net.sf.saxon.sort
Class GenericAtomicComparer

java.lang.Object
  net.sf.saxon.sort.GenericAtomicComparer

All Implemented Interfaces:

Serializable, AtomicComparer

public class GenericAtomicComparer
extends Object
implements AtomicComparer, Serializable

An AtomicComparer used for comparing atomic values of arbitrary item types. It encapsulates a Collator that is used when the values to be compared are strings. It also supports a separate method for testing equality of items, which can be used for data types that are not ordered.

Author:

Michael H. Kay

See Also:

Serialized Form

Constructor Summary

GenericAtomicComparer(StringCollator collator, Configuration config)

GenericAtomicComparer(StringCollator collator, XPathContext conversion)
Create an GenericAtomicComparer

Method Summary

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.
ComparisonKey	getComparisonKey(AtomicValue a) Get a comparison key for an object.
StringCollator	getStringCollator() Get the underlying string collator
static AtomicComparer	makeAtomicComparer(BuiltInAtomicType type0, BuiltInAtomicType type1, StringCollator collator, Configuration config) Factory method to make a GenericAtomicComparer for values of known types

Methods inherited from class java.lang.Object

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

Constructor Detail

GenericAtomicComparer

public GenericAtomicComparer(StringCollator collator,
                             XPathContext conversion)

Create an GenericAtomicComparer

Parameters:

collator - the collation to be used

conversion - a context, used when converting untyped atomic values to the target type.

GenericAtomicComparer

public GenericAtomicComparer(StringCollator collator,
                             Configuration config)

Method Detail

makeAtomicComparer

public static AtomicComparer makeAtomicComparer(BuiltInAtomicType type0,
                                                BuiltInAtomicType type1,
                                                StringCollator collator,
                                                Configuration config)

Factory method to make a GenericAtomicComparer for values of known types

Parameters:

type0 - primitive type of the first operand

type1 - primitive type of the second operand

collator - the collation to be used, if any. This is supplied as a NamedCollation object which encapsulated both the collation URI and the collation itself.

config - the configuration

Returns:

a GenericAtomicComparer for values of known types

getStringCollator

public StringCollator getStringCollator()

Get the underlying string collator

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 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.

Specified by:

comparesEqual 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 equals() method.

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

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.

Specified by:

getComparisonKey in interface AtomicComparer