Class DescendingComparer

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

    public class DescendingComparer
    extends java.lang.Object
    implements AtomicComparer, java.io.Serializable
    A Comparer used for comparing descending keys. This simply returns the inverse of the result delivered by the base comparer.
    See Also:
    Serialized Form
    • Constructor Detail

      • DescendingComparer

        public DescendingComparer​(AtomicComparer base)
    • Method Detail

      • getBaseComparer

        public AtomicComparer getBaseComparer()
        Get the underlying (ascending) comparer
        Returns:
        the underlying (ascending) comparer
      • 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
        Throws:
        NoDynamicContextException - if the context is an "early evaluation" (compile-time) context
      • compareAtomicValues

        public int compareAtomicValues​(AtomicValue a,
                                       AtomicValue b)
                                throws NoDynamicContextException
        Compare two objects.
        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 of the wrong type for this Comparer
        NoDynamicContextException - if this comparer required access to dynamic context information, notably the implicit timezone, and this information is not available. In general this happens if a context-dependent comparison is attempted at compile-time, and it signals the compiler to generate code that tries again at run-time.
      • comparesEqual

        public boolean comparesEqual​(AtomicValue a,
                                     AtomicValue b)
                              throws NoDynamicContextException
        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:
        java.lang.ClassCastException - if the objects are not comparable
        NoDynamicContextException
      • getComparisonKey

        public ComparisonKey getComparisonKey​(AtomicValue a)
                                       throws NoDynamicContextException
        Get a comparison key for an object. This must satisfy the rule that if two objects are equal according to the XPath eq operator, then their comparison keys are equal according to 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
        Throws:
        NoDynamicContextException