the Unicode code-point values

Returns:

an iterator over the characters (Unicode code points) in the string

expand

public static int[] expand(CharSequence s)

Expand a string containing surrogate pairs into an array of 32-bit characters

Parameters:

s - the string to be expanded

Returns:

an array of integers representing the Unicode code points

contract

public static CharSequence contract(int[] codes,
                    int used)

Contract an array of integers containing Unicode codepoints into a Java string

Parameters:

codes - an array of integers representing the Unicode code points

used - the number of items in the array that are actually used

Returns:

the constructed string

getXPathComparable

public AtomicMatchKey getXPathComparable(boolean ordered,
                                StringCollator collator,
                                int implicitTimezone)

Get an object value that implements the XPath equality and ordering comparison semantics for this value. If the ordered parameter is set to true, the result will be a Comparable and will support a compareTo() method with the semantics of the XPath lt/gt operator, provided that the other operand is also obtained using the getXPathComparable() method. In all cases the result will support equals() and hashCode() methods that support the semantics of the XPath eq operator, again provided that the other operand is also obtained using the getXPathComparable() method. A context argument is supplied for use in cases where the comparison semantics are context-sensitive, for example where they depend on the implicit timezone or the default collation.

Specified by:

getXPathComparable in class AtomicValue

Parameters:

ordered - true if an ordered comparison is required. In this case the result is null if the type is unordered; in other cases the returned value will be a Comparable.

collator - Collation to be used for comparing strings

implicitTimezone - the XPath dynamic evaluation context, used in cases where the comparison is context sensitive

Returns:

an Object whose equals() and hashCode() methods implement the XPath comparison semantics with respect to this atomic value. If ordered is specified, the result will either be null if no ordering is defined, or will be a Comparable

equals

public boolean equals(Object other)

Determine if two AtomicValues are equal, according to XPath rules. (This method is not used for string comparisons, which are always under the control of a collation. If we get here, it's because there's a type error in the comparison.)

Specified by:

equals in class AtomicValue

Parameters:

other - the other value

Returns:

true if the other operand is an atomic value and the two values are equal as defined by the XPath eq operator

Throws:

ClassCastException - always

hashCode

public int hashCode()

Overrides:

hashCode in class Object

asString

public String asString()

Returns the underlying string, with the side-effect of storing the string internally for future use, potentially reducing the cost if it is ever needed again

Returns:

the value as a String

codepointEquals

public boolean codepointEquals(StringValue other)

Test whether this StringValue is equal to another under the rules of the codepoint collation

Parameters:

other - the value to be compared with this value

Returns:

true if the strings are equal on a codepoint-by-codepoint basis

effectiveBooleanValue

public boolean effectiveBooleanValue()

Get the effective boolean value of a string

Specified by:

effectiveBooleanValue in interface GroundedValue

Overrides:

effectiveBooleanValue in class AtomicValue

Returns:

true if the string has length greater than zero

toString

public String toString()

Description copied from class: AtomicValue

Get string value. In general toString() for an atomic value displays the value as it would be written in XPath: that is, as a literal if available, or as a call on a constructor function otherwise.

Overrides:

toString in class AtomicValue

getSchemaComparable

public Comparable getSchemaComparable()

Get a Comparable value that implements the XML Schema comparison semantics for this value. Returns null if the value is not comparable according to XML Schema rules. This implementation returns the underlying Java string, which works because strings will only be compared for equality, not for ordering, and the equality rules for strings in XML schema are the same as in Java.

Specified by:

getSchemaComparable in interface AtomicSequence

Specified by:

getSchemaComparable in class AtomicValue

Returns:

a Comparable that follows XML Schema comparison rules

isIdentical

public boolean isIdentical(AtomicValue v)

Determine whether two atomic values are identical, as determined by XML Schema rules. This is a stronger test than equality (even schema-equality); for example two dateTime values are not identical unless they are in the same timezone.

Note that even this check ignores the type annotation of the value. The integer 3 and the short 3 are considered identical, even though they are not fully interchangeable. "Identical" means the same point in the value space, regardless of type annotation.

NaN is identical to itself.

Overrides:

isIdentical in class AtomicValue

Parameters:

v - the other value to be compared with this one

Returns:

true if the two values are identical, false otherwise.

diagnosticDisplay

public static String diagnosticDisplay(String s)

Produce a diagnostic representation of the contents of the string

Parameters:

s - the string

Returns:

a string in which non-Ascii-printable characters are replaced by \ uXXXX escapes