Java repeated character regex with condition

Question

I have large database. I want to check my database capitalize errors. I use this pattern for repeated chars. Pattern works but i need to start and end condition with string.

Pattern:

(\w)\1+

Target String:

Javaaa

result: aaa

I want to add condition to regex; Start with Ja and end with a*. Result **only must be repetead characters.

(I dont want to control programmatically only regex do this if its possible

(I'm do this with String.replaceAll(regex, string) not to Pattern or Matcher class)

this regex result select all. This have condition but result must be aaa if target string Prooo and regex \\bPro\\w*(\\w)\\1+\\w*o\\b then result must be ooo. Your regex result word all — kibar
– kibar, Commented May 9, 2016 at 14:03

Wiktor Stribiżew · Accepted Answer · 2016-05-09 14:12:25Z

2

You may use a lookahead anchored at the leading word boundary:

\b(?=Ja\w*a\b)\w*?((\w)\2+)\w*\b

See the regex demo

Details:

\b - leading word boundary
(?=Ja\w*a\b) - a positive lookahead that requires the whole word to start with Ja, then it can have 0+ word characters and end with a
\w*? - 0+ word characters but as few as possible
((\w)\2+) - Group 1 matching identical consecutive characters
\w* - any remaining word characters (0 or more)
\b - trailing word boundary.

The result you are seeking is in Group 1.

String s = "Prooo\nJavaaa";
Pattern pattern = Pattern.compile("\\b(?=Ja\\w*a\\b)\\w*?((\\w)\\2+)\\w*\\b");
Matcher matcher = pattern.matcher(s);
while (matcher.find()){
    System.out.println(matcher.group(1)); 
}

See the Java demo.

answered May 9, 2016 at 14:12

Wiktor Stribiżew

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7 Comments

kibar Over a year ago

I dont want it because i have large capitalize list have many regex and i use String.replaceAll(regex, string) methods. For example in my list: [ ]{1,}[.]{1,}[ ]{1,}###. (### is splitter).

Wiktor Stribiżew Over a year ago

What is the trouble then? Replace with $1. Are the strings standalone? If they are, just use ^ instead of the leading word boundary, and $ instead of a trailing word boundary. See this demo.

kibar Over a year ago

Yes standalone. For example i want this; In word Javaaa after regex Java if word Prooo after regex Pro. If word Theee do not the anything. I want to only you make the words I have set via String.replaceAll(regex, string) methods.

kibar Over a year ago

Awesome thank you. Finally String s = "Javaaa" String.replaceAll() methods after result is : Java with your regex is it possible?

Wiktor Stribiżew Over a year ago

Well, I am not sure what you need. Please let know what variables are known.

|

Mahendra · Accepted Answer · 2016-05-09 14:32:46Z

1

Another code example (inspired from @Wiktor Stribizew's code ) as per your expected input and output format.

public static void main( String[] args )
{
    String[] input =
        { "Javaaa", "Javaaaaaaaaa", "Javaaaaaaaaaaaaaaaaaa", "Paoooo", "Paoooooooo", "Paooooooooxxxxxxxxx" };
    for ( String str : input )
    {

        System.out.println( "Target String :" + str );
        Pattern pattern = Pattern.compile( "((.)\\2+)" );
        Matcher matcher = pattern.matcher( str );
        while ( matcher.find() )
        {
            System.out.println( "result: " + matcher.group() );
        }
        System.out.println( "---------------------" );
    }
    System.out.println( "Finish" );
}

Output:

Target String :Javaaa
result: aaa
---------------------
Target String :Javaaaaaaaaa
result: aaaaaaaaa
---------------------
Target String :Javaaaaaaaaaaaaaaaaaa
result: aaaaaaaaaaaaaaaaaa
---------------------
Target String :Paoooo
result: oooo
---------------------
Target String :Paoooooooo
result: oooooooo
---------------------
Target String :Paooooooooxxxxxxxxx
result: oooooooo
result: xxxxxxxxx
---------------------
Finish

answered May 9, 2016 at 14:32

Mahendra

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1 Comment

kibar Over a year ago

I dont want it because i have large capitalize list have many regex and i use String.replaceAll(regex, string) methods. For example in my list: [ ]{1,}[.]{1,}[ ]{1,}###. (### is splitter).

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