Class EqualityComparer

  • All Implemented Interfaces:
    java.io.Serializable, AtomicComparer

    public class EqualityComparer
    extends java.lang.Object
    implements AtomicComparer
    A comparer for comparing two atomic values where (a) equals is defined, and is implemented using the Java equals() method, and (b) ordering is not defined, and results in a dynamic error.
    See Also:
    Serialized Form
    • Method Detail

      • getInstance

        public static EqualityComparer 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. 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:
        java.lang.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:
        java.lang.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