net.sf.saxon.expr.sort

Class EqualityComparer

java.lang.Object

net.sf.saxon.expr.sort.EqualityComparer

All Implemented Interfaces:

AtomicComparer

public class EqualityComparer
extends java.lang.Object
implements AtomicComparer

A comparer for comparing two atomic values where (a) equals is defined, and is implemented using the Java equals() method, and (b) ordering is not defined, and results in a dynamic error.

Field Summary

Fields

Modifier and Type	Field and Description
static EqualityComparer	THE_INSTANCE

Method Summary

Modifier and Type	Method and Description
int	compareAtomicValues(AtomicValue a, AtomicValue b) Compare two AtomicValue objects according to the rules for their data type.
boolean	comparesEqual(AtomicValue a, AtomicValue b) Compare two AtomicValue objects for equality according to the rules for their data type.
StringCollator	getCollator() Get the collation used by this AtomicComparer if any
static EqualityComparer	getInstance() Get the singleton instance of this class
AtomicComparer	provideContext(XPathContext context) Supply the dynamic context in case this is needed for the comparison
java.lang.String	save() Create a string representation of this AtomicComparer that can be saved in a compiled package and used to reconstitute the AtomicComparer when the package is reloaded

Methods inherited from class java.lang.Object

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

Field Detail

THE_INSTANCE

public static EqualityComparer THE_INSTANCE

Method Detail

getInstance

public static EqualityComparer getInstance()

Get the singleton instance of this class

Returns:

the singleton instance of this class

getCollator

public StringCollator getCollator()

Description copied from interface: AtomicComparer

Get the collation used by this AtomicComparer if any

Specified by:

getCollator in interface AtomicComparer

Returns:

the collation used for comparing strings, or null if not applicable

provideContext

public AtomicComparer provideContext(XPathContext context)

Supply the dynamic context in case this is needed for the comparison

Specified by:

provideContext in interface AtomicComparer

Parameters:

context - the dynamic evaluation context

Returns:

either the original AtomicComparer, or a new AtomicComparer in which the context is known. The original AtomicComparer is not modified

compareAtomicValues

public int compareAtomicValues(AtomicValue a,
                               AtomicValue b)

Compare two AtomicValue objects according to the rules for their data type. UntypedAtomic values are compared as if they were strings; if different semantics are wanted, the conversion must be done by the caller.

Specified by:

compareAtomicValues in interface AtomicComparer

Parameters:

a - the first object to be compared. It is intended that this should be an instance of AtomicValue, though this restriction is not enforced. If it is a StringValue, the collator is used to compare the values, otherwise the value must implement the java.util.Comparable interface.

b - the second object to be compared. This must be comparable with the first object: for example, if one is a string, they must both be strings.

Returns:

<0 if a<b, 0 if a=b, >0 if a>b

Throws:

java.lang.ClassCastException - if the objects are not comparable

comparesEqual

public boolean comparesEqual(AtomicValue a,
                             AtomicValue b)

Compare two AtomicValue objects for equality according to the rules for their data type. UntypedAtomic values are compared by converting to the type of the other operand.

Specified by:

comparesEqual in interface AtomicComparer

Parameters:

a - the first object to be compared. This must be an AtomicValue and it must implement equals() with context-free XPath comparison semantics

b - the second object to be compared. This must be an AtomicValue and it must implement equals() with context-free XPath comparison semantics

Returns:

true if the values are equal, false if not

Throws:

java.lang.ClassCastException - if the objects are not comparable

save

public java.lang.String save()

Create a string representation of this AtomicComparer that can be saved in a compiled package and used to reconstitute the AtomicComparer when the package is reloaded

Specified by:

save in interface AtomicComparer

Returns:

a string representation of the AtomicComparer