org.apache.oro.text.regex
Class Util

java.lang.Object
  |
  +--org.apache.oro.text.regex.Util

public final class Util

extends Object

Untamed: The Util class is a holder for useful static utility methods that can be generically applied to Pattern and PatternMatcher instances. This class cannot and is not meant to be instantiated. The Util class currently contains versions of the split() and substitute() methods inspired by Perl's split function and s operation respectively, although they are implemented in such a way as not to rely on the Perl5 implementations of the OROMatcher packages regular expression interfaces. They may operate on any interface implementations conforming to the OROMatcher API specification for the PatternMatcher, Pattern, and MatchResult interfaces. Future versions of the class may include additional utility methods.

A grep method is not included for two reasons:

1. The details of reading a line at a time from an input stream differ in JDK 1.0.2 and JDK 1.1, making it difficult to retain compatibility across both Java releases.
2. Grep style processing is trivial for the programmer to implement in a while loop. Rarely does anyone want to retrieve all occurences of a pattern and then process them. More often a programmer will retrieve pattern matches and process them as they are retrieved, which is more efficient than storing them all in a Vector and then accessing them.

Version:

$Id: Util.java,v 1.5 2001/12/02 06:01:41 markm Exp $

Author:

Daniel F. Savarese

See Also:

Pattern, PatternMatcher

Field Summary

static int	SPLIT_ALL Enabled: A constant passed to the split() methods indicating that all occurrences of a pattern should be used to split a string.
static int	SUBSTITUTE_ALL Enabled: A constant passed to the substitute() methods indicating that all occurrences of a pattern should be substituted.

Constructor Summary

private

Util() The default destructor for the Util class.

Method Summary

static Vector	split(PatternMatcher matcher, Pattern pattern, String input) Enabled: Splits up a String instance into a Vector of all its substrings using a regular expression as the delimiter.
static Vector	split(PatternMatcher matcher, Pattern pattern, String input, int limit) Enabled: Splits up a String instance into strings contained in a Vector of size not greater than a specified limit.
static String	substitute(PatternMatcher matcher, Pattern pattern, Substitution sub, String input) Enabled: Searches a string for a pattern and substitutes only the first occurence of the pattern.
static String	substitute(PatternMatcher matcher, Pattern pattern, Substitution sub, String input, int numSubs) Enabled: Searches a string for a pattern and replaces the first occurrences of the pattern with a Substitution up to the number of substitutions specified by the numSubs parameter.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

SUBSTITUTE_ALL

public static final int SUBSTITUTE_ALL

Enabled: A constant passed to the substitute() methods indicating that all occurrences of a pattern should be substituted.

SPLIT_ALL

public static final int SPLIT_ALL

Enabled: A constant passed to the split() methods indicating that all occurrences of a pattern should be used to split a string.

Constructor Detail

Util

private Util()

The default destructor for the Util class. It is made private to prevent the instantiation of the class.

Method Detail

split

public static Vector split(PatternMatcher matcher,
                           Pattern pattern,
                           String input,
                           int limit)

Enabled: Splits up a String instance into strings contained in a Vector of size not greater than a specified limit. The string is split with a regular expression as the delimiter. The limit parameter essentially says to split the string only on at most the first limit - 1 number of pattern occurences.

This method is inspired by the Perl split() function and behaves identically to it when used in conjunction with the Perl5Matcher and Perl5Pattern classes except for the following difference:

In Perl, if the split expression contains parentheses, the split() method creates additional list elements from each of the matching subgroups in the pattern. In other words:

split("/([,-])/", "8-12,15,18")

produces the Vector containing:

{ "8", "-", "12", ",", "15", ",", "18" }

The OROMatcher split method does not follow this behavior. The following Vector would be produced by OROMatcher:

{ "8", "12", "15", "18" }

To obtain the Perl behavior, use split method in the PerlTools package available from http://www.oroinc.com/ .

Parameters:

matcher - The regular expression matcher to execute the split.

pattern - The regular expression to use as a split delimiter.

input - The String to split.

limit - The limit on the size of the returned Vector. Values <= 0 produce the same behavior as using the SPLIT_ALL constant which causes the limit to be ignored and splits to be performed on all occurrences of the pattern. You should use the SPLIT_ALL constant to achieve this behavior instead of relying on the default behavior associated with non-positive limit values.

Returns:

A Vector containing the substrings of the input that occur between the regular expression delimiter occurences. The input will not be split into any more substrings than the specified limit. A way of thinking of this is that only the first limit - 1 matches of the delimiting regular expression will be used to split the input.

split

public static Vector split(PatternMatcher matcher,
                           Pattern pattern,
                           String input)

Enabled: Splits up a String instance into a Vector of all its substrings using a regular expression as the delimiter. This method is inspired by the Perl split() function and behaves identically to it when used in conjunction with the Perl5Matcher and Perl5Pattern classes except for the following difference:

In Perl, if the split expression contains parentheses, the split() method creates additional list elements from each of the matching subgroups in the pattern. In other words:

split("/([,-])/", "8-12,15,18")

produces the Vector containing:

{ "8", "-", "12", ",", "15", ",", "18" }

The OROMatcher split method does not follow this behavior. The following Vector would be produced by OROMatcher:

{ "8", "12", "15", "18" }

To obtain the Perl behavior, use split method in the PerlTools package available from http://www.oroinc.com/ .

This method is identical to calling:

 split(matcher, pattern, input, Util.SPLIT_ALL);
 

Parameters:

matcher - The regular expression matcher to execute the split.

pattern - The regular expression to use as a split delimiter.

input - The String to split.

Returns:

A Vector containing all the substrings of the input that occur between the regular expression delimiter occurences.

substitute

public static String substitute(PatternMatcher matcher,
                                Pattern pattern,
                                Substitution sub,
                                String input,
                                int numSubs)

Enabled: Searches a string for a pattern and replaces the first occurrences of the pattern with a Substitution up to the number of substitutions specified by the numSubs parameter. A numSubs value of SUBSTITUTE_ALL will cause all occurrences of the pattern to be replaced.

Parameters:

matcher - The regular expression matcher to execute the pattern search.

pattern - The regular expression to search for and substitute occurrences of.

sub - The Substitution used to substitute pattern occurences.

input - The String on which to perform substitutions.

numSubs - The number of substitutions to perform. Only the first numSubs patterns encountered are substituted. If you want to substitute all occurences set this parameter to SUBSTITUTE_ALL .

Returns:

A String comprising the input string with the substitutions, if any, made. If no substitutions are made, the returned String is the original input String.

substitute

public static String substitute(PatternMatcher matcher,
                                Pattern pattern,
                                Substitution sub,
                                String input)

Enabled: Searches a string for a pattern and substitutes only the first occurence of the pattern.

This method is identical to calling:

 substitute(matcher, pattern, sub, input, 1);
 

Parameters:

matcher - The regular expression matcher to execute the pattern search.

pattern - The regular expression to search for and substitute occurrences of.

sub - The Substitution used to substitute pattern occurences.

input - The String on which to perform substitutions.

Returns:

A String comprising the input string with the substitutions, if any, made. If no substitutions are made, the returned String is the original input String.