net.sf.saxon.sort

Class EqualityComparer

public class EqualityComparer extends 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
static EqualityComparerTHE_INSTANCE
Method Summary
intcompareAtomicValues(AtomicValue a, AtomicValue b)
Compare two AtomicValue objects according to the rules for their data type.
booleancomparesEqual(AtomicValue a, AtomicValue b)
Compare two AtomicValue objects for equality according to the rules for their data type.
ComparisonKeygetComparisonKey(AtomicValue a)
Get a comparison key for an object.
static EqualityComparergetInstance()
Get the singleton instance of this class
AtomicComparerprovideContext(XPathContext context)
Supply the dynamic context in case this is needed for the comparison

Field Detail

THE_INSTANCE

public static EqualityComparer THE_INSTANCE

Method Detail

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.

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 a0 if a>b

Throws: 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.

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: ClassCastException if the objects are not comparable

getComparisonKey

public ComparisonKey getComparisonKey(AtomicValue a)
Get a comparison key for an object. This must satisfy the rule that if two objects are equal, then their comparison keys are equal, and vice versa. There is no requirement that the comparison keys should reflect the ordering of the underlying objects.

getInstance

public static EqualityComparer getInstance()
Get the singleton instance of this class

Returns: the singleton instance of this class

provideContext

public AtomicComparer provideContext(XPathContext context)
Supply the dynamic context in case this is needed for the comparison

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