Class CodepointCollatingComparer

java.lang.Object
net.sf.saxon.sort.CodepointCollatingComparer
All Implemented Interfaces:
Serializable, Comparator, AtomicComparer

public class CodepointCollatingComparer extends Object implements AtomicComparer
An AtomicComparer used for comparing strings, untypedAtomic values, and URIs using the Unicode codepoint collation. A CodepointCollatingComparer is used when it is known in advance that both operands will be of these types, and when the collation is the unicode codepoint collation. This enables all conversions and promotions to be bypassed: the string values of both operands are simply extracted and passed to the collator for comparison.

The difference between using this class and using the underlying CodepointCollator directly is that the compare() method in this class expects two instances of AtomicValue as its operands, whereas the underlying class expects two instances of java.lang.String. This class makes use of the extra information held in the wrapping StringValue object, specifically, the knowledge of whether the string contains surrogate pairs.

Author:
Michael H. Kay
See Also:
  • Method Details

    • getInstance

      public static CodepointCollatingComparer getInstance()
    • compare

      public int compare(Object a, Object 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:
      compare in interface AtomicComparer
      Specified by:
      compare in interface Comparator
      Parameters:
      a - the first object to be compared. This must be either be an instance of AtomicValue, or null to represent an empty sequence. Empty collates before non-empty.
      b - the second object to be compared. This must be either be an instance of AtomicValue, or null to represent an empty sequence.
      Returns:
      invalid input: '<'0 if ainvalid input: '<'b, 0 if a=b, >0 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. The values must be instances of xs:string or a type derived from xs:string. The method will also handle xs:untypedAtomic and xs:anyURI values.
      Specified by:
      comparesEqual in interface AtomicComparer
      Parameters:
      a - the first object to be compared.
      b - the second object to be compared.
      Returns:
      invalid input: '<'0 if ainvalid input: '<'b, 0 if a=b, >0 if a>b
      Throws:
      ClassCastException - if either value is not xs:string or a subtype
    • getComparisonKey

      public ComparisonKey getComparisonKey(AtomicValue a)
      Get a comparison key for an object. This must satisfy the rule that if two objects are equal under the XPath eq operator, then their comparison keys are equal under the Java equals() function, 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