Package net.sf.saxon.expr.sort
Class EmptyGreatestComparer
java.lang.Object
net.sf.saxon.expr.sort.EmptyGreatestComparer
- All Implemented Interfaces:
AtomicComparer
A Comparer that modifies a base comparer by sorting empty key values and NaN values last (greatest),
as opposed to the default which sorts them first.
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Constructor Summary
ConstructorsConstructorDescriptionEmptyGreatestComparer
(AtomicComparer baseComparer) Create an EmptyGreatestComparer -
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 the underlying comparer (which compares empty least)Get the collation used by this AtomicComparer if anyprovideContext
(XPathContext context) Supply the dynamic context in case this is needed for the comparisonsave()
Create a string representation of this AtomicComparer that can be saved in a compiled package and used to reconstitute the AtomicComparer when the package is reloaded
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Constructor Details
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EmptyGreatestComparer
Create an EmptyGreatestComparer- Parameters:
baseComparer
- the comparer used to compare non-empty values (which typically sorts empty as least)
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Method Details
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getBaseComparer
Get the underlying comparer (which compares empty least)- Returns:
- the base comparer
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getCollator
Description copied from interface:AtomicComparer
Get the collation used by this AtomicComparer if any- Specified by:
getCollator
in interfaceAtomicComparer
- Returns:
- the collation used for comparing strings, or null if not applicable
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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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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:
- <0 if a<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.b
- the second object to be compared.- Returns:
- true if the values are equal, false if not
- Throws:
ClassCastException
- if the objects are not comparableNoDynamicContextException
- if no dynamic context has been supplied, and a dynamic context is needed (for example, because the comparison uses the implicit timezone)
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save
Create a string representation of this AtomicComparer that can be saved in a compiled package and used to reconstitute the AtomicComparer when the package is reloaded- Specified by:
save
in interfaceAtomicComparer
- Returns:
- a string representation of the AtomicComparer
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