net.sf.saxon.sort

Class DoubleSortComparer

java.lang.Object

net.sf.saxon.sort.DoubleSortComparer

All Implemented Interfaces:

Serializable, Comparator, AtomicComparer

public class DoubleSortComparer
extends Object
implements AtomicComparer

A Comparator used for sorting values that are known to be numeric. It also supports a separate method for getting a collation key to test equality of items. This comparator treats NaN values as equal to each other, and less than any other value.

Author:

Michael H. Kay

See Also:

Serialized Form

Method Summary

Modifier and Type	Method and Description
int	compare(Object a, Object b) Compare two AtomicValue objects according to the rules for their data type.
boolean	comparesEqual(AtomicValue a, AtomicValue b) Test whether two values compare equal.
ComparisonKey	getComparisonKey(AtomicValue a) Get a comparison key for an object.
static DoubleSortComparer	getInstance()

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Comparator

comparing, comparing, comparingDouble, comparingInt, comparingLong, equals, naturalOrder, nullsFirst, nullsLast, reversed, reverseOrder, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

Method Detail

getInstance

public static DoubleSortComparer getInstance()

compare

public int compare(Object a,
                   Object b)

Compare two AtomicValue objects according to the rules for their data type.

Specified by:

compare in interface Comparator

Specified by:

compare in interface AtomicComparer

Parameters:

a - the first object to be compared. It is intended that this should normally 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)

Test whether two values compare equal. Note that for this comparer, NaN is considered equal to itself

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:

true if the values are equal, false if not

getComparisonKey

public ComparisonKey getComparisonKey(AtomicValue a)

Get a comparison key for an object. This must satisfy the rule that if two objects are equal as defined by the XPath eq operator, then their comparison keys are equal as defined by the Java equals() method, 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