Class GenericAtomicComparer

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

    public class GenericAtomicComparer
    extends java.lang.Object
    implements AtomicComparer, java.io.Serializable
    An AtomicComparer 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.
    Author:
    Michael H. Kay
    See Also:
    Serialized Form
    • Constructor Detail

      • GenericAtomicComparer

        public GenericAtomicComparer​(StringCollator collator,
                                     XPathContext conversionContext)
        Create an GenericAtomicComparer
        Parameters:
        collator - the collation to be used
        conversionContext - a context, used when converting untyped atomic values to the target type.
    • Method Detail

      • makeAtomicComparer

        public static AtomicComparer makeAtomicComparer​(BuiltInAtomicType type0,
                                                        BuiltInAtomicType type1,
                                                        StringCollator collator,
                                                        XPathContext context)
        Factory method to make a GenericAtomicComparer for values of known types
        Parameters:
        type0 - primitive type of the first operand
        type1 - primitive type of the second operand
        collator - the collation to be used, if any. This is supplied as a SimpleCollation object which encapsulated both the collation URI and the collation itself.
        context - the dynamic context
        Returns:
        a GenericAtomicComparer for values of known types
      • 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
      • getStringCollator

        public StringCollator getStringCollator()
        Get the underlying string collator
        Returns:
        the string collator
      • compareAtomicValues

        public int compareAtomicValues​(AtomicValue a,
                                       AtomicValue b)
                                throws NoDynamicContextException
        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 a < b, 0 if a = b, >0 if a > b
        Throws:
        java.lang.ClassCastException - if the objects are not comparable
        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 as if they were strings; if different semantics are wanted, the conversion must be done by the caller.
        Specified by:
        comparesEqual in interface AtomicComparer
        Parameters:
        a - the first object to be compared. 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:
        <0 if a0 if a>b
        Throws:
        java.lang.ClassCastException - if the objects are not comparable
        NoDynamicContextException
      • 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