Solved

Java replaceAll regex

Posted on 2009-04-02
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Last Modified: 2013-11-23

 Hi Experts,
 
    I want to replace the following string embeded in an input line
   AFunctionName[startPosition , endPosition]  
   with
   SUBSTR(AFunctionName, startPosition , endPosition)
 
   match requirements:
   1.  space in AFunctionName[startPosition , endPosition],  before and after comma ","  is option;
   2. All names, AFunctionName, startPosition, endPosition are made of  word characters

   I wrote a method to parse it doesn't work, any help is appreciated.

0
Comment
Question by:SarahDeng
  • 4
  • 3
7 Comments
 
LVL 40

Accepted Solution

by:
RQuadling earned 300 total points
ID: 24055081
Try this ...
StringBuffer resultString = new StringBuffer();

try {

	Pattern regex = Pattern.compile("(\\w+)\\[(\\w+) , (\\w+)\\]", Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE | Pattern.MULTILINE);

	Matcher regexMatcher = regex.matcher(subjectString);

	while (regexMatcher.find()) {

		try {

			// You can vary the replacement text for each match on-the-fly

			regexMatcher.appendReplacement(resultString, "SUBSTR($1, $2, $3)");

		} catch (IllegalStateException ex) {

			// appendReplacement() called without a prior successful call to find()

		} catch (IllegalArgumentException ex) {

			// Syntax error in the replacement text (unescaped $ signs?)

		} catch (IndexOutOfBoundsException ex) {

			// Non-existent backreference used the replacement text

		} 

	}

	regexMatcher.appendTail(resultString);

} catch (PatternSyntaxException ex) {

	// Syntax error in the regular expression

}

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0
 

Author Closing Comment

by:SarahDeng
ID: 31566024
Can't expect better and quicker than this!
0
 

Author Comment

by:SarahDeng
ID: 24055341
Hi RQuadling,
Oops! there is one exception.
It doesn't work when there is no space before and after the ","
example:
 No space in AFunctionName[startPosition,endPosition],  before and after comma ","
I change the expression to the following, it doesn't work for me.  Could you help again? Thanks!
 "(\\w+)\\[(\\w+)(\\s*),(\\s*) (\\w+)\\]",
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LVL 40

Expert Comment

by:RQuadling
ID: 24055392
Try this ...
StringBuffer resultString = new StringBuffer();

try {

	Pattern regex = Pattern.compile("(\\w+)\\[(\\w+)\\s+?,\\s+?(\\w+)\\]", Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE | Pattern.MULTILINE);

	Matcher regexMatcher = regex.matcher(subjectString);

	while (regexMatcher.find()) {

		try {

			// You can vary the replacement text for each match on-the-fly

			regexMatcher.appendReplacement(resultString, "SUBSTR($1, $2, $3)");

		} catch (IllegalStateException ex) {

			// appendReplacement() called without a prior successful call to find()

		} catch (IllegalArgumentException ex) {

			// Syntax error in the replacement text (unescaped $ signs?)

		} catch (IndexOutOfBoundsException ex) {

			// Non-existent backreference used the replacement text

		} 

	}

	regexMatcher.appendTail(resultString);

} catch (PatternSyntaxException ex) {

	// Syntax error in the regular expression

}

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0
 

Author Comment

by:SarahDeng
ID: 24055491
I tried... It doesn't work with the case that no space before and after the ","
Like this.
string_variable[startPosition,endPostion]

0
 

Author Comment

by:SarahDeng
ID: 24055529
Changed the expression to
"(\\w+)\\[(\\w+)\\s*,\\s*(\\w+)\\]"
it works.
Can you explain why?
0
 
LVL 40

Expert Comment

by:RQuadling
ID: 24057754
Ah Yes.

\s+\s*

Options: case insensitive; ^ and $ match at line breaks

Match a single character that is a whitespace character (spaces, tabs, line breaks, etc.) «\s+?»
   Between one and unlimited times, as few times as possible, expanding as needed (lazy) «+?»

Match a single character that is a whitespace character (spaces, tabs, line breaks, etc.) «\s*»
   Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «*»


I was assuming at least 1 space. Sorry.
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