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java.lang.Object net.sf.saxon.expr.sort.AtomicSortComparer
public class AtomicSortComparer
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. 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.
Field Summary | |
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static StructuredQName |
COLLATION_KEY_NaN
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Constructor Summary | |
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protected |
AtomicSortComparer(StringCollator collator,
int itemType,
XPathContext context)
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Method Summary | |
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int |
compareAtomicValues(AtomicValue a,
AtomicValue b)
Compare two AtomicValue objects according to the rules for their data type. |
protected int |
compareNonComparables(AtomicValue a,
AtomicValue b)
Compare two values that are known to be non-comparable. |
boolean |
comparesEqual(AtomicValue a,
AtomicValue b)
Compare two AtomicValue objects for equality according to the rules for their data type. |
StringCollator |
getCollator()
Get the collation used by this AtomicComparer if any |
ComparisonKey |
getComparisonKey(AtomicValue a)
Get a comparison key for an object. |
int |
getItemType()
Get the requested item type |
StringCollator |
getStringCollator()
Get the underlying StringCollator |
static AtomicComparer |
makeSortComparer(StringCollator 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) |
AtomicComparer |
provideContext(XPathContext context)
Supply the dynamic context in case this is needed for the comparison |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
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public static StructuredQName COLLATION_KEY_NaN
Constructor Detail |
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protected AtomicSortComparer(StringCollator collator, int itemType, XPathContext context)
Method Detail |
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public static AtomicComparer makeSortComparer(StringCollator collator, int itemType, XPathContext context)
collator
- Collating comparer to be used when comparing strings. This argument may be null
if the itemType excludes the possibility of comparing strings. If the method is called at compile
time, this should be a SimpleCollation so that it can be cloned at run-time.itemType
- the primitive item type of the values to be comparedcontext
- Dynamic context (may be an EarlyEvaluationContext)
public StringCollator getCollator()
AtomicComparer
getCollator
in interface AtomicComparer
public AtomicComparer provideContext(XPathContext context)
provideContext
in interface AtomicComparer
context
- the dynamic evaluation context
public StringCollator getStringCollator()
public int getItemType()
public int compareAtomicValues(AtomicValue a, AtomicValue b) throws NoDynamicContextException
compareAtomicValues
in interface AtomicComparer
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.
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.protected int compareNonComparables(AtomicValue a, AtomicValue b)
Value.INDETERMINATE_ORDERING
public boolean comparesEqual(AtomicValue a, AtomicValue b) throws NoDynamicContextException
comparesEqual
in interface AtomicComparer
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.
ClassCastException
- if the objects are not comparable
NoDynamicContextException
public ComparisonKey getComparisonKey(AtomicValue a) throws NoDynamicContextException
getComparisonKey
in interface AtomicComparer
NoDynamicContextException
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