Class AtomicSortComparer

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

public class AtomicSortComparer extends Object implements AtomicComparer
A Comparator 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. The AtomicSortComparer is identical to the GenericAtomicComparer except for its handling of NaN: it treats NaN values as lower than any other value, and as equal to each other.
Author:
Michael H. Kay
See Also:
  • Field Details

    • COLLATION_KEY_NaN

      public static StringValue COLLATION_KEY_NaN
  • Method Details

    • makeSortComparer

      public static AtomicComparer makeSortComparer(Comparator collator, int itemType, XPathContext context)
      Factory method to get an atomic comparer suitable for sorting or for grouping (operations in which NaN is considered equal to NaN)
      Parameters:
      collator - Collating comparer to be used when comparing strings
      itemType - Primitive item type of the values to be compared
      context - Dynamic context (may be an EarlyEvaluationContext)
      Returns:
      a suitable AtomicComparer
    • 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. 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:
      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 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:
      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