net.sf.webcat
Class StringNormalizer

java.lang.Object
  java.util.AbstractCollection<E>
      java.util.AbstractList<E>
          java.util.ArrayList<StringNormalizer.NormalizerRule>
              net.sf.webcat.StringNormalizer

All Implemented Interfaces:

Serializable, Cloneable, Iterable<StringNormalizer.NormalizerRule>, Collection<StringNormalizer.NormalizerRule>, List<StringNormalizer.NormalizerRule>, RandomAccess

public class StringNormalizer
extends ArrayList<StringNormalizer.NormalizerRule>

This class represents a programmable string "normalizing" engine that can be used to convert strings into a canonical form, say, before comparing strings for equality or something. Basically, a normalizer is a list of zero or more rules, or transformations. The normalize(String) method can be used to apply the entire set of transformations to a given string.

For example, you can build a string normalizer that replaces all sequences of one or more whitespace characters by a single space character, trims any leading or trailing space, and converts a string to lower case. This class provides a number of predefined transformations in the StringNormalizer.StandardRule enumeration. Some examples:

  // An "identity" transformation that does nothing:
  StringNormalizer norm1 = new StringNormalizer();
  // norm1.normalize(...) returns its argument unchanged

  // A "lower case" normalizer:
  StringNormalizer norm2 = new StringNormalizer(
      StringNormalizer.StandardRule.IGNORE_CAPITALIZATION);
  // norm2.normalize(...) returns a lower case version of its argument

  // self-explanatory:
  StringNormalizer norm3 = new StringNormalizer(
      StringNormalizer.StandardRule.IGNORE_CAPITALIZATION,
      StringNormalizer.StandardRule.IGNORE_PUNCTUATION);

  // A "standard" normalizer:
  StringNormalizer norm4 = new StringNormalizer(true);
  // norm4.normalize(...) returns its contents with all punctuation
  // characters removed, all letters converted to lower case, all
  // whitespace sequences replaced by single spaces, all MS-DOS or
  // Mac line terminators replaced by "\n"'s, and all leading and
  // trailing whitespace removed.
  

Note that string normalizers that contain multiple rules apply those rules in order (i.e., in the order added, or the List order of this class). This may produce inconsistent results if you are not careful when you add your rules.

Version:

$Id: StringNormalizer.java,v 1.2 2007/09/15 02:04:16 stedwar2 Exp $

Author:

Stephen Edwards

See Also:

Serialized Form

Nested Class Summary

static interface	StringNormalizer.NormalizerRule This interface defines what it means to be a normalizer rule: an object having an appropriate StringNormalizer.NormalizerRule.normalize(String) method.
static class	StringNormalizer.RegexNormalizerRule A highly reusable concrete implementation of StringNormalizer.NormalizerRule that applies a series of regular expression substitutions.
static class	StringNormalizer.StandardRule This enumeration defines the set of predefined transformation rules.

Constructor Summary

StringNormalizer()
Creates a new StringNormalizer object containing no rules (the "identity" normalizer).

StringNormalizer(boolean useStandardRules)
Creates a new StringNormalizer object, optionally containing the standard set of rules.

StringNormalizer(Collection<? extends StringNormalizer.NormalizerRule> rules)
Creates a new StringNormalizer object containing the given set of rules.

StringNormalizer(StringNormalizer.NormalizerRule... rules)
Creates a new StringNormalizer object containing the given set of rules.

StringNormalizer(StringNormalizer.StandardRule... rules)
Creates a new StringNormalizer object containing the given set of rules.

Method Summary

boolean	add(StringNormalizer.NormalizerRule rule) Add the specified rule.
void	add(StringNormalizer.StandardRule rule) Add the specified standard rule, as defined in StringNormalizer.StandardRule.
void	addStandardRules() Add the standard set of rules.
String	normalize(String content) Normalize a string by applying a set of normalization rules (transformations).
void	remove(StringNormalizer.StandardRule rule) Remove the specified standard rule, as defined in StringNormalizer.StandardRule.
static StringNormalizer.NormalizerRule	standardRule(StringNormalizer.StandardRule rule) Retrieve a standard rule by name.

Methods inherited from class java.util.ArrayList

add, addAll, addAll, clear, clone, contains, ensureCapacity, get, indexOf, isEmpty, lastIndexOf, remove, remove, set, size, toArray, toArray, trimToSize

Methods inherited from class java.util.AbstractList

equals, hashCode, iterator, listIterator, listIterator, subList

Methods inherited from class java.util.AbstractCollection

containsAll, removeAll, retainAll, toString

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.List

containsAll, equals, hashCode, iterator, listIterator, listIterator, removeAll, retainAll, subList

Constructor Detail

StringNormalizer

public StringNormalizer()

Creates a new StringNormalizer object containing no rules (the "identity" normalizer).

StringNormalizer

public StringNormalizer(boolean useStandardRules)

Creates a new StringNormalizer object, optionally containing the standard set of rules. The standard set is all those in StringNormalizer.StandardRule exception the OPT_* rules.

Parameters:

useStandardRules - If true, the set of standard (non-OPT_*) rules will be used. If false, an "identity" normalizer will be produced instead.

StringNormalizer

public StringNormalizer(StringNormalizer.StandardRule... rules)

Creates a new StringNormalizer object containing the given set of rules.

Parameters:

rules - a (variable-length) comma-separated sequence of rules to add

StringNormalizer

public StringNormalizer(StringNormalizer.NormalizerRule... rules)

Creates a new StringNormalizer object containing the given set of rules.

Parameters:

rules - a (variable-length) comma-separated sequence of rules to add

StringNormalizer

public StringNormalizer(Collection<? extends StringNormalizer.NormalizerRule> rules)

Creates a new StringNormalizer object containing the given set of rules.

Parameters:

rules - a collection of rules to add (could be another StringNormalizer, or any other kind of collection)

Method Detail

normalize

public String normalize(String content)

Normalize a string by applying a set of normalization rules (transformations).

Parameters:

content - The string to transform

Returns:

The result after all rules have been applied

addStandardRules

public void addStandardRules()

Add the standard set of rules. The standard set is all those in StringNormalizer.StandardRule exception the OPT_* rules.

add

public void add(StringNormalizer.StandardRule rule)

Add the specified standard rule, as defined in StringNormalizer.StandardRule. Note that you can also use the inherited List.add(Object) method to add custom NormalizerRule objects.

Parameters:

rule - The rule to add

add

public boolean add(StringNormalizer.NormalizerRule rule)

Add the specified rule. For efficiency, only adds the rule if it is not already present in this normalizer.

Specified by:

add in interface Collection<StringNormalizer.NormalizerRule>

Specified by:

add in interface List<StringNormalizer.NormalizerRule>

Overrides:

add in class ArrayList<StringNormalizer.NormalizerRule>

Parameters:

rule - The rule to add

Returns:

True if the rule was added, or false if it is already present

remove

public void remove(StringNormalizer.StandardRule rule)

Remove the specified standard rule, as defined in StringNormalizer.StandardRule. Note that you can also use the inherited List.remove(Object) method to remove other kinds of NormalizerRule objects.

Parameters:

rule - The rule to remove

standardRule

public static StringNormalizer.NormalizerRule standardRule(StringNormalizer.StandardRule rule)

Retrieve a standard rule by name.

Parameters:

rule - the rule to retrieve

Returns:

The corresponding StringNormalizer.NormalizerRule