Package net.sf.saxon.sort
Class AtomicSortComparer
java.lang.Object
net.sf.saxon.sort.AtomicSortComparer
- All Implemented Interfaces:
Serializable
,AtomicComparer
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.
- Author:
- Michael H. Kay
- See Also:
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Field Summary
Fields -
Method Summary
Modifier and TypeMethodDescriptionint
Compare two AtomicValue objects according to the rules for their data type.boolean
Compare two AtomicValue objects for equality according to the rules for their data type.Get a comparison key for an object.int
Get the requested item typeGet the underlying StringCollatorstatic 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)provideContext
(XPathContext context) Supply the dynamic context in case this is needed for the comparison
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Field Details
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COLLATION_KEY_NaN
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Method Details
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makeSortComparer
public 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)- Parameters:
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 NamedCollation 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)- Returns:
- a suitable AtomicComparer
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provideContext
Supply the dynamic context in case this is needed for the comparison- Specified by:
provideContext
in interfaceAtomicComparer
- 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
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getStringCollator
Get the underlying StringCollator- Returns:
- the underlying collator
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getItemType
public int getItemType()Get the requested item type- Returns:
- the item type
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compareAtomicValues
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 interfaceAtomicComparer
- Parameters:
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.- Returns:
- invalid input: '<'0 if ainvalid input: '<'b, 0 if a=b, >0 if a>b
- Throws:
ClassCastException
- if the objects are not comparableNoDynamicContextException
- 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.
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comparesEqual
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 interfaceAtomicComparer
- 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:
ClassCastException
- if the objects are not comparableNoDynamicContextException
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getComparisonKey
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 interfaceAtomicComparer
- Throws:
NoDynamicContextException
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