Class GenericAtomicComparer

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

public class GenericAtomicComparer extends Object implements AtomicComparer, 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:
  • Constructor Details

    • GenericAtomicComparer

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

    • 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 NamedCollation object which encapsulated both the collation URI and the collation itself.
      context - the dynamic context
      Returns:
      a GenericAtomicComparer for values of known types
    • 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:
      invalid input: '<'0 if a invalid input: '<' b, 0 if a = b, >0 if a > b
      Throws:
      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:
      invalid input: '<'0 if ainvalid input: '<'b, 0 if a=b, >0 if a>b
      Throws:
      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