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## net.sf.saxon.expr.sort
Class TextComparer

    java.lang.Object
      net.sf.saxon.expr.sort.TextComparer

All Implemented Interfaces:
  Serializable, AtomicComparer

    public class TextComparer

extends Object
implements AtomicComparer, Serializable

A Comparer used for comparing sort keys when data-type="text". The items to be compared are converted to strings, and the strings are then compared using an underlying collator

Author:
  Michael H. Kay
See Also:
  Serialized Form

Constructor Summary
`TextComparer(AtomicComparer baseComparer)`

Method Summary
`int` | `compareAtomicValues(AtomicValue a, AtomicValue b)` Compare two Items by converting them to strings and comparing the string values.
`boolean` | `comparesEqual(AtomicValue a, AtomicValue b)` Compare two AtomicValue objects for equality according to the rules for their data type.
`AtomicComparer` | `getBaseComparer()` Get the underlying comparer (which doesn't do conversion to string)
`StringCollator` | `getCollator()` Get the collation used by this AtomicComparer if any
`ComparisonKey` | `getComparisonKey(AtomicValue a)` Get a comparison key for an object.
`AtomicComparer` | `provideContext(XPathContext context)` Supply the dynamic context in case this is needed for the comparison

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### TextComparer

    public TextComparer(AtomicComparer baseComparer)

Method Detail

### getBaseComparer

    public AtomicComparer getBaseComparer()

  Get the underlying comparer (which doesn't do conversion to string)

### 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
  Throws:
    `NoDynamicContextException` - if the context is an "early evaluation" (compile-time) context

### compareAtomicValues

    public int compareAtomicValues(AtomicValue a,
                                   AtomicValue b)
                            throws ClassCastException,
                                   NoDynamicContextException

  Compare two Items by converting them to strings and comparing the string values.

  Specified by:
    `compareAtomicValues` in interface `AtomicComparer`
  Parameters:
    `a` - the first Item to be compared.
    `b` - the second Item to be compared.
  Returns:
    <0 if a 0 if a>b
  Throws:
    `ClassCastException` - if the objects are not Items, or are items that cannot be convered to strings (e.g. QNames)
    `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 by converting to the type of the other operand.

  Specified by:
    `comparesEqual` in interface `AtomicComparer`
  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 comparable
    `NoDynamicContextException`

### getComparisonKey

    public ComparisonKey getComparisonKey(AtomicValue a)
                                   throws NoDynamicContextException

  Get a comparison key for an object. This must satisfy the rule that if two objects are equal according to the XPath eq operator, then their comparison keys are equal according to the Java equals() method, 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`
  Throws:
    `NoDynamicContextException`

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Copyright (c) 2004-2010 Saxonica Limited. All rights reserved.