net.sf.saxon.expr.sort
Class ComparableAtomicValueComparer

java.lang.Object
  extended by net.sf.saxon.expr.sort.ComparableAtomicValueComparer
All Implemented Interfaces:
Serializable, AtomicComparer
Direct Known Subclasses:
DecimalSortComparer

public class ComparableAtomicValueComparer
extends Object
implements AtomicComparer

A comparer for comparing two "ordinary" atomic values, where the values implement the Comparable interface and the equals() method with the appropriate XPath semantics. This rules out use of collations, conversion of untyped atomic values, and context dependencies such as implicit timezone.

See Also:
Serialized Form

Constructor Summary
protected ComparableAtomicValueComparer()
           
 
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.
 StringCollator getCollator()
          Get the collation used by this AtomicComparer if any
 ComparisonKey getComparisonKey(AtomicValue a)
          Get a comparison key for an object.
static ComparableAtomicValueComparer getInstance()
          Get the singleton instance of this class
 AtomicComparer provideContext(XPathContext context)
          Supply the dynamic context in case this is needed for the comparison
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ComparableAtomicValueComparer

protected ComparableAtomicValueComparer()
Method Detail

getInstance

public static ComparableAtomicValueComparer 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. This must be an AtomicValue and it must implement Comparable with context-free XPath comparison semantics
b - the second object to be compared. This must be an AtomicValue and it must implement Comparable with context-free XPath comparison semantics
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. 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.

Specified by:
getComparisonKey in interface AtomicComparer


Copyright (c) 2004-2011 Saxonica Limited. All rights reserved.